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Mineral composition of leaves in relation to degree of granulation in sweet orange
Scientia Horticulturae, 9 (1978) 357--367
357
Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
MINERAL COMPOSITION OF LEAVES IN RELATION TO DEGREE OF GRANULATION IN SWEET ORANGE
S.K. MUNSHI, R A G H B I R SINGH, V.K. VIJ and J.S.J A W A N D A
Regional Fruit Research Station, Punjab Agricultural University, A bohar 152116 (India) (First received 3 April 1978; in revised form 19 June 1978)
ABSTRACT Munshi, S.K., Singh, R., Vij, V.K. and Jawanda, J.S., 1978. Mineral composition of leaves in relation to degree of granulation in sweet orange. Scientia Hortic., 9: 357--367. Studies on the possible relationship between macro- as well as micro-elements in the leaves of fruiting-shoots and in the fruits at different degrees of granulation, were carried out in 2 cultivars of sweet orange, viz. 'Musambi' and 'Blood Red', by following a special leaf-sampling technique. The data have revealed accumulation of N, P, K, Mg, Zn and Cu, a decrease of Ca, Fe and B, and no change in Mn content in the leaves as the granulation progressed in both cultivars. Varietal variation influenced the level of N, K, Mg, Mn and B in the leaves. The metabolism of each element has been discussed in the light of various agro-climatic conditions prevailing in this area.
INTRODUCTION
The problem of granulation in fruits has assumed serious proportions in the citrus orchards of north India, particularly those in arid, irrigated tracts of Punjab. A number of workers (Lloyd, 1961; Hield and Erickson, 1962; Awasthi, 1969; Manchanda, 1974) have studied different aspects of the problem, but so far no satisfactory solution has been found. A few researchers (Sinclair and Jolliffe, 1961; Lloyd, 1961; Awasthi, 1969) have shown that granulated fruits contained excessive amounts of mineral constituents. Information on the relationship of both macro- and micro-nutrients in the granulated fruits has recently been presented by Munshi et al. (1978a). According to another study (Munshi et al., 1978b), low P and high K and B in the leaves, and soil characteristics like loamy to clay--loam texture and excess free lime, appeared to aggravate the granulation. The nutritional status in citrus has been recognised as an important tool for determining the vigour of the plants (Embleton et al., 1963; Chapman, 1968). It is felt that studies on the relationship between mineral composition of the leaves and degree of granulation in the fruits can contribute to a proper understanding of the cause(s) of this physiological disorder. The present studies were therefore attempted to reveal this relationship.
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MATERIALS AND METHODS
Twelve~year old trees of 'Musambi' and 'Blood Red' cultivars of s~veet orange (Citrus sinensis (L.) Obseck), raised on rough lemon (Citrus j a m bhiri Lush. ),
were selected in the citrus plantations at our research station. The fruits (about 1000) were tagged in the first week of September and the leaves of corresponding branches were collected separately in small paper bags. The leaves so obtained were washed, dried and stored as detailed below. At the end of the ripeningperiod, i.e. early December in the case of 'Musambi' and the end of December for 'Blood Red', the tagged fruits were cut to assess the extent of granulation. The leaf samples collected in September were categorised and grouped according to the percentage of granulation in the fruit. Similarly, leaves were collected from the other (untagged) fruiting-shoots in December, depending on the maturity of fruits in each cultivar, and grouped according to the percentage of granulation. The leaf samples were collected in 1973 and 1974 and were grouped into 5 grades on the basis of severity of granulation of the fruits, viz. 0--5, 6--15, 16--40, 41--70 and above 70%. The assessment for the degree of granulation was carried o u t b y cutting thin sections (0.5 cm thickness) from the stem end extending perpendicularly d o w n to the stylar end. The percentage of granulation was measured b y visual inspection and calculated after Munshi et al. (1978c). There were 3 replications and critical differences (C.D.) were calculated from a randomised block design. Usually, the leaf samples collected from non-fruiting shoots are preferred over fruiting shoots for a number of reasons (Embleton et al., 1963). However, the present studies were purposely carried o u t on the leaves taken from the fruiting shoots to elucidate the nutritional imbalance, if any, occurring in the fruits/fruiting twigs with the development of granulation. Therefore, the standards fixed b y Chapman (1960) and Embleton et al. (1963) have been used for comparison. The leaves were immediately brought to the laboratory, washed, dried and ground to a powder, following the procedure of Mann et al. (1978). Total nitrogen was estimated b y a micro-Kjeldahl m e t h o d and all other elements on an emission s p e c t r o p h o t o m e t e r in the Plant Analyses Laboratory, Department of Soils, Punjab Agricultural University, Ludhiana. RESULTS
Nitrogen. - - Total N c o n t e n t in the leaves of shoots bearing from normal to
granulated fruits increased in September in both cultivars (Table 1). The leaves collected in December revealed a similar trend although the data for 1974 was found to be non-significant. Total N was also lower in the leaves during 1974 as compared to the previou~ year. Phosphorus. - - The level of P in the leaves collected from granulated (> 70%)
fruit~bearing shoots was found to be significantly higher than that of normal
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TABLE 1 Nitrogen content (%) in the leaves of shoots bearing fruits of different percentages of granulation Cultivar
'Musambi'
Percentage granulation
0--5 6--15 16--40 41--70 > 70
CD at 5% 'Blood Red'
0--5 6--15 16--40 41--70 > 70
CD at 5%
September
December
1973
1974
Mean
1973
1974
Mean
2.62 2.71 2.71 2.68 2.72
2.27 2.30 2.30 2.38 2.41
2.45 2.51 2.51 2.53 2.57
2.71 2.71 2.80 2.85 2.89
2.21 2.23 2.30 2.33 2.34
2.46 2.47 2.55 2.59 2.62
NS
0.12
0.13
NS
2.62 2.75 2.80 2.85 2.87
2.27 2.30 2.32 2.35 2.37
2.60 2.62 2.84 2.85 2.89
2.28 2.31 2.33 2.32 2.32
0.16
NS
0.13
NS
2.45 2.53 2.56 2.60 2.62
2.44 2.47 2.59 2.59 2.61
shoots (0--5%) in 'Musambi' (December) and 'Blood Red' (September and December). The leaves collected in September and December did not show any variation in P content (Table 2). TABLE 2 Phosphorus content (%) in the leaves of shoots bearing fruits of different percentages of granulation Cultivar
'Musambi'
Percentage granulation
0--5 6--15 16--40 41--70 > 70
CD at 5% 'Blood Red'
CD at 5%
0--5 6--15 16--40 41--70 > 70
September
December
1973
1974
Mean
1973
1974
Mean
0.150 0.150 0.150 0.160 0.150
0.160 0.160 0.160 0.160 0.160
0.155 0.155 0.155 0.160 0.155
0.140 0.140 0.140 0.150 0.170
0.150 0.160 0.160 0.180 0.180
0.145 0.150 0.150 0.165 0.175
NS
NS
0.018
0.023
0.135 0.150 0.160 0.180 0.180
0.130 0.150 0.150 0.160 0.160
0.145 0.150 0.160 0.160 0.170
0.150 0.150 0.150 0.160 0.160
0.021
0.023
0.021
NS
0.133 0.150 0.155 0.170 0.170
0.148 0.150 0.155 0.160 0.165
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- - T h e d a t a p r e s e n t e d in T a b l e 3 reveal t h a t K c o n t e n t in t h e leaves increased significantly, progressively w i t h the degree o f g r a n u l a t i o n in b o t h ' M u s a m b i ' a n d ' B l o o d R e d ' . P o t a s s i u m c o n t e n t was m u c h higher in ' B l o o d R e d ' t h a n in ' M u s a m b i ' , w h i c h is an e x p r e s s i o n o f cultivar variability. T h e t i m e o f leaf s a m p l i n g in S e p t e m b e r and D e c e m b e r did n o t change t h e K c o n t e n t appreciably.
Potassium.
TABLE 3 Potassium content (%) in the leaves of shoots bearing fruits of different percentages of
granulation Cultivar
'Musambi'
Percentage granulation 0--5 6--15 16--40 41--70 > 70
CD at 5% 'Blood Red'
CD at 5%
0--5 6--15 16--40 41--70 > 70
September
December
1973
1974
Mean
1973
1974
Mean
1.75 1.97 2.00 1.95 2.05
1.63 1.80 1.88 1.98 1.99
1.69 1.89 1.94 1.97 2.02
2.00 2.10 2.12 2.30 2.52
1.42 1.54 1.75 1.87 1.89
1.71 1.82 1.94 2.09 2.22
0.26
0.23
0.31
0.34
2.30 2.35 2.47 2.52 2.54
1.88 1.98 2.17 2.34 2.47
2.47 2.45 2.53 2.55 2.57
1.81 1.85 1.85 2.27 2.43
0.24
0.29
NS
0.33
2.09 2.17 2.32 2.43 2.51
2.14 2.15 2.19 2.41 2.50
Calcium. - - T a b l e 4 clearly s h o w s t h a t Ca in t h e leaves d e c r e a s e d significantly as t h e i n c i d e n c e o f g r a n u l a t i o n increased in t h e fruits o f b o t h cultivars. T h e d i f f e r e n c e s in Ca c o n t e n t b e t w e e n t h e leaves c o l l e c t e d f r o m n o r m a l (0--5%) a n d g r a n u l a t e d ( > 70%) f r u i t - b e a r i n g s h o o t s w e r e m o r e m a r k e d in S e p t e m b e r 1974. - - T h e c o n t e n t o f Mg slightly increased in t h e leaves as t h e g r a n u l a t i o n in t h e fruits p r o g r e s s e d (Table 5). A similar t r e n d was f o l l o w e d until t h e fruits r e a c h e d full m a t u r i t y in ' M u s a m b i ' . H o w e v e r , an i n c o n s i s t e n t t r e n d was f o l l o w e d in S e p t e m b e r f o r ' B l o o d R e d ' , w h i c h usually c o n t a i n e d m o r e Mg in the leaves than 'Musambi'.
Magnesium.
- - A perusal o f d a t a in T a b l e 6 s h o w s t h a t Zn was i n v a r i a b l y p r e s e n t in the d e f i c i e n t range, as c o m p a r e d t o t h e s t a n d a r d values given b y C h a p m a n (1968). A slight increase in t h e Zn c o n t e n t was usually o b s e r v e d in t h e leaves of s h o o t s b e a r i n g g r a n u l a t e d fruits c o m p a r e d t o n o r m a l ones. T h i s d i f f e r e n c e
Zinc.
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TABLE 4 Calcium content (%) in the leaves of shoots bearing fruits of different percentages of granulation Cultivar
'Musambi'
Percentage granulation
0-5 6--15 16--40 41--70 > 70
CD at 5% 'Blood Red'
0-5 6--15 16--40 41--70 > 70
CD a t 5 %
September
December
1973
1974
Mean
1973
1974
Mean
4.55 4.42 4.40 4.22 3.87
4.97 3.88 3.56 3.44 3.25
4.76 4.15 3.98 3.83 3.56
4.57 4.50 4.27 4.50 4.55
4.88 4.11 3.75 3.53 3.44
4.73 4.31 4.01 4.02 3.99
0.41
0.62
NS
0.68
4.57 4.45 4.45 4.35 4.28
4.54 4.43 4.03 3.56 3.44
4.65 4.62 4.45 4.25 4.20
3.75 3.70 3.56 3.56 3.44
0.38
0.52
0.42
NS
4.51 4.44 4.24 3.96 3.86
4.20 4.16 4.01 3.91 3.82
TABLE 5 Magnesium content (%) in the leaves of shoots bearing fruits of different percentages of granulation Cultivar
'Musambi'
Percentage granulation
0--5 6--15 16--40 41--70 > 70
CD at 5% 'Blood Red'
CD at 5%
0-5 6--15 16--40 41--70 > 7O
December
September 1973
1974
Mean
1973
1974
Mean
0.153 0.155 0.165 0.172 0.177
0.146 0.153 0.161 0.169 0.175
0.150 0.154 0.163 0.171 0.176
0.150 0.150 0.150 0.185 0.185
0.138 0.144 0.163 0.165 0.172
0.144 0.147 0.157 0.175 0.179
NS
0.028
0.031
0.029
0.260 0.265 0.270 0.315 0.320
0.263 0.225 0.196 0.195 0.196
0.270 0.290 0.290 0.290 0.300
0.190 0.190 0.193 0.195 0.196
0.039
0.051
NS
NS
0.262 0.245 0.233 0.255 0.258
0.230 0.240 0.242 0.243 0.248
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TABLE 6 Zinc content (rag/l) in the leaves of shoots bearing fruits of different percentages of granulation Cultivar
Percentage
December
September
granulation 'Musambi'
0--5 6--15 16--40 41--70 > 70
CD at 5% 'Blood Red'
C D at 5%
0--5 6-15 16--40 41--70 > 70
1973
1974
Mean
1973
1974
Mean
13.0 14.0 15.2 16.0 16.2
13.8 16.5 16.5 16.5 17.0
13.4 15.3 15.9 16.3 16.6
11.2 11.2 12.0 14.0 18.2
12.0 15.6 16.5 16.5 20.0
11.6 13.2 14.3 15.2 19.1
NS
NS
6.8
7.3
14.2 15.2 16.2 15.2 16.2
15.3 17.5 13.8 11.3 11.3
16.5 14.5 13.5 16.2 16.4
12.0 15.6 18.3 18.6 14.0
NS
NS
NS
NS
14.8 16.3 15.0 13.3 13.8
14.3 15.1 15.9 17.4 15.2
became significantly larger in D ecem be r in 'Musambi', while an inconsistent trend was noticed in 'Blood Red'. Copper. ~ Copper was present in the o p t i m u m range in the leaves of fruiting shoots according to the standards fixed by Chapman (1968). However, the c o n t e nts were higher in the leaves of shoots bearing granulated fruits (Table 7) than in normal ones and the difference became significantly larger in D e c e m b e r 1974 in 'Musambi', and in D e c e m b e r 1973 in 'Blood Red'.
- - A gradual decrease in Fe c o n t e n t was observed in the leaves as the degree of granulation increased in the fruits (Table 8) in bot h cultivars and m o n t h s of sampling. The values decreased significantly in the leaves of granulated fruit~ bearing shoots as com par e d with those of normal ones.
Iron.
- - An inconsistent trend was observed in Mn c o n t e n t in the leaves as the granulation progressed (Table 9). T he leaf samples collected in D e c e m b e r 1974 from granulated fruit-bearing shoots showed significant accumulation o f this element c o m p a r e d with t h a t of normal (0--5%) and partially granulated (6--15%) fruit~bearing shoots.
Manganese.
- - Th e B c o n t e n t in the leaves decreased (Table 10) as the granulation progressed in b o th 'Musambi' (non-significant) and 'Blood Red' (significant). The level o f this ele m e nt in all the classes of granulation increased in the m o n t h o f December. F u r th er m or e , 'Blood Red' contained higher values than 'Musambi'.
Boron.
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TABLE 7 Copper content (mg/1) in the leaves of shoots bearing fruits of different percentages of granulation Cultivar
'Musambi'
Percentage granulation
0--5 6--15 16--40 41--70 > 70
CD at 5% 'Blood Red'
0--5 6--15 16--40 41--70 > 70
CD at 5%
December
September 1973
1974
Mean
1973
1974
Mean
12.5 14.5 14.7 14.7 14.7
7.8 7.8 7.8 11.5 13.8
10.2 11.2 11.3 13.1 14.3
15.0 18.0 18.5 19.0 19.0
8.3 11.9 12.8 16.5 17.0
11.7 14.9 15.7 17.8 18.0
NS
NS
14.0 15.2 15.2 15.8 17.8 NS
8.8 9.0 9.1 9.2 9.2
11.4 12,1 12,2 12,5 13,5
NS
NS
7.8
13.5 20.0 20.0 22.2 23.5
7.5 7.6 7.8 8.3 8.8
8.3
10.5 13.8 13.9 15.3 16.2
NS
TABLE 8 Iron content (mg/1) in the leaves of shoots bearing fruits of different percentages of granulation Cultivar
'Musambi'
Percentage granulation
0--5 6--15 16--40 41--70 > 70
CD a t 5 % 'Blood Red'
CD a t 5 %
0--5 6--15 16--40 41--70 > 70
September
December
1973
1974
Mean
1973
1974
Mean
124 121 111 107 103
132 120 120 115 115
128 120 116 111 109
115 111 91 88 87
141 132 132 113 101
128 122 111 101 94
NS
NS
138 110 107 106 101
120 115 101 100 95
27
NS
129 113 104 103 98
NS
32
122 115 109 108 103
133 126 110 108 107
NS
NS
128 120 109 108 105
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TABLE 9 M a n g a n e s e c o n t e n t ( m g / l ) in t h e leaves o f s h o o t s bearing fruits o f d i f f e r e n t p e r c e n t a g e s of granulation
Cultivar
'Musambi'
Percentage granulation
0--5 6--15 16--40 41--70 > 70
CD a t 5% 'Blood Red'
0--5 6--15 16--40 41--70 > 70
CD at 5%
September
December
1973
1974
Mean
1973
1974
Mean
25.0 26.0 28.6 28.0 24.6
18.8 20.0 17.5 22.5 21.2
21.9 23.0 23.1 25.3 22.9
26.2 29.0 23.5 25.5 27.5
20.0 17.5 26.3 25.0 30.0
23.1 23.3 24.9 25.3 28.8
NS
NS
37.0 35.0 32.0 37.1 31.0
46,3 52.5 45,0 42.5 42,5
NS
NS
NS 41.7 43.8 38.5 39.8 36.7
9.2
36.2 38.0 36.5 38.0 36.0
46.3 46.3 45.0 45.0 48.8
NS
NS
41.3 42.2 40.8 41.5 42.4
T A B L E 10 B o r o n c o n t e n t (mg/1) in t h e leaves o f s h o o t s b e a r i n g fruits of d i f f e r e n t p e r c e n t a g e s of g r a n u l a t i o n . D a t a for 1 9 7 4 are missing d u e t o a t e c h n i c a l e r r o r
Cultivar
Percentage granulation
September 1973
December 1973
Mean
'Musambi'
0--5 6--15 16--40 41--70 > 70
158 156 153 147 147
186 184 177 173 159
172 170 165 160 153
NS
NS
205 193 191 180 173
237 230 223 217 205
29
31
CD a t 5% 'Blood Red'
CD a t 5%
0---5 6--15 16--40 41--70 > 70
221 212 207 199 189
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DISCUSSION The perusal of data has revealed that total N content in the leaves of shoots bearing granulated fruits increased as compared to non-granulated (normal) fruits in 'Musambi' and 'Blood Red', suggesting a relationship of leaf N with the granulation in citrus fruits. The lower levels of N in the leaves during 1974 as compared to the previous year may be attributed to seasonal and environmental variations (Chapman, 1968). Granulation in citrus has been directly related with the size of the fruit and the conditions which favour excessive fruit growth, i.e. high N fertilization and other factors (Bartholomew et al., 1941; Matsumoto, 1964). High N in the leaves of granulated fruit-bearing shoots in the present studies and that observed in the granulated fruits (Munshi et al., 1978a) lends support to the hypothesis that high N supply may be conducive to granulation (Matsumoto, 1964). Higher levels of P in the fruits have been shown to be associated with the development of granulation (Munshi et al., 1978a) as it affected carbohydrate metabolism (Bartholomew et al., 1941; Lloyd, 1961). It has already been well documented that granulated fruits contain higher levels of polysaccharides like starch, cellulose, pectin, etc. (Lloyd, 1961; Awasthi, 1969). The accumulation of P in the granulated fruits (Munshi et al., 1978a) and in the leaves of shoots bearing granulated fruits, observed in the present study, may have occurred as a result of its blockage in the translocation of P compounds from fruits and leaves to other parts of the tree. This has been shown in recent translocation studies conducted using radioactive sucrose (Singh, 1977). Apart from that, lower levels of P in the leaves of non-fruiting twigs have been shown to be associated with granulation in citrus fruits (Munshi et al., 1978b). These results have suggested that P from the leaves of non-fruiting shoots and shoots bearing non-granulated fruits was translocated more than sugar phosphates to other parts of the tree, as compared to shoots bearing granulated fruits. This condition has led to accumulation of this element in the granulated fruits (Munshi et al., 1978a) and leaves bearing granulated fruits as observed in the present study. Furthermore, the enzyme starch phosphorylase is known to liberate inorganic phosphate during starch synthesis (Conn and Stumpf, 1972) causing accumulation of P in the granulated fruits. High K in granulated fruits was reported by Lloyd (1961), Awasthi (1969) and Munshi et al. (1978a). Similar results in the leaves of fruiting-shoots, observed in the present study, further lend support to the conclusion that K plays a role in causing granulation. It may be added that K content in the soils of the Abohar area is quite high (unpublished data), which influenced its translocation into the tree (Mann et al., 1978), causing an increase in the size of the fruits (Embleton and Jones, 1956; Chapman, 1968) and these conditions subsequently have a direct relationship with the incidence of granulation in citrus fruits (Bartholomew et al., 1941). A recent survey of citrus orchards has revealed that granulation was aggravated significantly when K in the leaves was found in the high range (Munshi et al., 1978b).
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A decrease in Ca in the leaves, as the granulation progressed in the fruits, may be attributed to blockage of metabolites from the granulated fruits to the lower parts of the trees (Singh, 1977). Apart from that, Ca is known to be associated with the movement of sugars within the plants (Johem, 1957) which might be present in the bound form as calcium pectate in the granulated fruits and hence decrease Ca availability for downward movement. In general, Mg in the leaves remained in the low range according to the optimum values given by Embleton et al. (1963), which may be due to K--Mg antagonism (Rasmussen and Smith, 1960) as the K was quite high in the soils of this area (Mann et al., 1978). A slight increase in Mg was associated with the progress of granulation in 'Musambi'. The tendency of Zn and Cu to accumulate in the leaves of fruiting shoots supporting granulated fruits tallies with our observations in the fruits (Munshi et al., 1978a), thus supporting the contention advanced by Sinclair and Jolliffe (1961) that mineral constituents in the fruits increased with the granulation. A gradual decrease in Fe content was observed in the leaves as the degree of granulation increased in the fruits. In another study, Munshi et al. (1978a) also demonstrated a decrease in Fe content in the granulated fruit pulp, suggesting that Fe content may have been influenced by factors responsible for causing granulation in citrus. These factors could be the low level of endogenous organic chelates, high moisture and high K content in the shoots bearing granulated fruits, inhibiting the translocation of Fe in the shoot (Chapman, 1968). The Mn content in the leaves, which did not show any relationship to granulation, seemed to be of little importance. A decrease in B content in the leaves with the progress of granulation, as observed in the present study, has also been reported earlier by Awasthi (1969). However, the level of B in all the classes of granulation increased in the month of December, which may be attributed to continuous translocation of this element into the fruiting shoots. B is transported in the plants as a boron-sugar complex (Gauch and Dugger, 1953). Granulation is associated with low soluble carbohydrates in the fruits (Sinclair and Jolliffe, 1961; Lloyd, 1961), which correspondingly translocate less B into the fruits (Munshi et al., 1978a) and fruiting shoots (present investigation) bearing granulated fruits, but it is important to point out that the B in the leaves collected from non-fruiting shoots was present optimally (Mann et al., 1978) and this has been shown to be associated with granulation in sweet orange (Munshi et al., 1978b). Probably a reduced influx of a sugar--boron complex with the granulated fruit-bearing shoots has caused accumulation of B in the leaves of non-fruiting shoots and the shoots bearing non-granulated fruits. However, this concept needs to be suitably investigated before any definite conclusion can be drawn. REFERENCES Awasthi, R.P., 1969. Studies on granulation in sweet orange. Ph.D. Thesis, submitted to Punjab Agric. Univ., Ludhiana.
367
Bartholomew, E.T., Sinclair, W.B. and Turrell, F.M., 1941. Granulation of Valencia oranges. Calif. Agric. Exp. Stn. Bull., No. 647. Chapman, H.D., 1960. Leaf and soil analyses in citrus orchards. Univ. California, Div. Agric. Sci., Ext. Serv. Manual, 25, 53 pp. Chapman, H.D., 1968. The mineral nutrition of citrus. In: W. Reuther, L.D. Batchelor and H.J. Webber (Editors), Citrus Industry, Vol. II, Univ. Calif., Riverside, 127 pp. Conn, E.E. and Stumpf, P.K., 1972. Anaerobic carbohydrate metabolism. In: Outlines of Biochemistry. 3rd Edn., Wiley, New York, London, Sydney, chap. 9. Embleton, T.W. and Jones, W.W., 1956. Potash and orange fruit size. Calif. Citrogr., 41: 377-379. Embleton, T.W., Labanauskas, C.K., Jones, W.W. and Cree, C.B., 1963. Inter-relations of leaf sampling methods and nutritional status of orange trees and their influence on the macro- and micro-nutrient concentrations in orange leaves. Proc. Am. Soc. Hortic. Sci., 82: 131--141. Gauch, H.G. and Dugger, W.M., 1953. The role of boron in the translocation of sucrose. Plant Physiol., 28: 257--266. Hield, H.Z. and Erickson, L.C., 1962. Plant regulator uses of 2,4-D on citrus. Calif. Citrogr., 47: 308, 331--334. Johem, H.E., 1957. Carbohydrate distribution as affected by calcium deficiency in cotton. Plant Physiol., 32: 113--117. Lloyd, R.H., 1961. Granulation and regreening. Citrus News, 37: 21, 25. Manchanda, H.R., 1974. Chemical composition of sweet orange (Citrus sinensis Osbeck) leaves affected by foliar application of Zn, Cu, Mn and Fe alone and their combinations - - V a r . Pineapple. Indian J. Hortic., 31: 134--137. Mann, M.S., Munshi, S.K., Bajwa, M.S. and Arora, C.L., 1978. Leaf nutrient status in healthy and declining sweet orange trees in Punjab orchards. Indian J. Agric. Sci., in press. Matsumoto, K., 1964. Studies on granulation in late maturity oranges, especially the Sanbokan variety (Japanese). Mere. Ehime Univ. See VI (Agric.), 10: 585--645. Munshi, S.K., Jawanda, J.S., Singh, R. and Vii, V.K., 1978a. Studies on mineral composition of fruits in relation to severity of granulation in Dancy tangerine. Indian J. Hortic., in press. Munshi, S.K., Mann, M.S., Bajwa, M.S., Vij, V.K. and Thatai, S.K., 1978b. Physico-chemical characteristics of the fruits of healthy and declining sweet orange trees and their relation to various leaf and soil analyses values. Indian J. Hortic., in press. Munshi, S.K., Mehrotra, N.K. and Jawanda, J.S., 1978c. Use of weighted arithmetic mean for assessing granulation in citrus orchards. Indian J. Hortic., presented. Rasmussen, G.K. and Smith, P.F., 1960. Growth of pineapple orange seedlings in sand culture with various levels of K, Ca and Mg. Proc. Fla. Soil Crop Sci. Soc., 20: 183--190. Singh, R., 1977. Some studies on citrus granulation. Ph.D. Thesis, submitted to Indian Agric. Res. Inst., New Delhi. Sinclair, W.B. and Jolliffe, V.A., 1961. Chemical changes in the juice vesicles of granulated Valencia oranges. J. F o o d Sci., 26: 272--282.
357
Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
MINERAL COMPOSITION OF LEAVES IN RELATION TO DEGREE OF GRANULATION IN SWEET ORANGE
S.K. MUNSHI, R A G H B I R SINGH, V.K. VIJ and J.S.J A W A N D A
Regional Fruit Research Station, Punjab Agricultural University, A bohar 152116 (India) (First received 3 April 1978; in revised form 19 June 1978)
ABSTRACT Munshi, S.K., Singh, R., Vij, V.K. and Jawanda, J.S., 1978. Mineral composition of leaves in relation to degree of granulation in sweet orange. Scientia Hortic., 9: 357--367. Studies on the possible relationship between macro- as well as micro-elements in the leaves of fruiting-shoots and in the fruits at different degrees of granulation, were carried out in 2 cultivars of sweet orange, viz. 'Musambi' and 'Blood Red', by following a special leaf-sampling technique. The data have revealed accumulation of N, P, K, Mg, Zn and Cu, a decrease of Ca, Fe and B, and no change in Mn content in the leaves as the granulation progressed in both cultivars. Varietal variation influenced the level of N, K, Mg, Mn and B in the leaves. The metabolism of each element has been discussed in the light of various agro-climatic conditions prevailing in this area.
INTRODUCTION
The problem of granulation in fruits has assumed serious proportions in the citrus orchards of north India, particularly those in arid, irrigated tracts of Punjab. A number of workers (Lloyd, 1961; Hield and Erickson, 1962; Awasthi, 1969; Manchanda, 1974) have studied different aspects of the problem, but so far no satisfactory solution has been found. A few researchers (Sinclair and Jolliffe, 1961; Lloyd, 1961; Awasthi, 1969) have shown that granulated fruits contained excessive amounts of mineral constituents. Information on the relationship of both macro- and micro-nutrients in the granulated fruits has recently been presented by Munshi et al. (1978a). According to another study (Munshi et al., 1978b), low P and high K and B in the leaves, and soil characteristics like loamy to clay--loam texture and excess free lime, appeared to aggravate the granulation. The nutritional status in citrus has been recognised as an important tool for determining the vigour of the plants (Embleton et al., 1963; Chapman, 1968). It is felt that studies on the relationship between mineral composition of the leaves and degree of granulation in the fruits can contribute to a proper understanding of the cause(s) of this physiological disorder. The present studies were therefore attempted to reveal this relationship.
358
MATERIALS AND METHODS
Twelve~year old trees of 'Musambi' and 'Blood Red' cultivars of s~veet orange (Citrus sinensis (L.) Obseck), raised on rough lemon (Citrus j a m bhiri Lush. ),
were selected in the citrus plantations at our research station. The fruits (about 1000) were tagged in the first week of September and the leaves of corresponding branches were collected separately in small paper bags. The leaves so obtained were washed, dried and stored as detailed below. At the end of the ripeningperiod, i.e. early December in the case of 'Musambi' and the end of December for 'Blood Red', the tagged fruits were cut to assess the extent of granulation. The leaf samples collected in September were categorised and grouped according to the percentage of granulation in the fruit. Similarly, leaves were collected from the other (untagged) fruiting-shoots in December, depending on the maturity of fruits in each cultivar, and grouped according to the percentage of granulation. The leaf samples were collected in 1973 and 1974 and were grouped into 5 grades on the basis of severity of granulation of the fruits, viz. 0--5, 6--15, 16--40, 41--70 and above 70%. The assessment for the degree of granulation was carried o u t b y cutting thin sections (0.5 cm thickness) from the stem end extending perpendicularly d o w n to the stylar end. The percentage of granulation was measured b y visual inspection and calculated after Munshi et al. (1978c). There were 3 replications and critical differences (C.D.) were calculated from a randomised block design. Usually, the leaf samples collected from non-fruiting shoots are preferred over fruiting shoots for a number of reasons (Embleton et al., 1963). However, the present studies were purposely carried o u t on the leaves taken from the fruiting shoots to elucidate the nutritional imbalance, if any, occurring in the fruits/fruiting twigs with the development of granulation. Therefore, the standards fixed b y Chapman (1960) and Embleton et al. (1963) have been used for comparison. The leaves were immediately brought to the laboratory, washed, dried and ground to a powder, following the procedure of Mann et al. (1978). Total nitrogen was estimated b y a micro-Kjeldahl m e t h o d and all other elements on an emission s p e c t r o p h o t o m e t e r in the Plant Analyses Laboratory, Department of Soils, Punjab Agricultural University, Ludhiana. RESULTS
Nitrogen. - - Total N c o n t e n t in the leaves of shoots bearing from normal to
granulated fruits increased in September in both cultivars (Table 1). The leaves collected in December revealed a similar trend although the data for 1974 was found to be non-significant. Total N was also lower in the leaves during 1974 as compared to the previou~ year. Phosphorus. - - The level of P in the leaves collected from granulated (> 70%)
fruit~bearing shoots was found to be significantly higher than that of normal
359
TABLE 1 Nitrogen content (%) in the leaves of shoots bearing fruits of different percentages of granulation Cultivar
'Musambi'
Percentage granulation
0--5 6--15 16--40 41--70 > 70
CD at 5% 'Blood Red'
0--5 6--15 16--40 41--70 > 70
CD at 5%
September
December
1973
1974
Mean
1973
1974
Mean
2.62 2.71 2.71 2.68 2.72
2.27 2.30 2.30 2.38 2.41
2.45 2.51 2.51 2.53 2.57
2.71 2.71 2.80 2.85 2.89
2.21 2.23 2.30 2.33 2.34
2.46 2.47 2.55 2.59 2.62
NS
0.12
0.13
NS
2.62 2.75 2.80 2.85 2.87
2.27 2.30 2.32 2.35 2.37
2.60 2.62 2.84 2.85 2.89
2.28 2.31 2.33 2.32 2.32
0.16
NS
0.13
NS
2.45 2.53 2.56 2.60 2.62
2.44 2.47 2.59 2.59 2.61
shoots (0--5%) in 'Musambi' (December) and 'Blood Red' (September and December). The leaves collected in September and December did not show any variation in P content (Table 2). TABLE 2 Phosphorus content (%) in the leaves of shoots bearing fruits of different percentages of granulation Cultivar
'Musambi'
Percentage granulation
0--5 6--15 16--40 41--70 > 70
CD at 5% 'Blood Red'
CD at 5%
0--5 6--15 16--40 41--70 > 70
September
December
1973
1974
Mean
1973
1974
Mean
0.150 0.150 0.150 0.160 0.150
0.160 0.160 0.160 0.160 0.160
0.155 0.155 0.155 0.160 0.155
0.140 0.140 0.140 0.150 0.170
0.150 0.160 0.160 0.180 0.180
0.145 0.150 0.150 0.165 0.175
NS
NS
0.018
0.023
0.135 0.150 0.160 0.180 0.180
0.130 0.150 0.150 0.160 0.160
0.145 0.150 0.160 0.160 0.170
0.150 0.150 0.150 0.160 0.160
0.021
0.023
0.021
NS
0.133 0.150 0.155 0.170 0.170
0.148 0.150 0.155 0.160 0.165
360
- - T h e d a t a p r e s e n t e d in T a b l e 3 reveal t h a t K c o n t e n t in t h e leaves increased significantly, progressively w i t h the degree o f g r a n u l a t i o n in b o t h ' M u s a m b i ' a n d ' B l o o d R e d ' . P o t a s s i u m c o n t e n t was m u c h higher in ' B l o o d R e d ' t h a n in ' M u s a m b i ' , w h i c h is an e x p r e s s i o n o f cultivar variability. T h e t i m e o f leaf s a m p l i n g in S e p t e m b e r and D e c e m b e r did n o t change t h e K c o n t e n t appreciably.
Potassium.
TABLE 3 Potassium content (%) in the leaves of shoots bearing fruits of different percentages of
granulation Cultivar
'Musambi'
Percentage granulation 0--5 6--15 16--40 41--70 > 70
CD at 5% 'Blood Red'
CD at 5%
0--5 6--15 16--40 41--70 > 70
September
December
1973
1974
Mean
1973
1974
Mean
1.75 1.97 2.00 1.95 2.05
1.63 1.80 1.88 1.98 1.99
1.69 1.89 1.94 1.97 2.02
2.00 2.10 2.12 2.30 2.52
1.42 1.54 1.75 1.87 1.89
1.71 1.82 1.94 2.09 2.22
0.26
0.23
0.31
0.34
2.30 2.35 2.47 2.52 2.54
1.88 1.98 2.17 2.34 2.47
2.47 2.45 2.53 2.55 2.57
1.81 1.85 1.85 2.27 2.43
0.24
0.29
NS
0.33
2.09 2.17 2.32 2.43 2.51
2.14 2.15 2.19 2.41 2.50
Calcium. - - T a b l e 4 clearly s h o w s t h a t Ca in t h e leaves d e c r e a s e d significantly as t h e i n c i d e n c e o f g r a n u l a t i o n increased in t h e fruits o f b o t h cultivars. T h e d i f f e r e n c e s in Ca c o n t e n t b e t w e e n t h e leaves c o l l e c t e d f r o m n o r m a l (0--5%) a n d g r a n u l a t e d ( > 70%) f r u i t - b e a r i n g s h o o t s w e r e m o r e m a r k e d in S e p t e m b e r 1974. - - T h e c o n t e n t o f Mg slightly increased in t h e leaves as t h e g r a n u l a t i o n in t h e fruits p r o g r e s s e d (Table 5). A similar t r e n d was f o l l o w e d until t h e fruits r e a c h e d full m a t u r i t y in ' M u s a m b i ' . H o w e v e r , an i n c o n s i s t e n t t r e n d was f o l l o w e d in S e p t e m b e r f o r ' B l o o d R e d ' , w h i c h usually c o n t a i n e d m o r e Mg in the leaves than 'Musambi'.
Magnesium.
- - A perusal o f d a t a in T a b l e 6 s h o w s t h a t Zn was i n v a r i a b l y p r e s e n t in the d e f i c i e n t range, as c o m p a r e d t o t h e s t a n d a r d values given b y C h a p m a n (1968). A slight increase in t h e Zn c o n t e n t was usually o b s e r v e d in t h e leaves of s h o o t s b e a r i n g g r a n u l a t e d fruits c o m p a r e d t o n o r m a l ones. T h i s d i f f e r e n c e
Zinc.
361
TABLE 4 Calcium content (%) in the leaves of shoots bearing fruits of different percentages of granulation Cultivar
'Musambi'
Percentage granulation
0-5 6--15 16--40 41--70 > 70
CD at 5% 'Blood Red'
0-5 6--15 16--40 41--70 > 70
CD a t 5 %
September
December
1973
1974
Mean
1973
1974
Mean
4.55 4.42 4.40 4.22 3.87
4.97 3.88 3.56 3.44 3.25
4.76 4.15 3.98 3.83 3.56
4.57 4.50 4.27 4.50 4.55
4.88 4.11 3.75 3.53 3.44
4.73 4.31 4.01 4.02 3.99
0.41
0.62
NS
0.68
4.57 4.45 4.45 4.35 4.28
4.54 4.43 4.03 3.56 3.44
4.65 4.62 4.45 4.25 4.20
3.75 3.70 3.56 3.56 3.44
0.38
0.52
0.42
NS
4.51 4.44 4.24 3.96 3.86
4.20 4.16 4.01 3.91 3.82
TABLE 5 Magnesium content (%) in the leaves of shoots bearing fruits of different percentages of granulation Cultivar
'Musambi'
Percentage granulation
0--5 6--15 16--40 41--70 > 70
CD at 5% 'Blood Red'
CD at 5%
0-5 6--15 16--40 41--70 > 7O
December
September 1973
1974
Mean
1973
1974
Mean
0.153 0.155 0.165 0.172 0.177
0.146 0.153 0.161 0.169 0.175
0.150 0.154 0.163 0.171 0.176
0.150 0.150 0.150 0.185 0.185
0.138 0.144 0.163 0.165 0.172
0.144 0.147 0.157 0.175 0.179
NS
0.028
0.031
0.029
0.260 0.265 0.270 0.315 0.320
0.263 0.225 0.196 0.195 0.196
0.270 0.290 0.290 0.290 0.300
0.190 0.190 0.193 0.195 0.196
0.039
0.051
NS
NS
0.262 0.245 0.233 0.255 0.258
0.230 0.240 0.242 0.243 0.248
362
TABLE 6 Zinc content (rag/l) in the leaves of shoots bearing fruits of different percentages of granulation Cultivar
Percentage
December
September
granulation 'Musambi'
0--5 6--15 16--40 41--70 > 70
CD at 5% 'Blood Red'
C D at 5%
0--5 6-15 16--40 41--70 > 70
1973
1974
Mean
1973
1974
Mean
13.0 14.0 15.2 16.0 16.2
13.8 16.5 16.5 16.5 17.0
13.4 15.3 15.9 16.3 16.6
11.2 11.2 12.0 14.0 18.2
12.0 15.6 16.5 16.5 20.0
11.6 13.2 14.3 15.2 19.1
NS
NS
6.8
7.3
14.2 15.2 16.2 15.2 16.2
15.3 17.5 13.8 11.3 11.3
16.5 14.5 13.5 16.2 16.4
12.0 15.6 18.3 18.6 14.0
NS
NS
NS
NS
14.8 16.3 15.0 13.3 13.8
14.3 15.1 15.9 17.4 15.2
became significantly larger in D ecem be r in 'Musambi', while an inconsistent trend was noticed in 'Blood Red'. Copper. ~ Copper was present in the o p t i m u m range in the leaves of fruiting shoots according to the standards fixed by Chapman (1968). However, the c o n t e nts were higher in the leaves of shoots bearing granulated fruits (Table 7) than in normal ones and the difference became significantly larger in D e c e m b e r 1974 in 'Musambi', and in D e c e m b e r 1973 in 'Blood Red'.
- - A gradual decrease in Fe c o n t e n t was observed in the leaves as the degree of granulation increased in the fruits (Table 8) in bot h cultivars and m o n t h s of sampling. The values decreased significantly in the leaves of granulated fruit~ bearing shoots as com par e d with those of normal ones.
Iron.
- - An inconsistent trend was observed in Mn c o n t e n t in the leaves as the granulation progressed (Table 9). T he leaf samples collected in D e c e m b e r 1974 from granulated fruit-bearing shoots showed significant accumulation o f this element c o m p a r e d with t h a t of normal (0--5%) and partially granulated (6--15%) fruit~bearing shoots.
Manganese.
- - Th e B c o n t e n t in the leaves decreased (Table 10) as the granulation progressed in b o th 'Musambi' (non-significant) and 'Blood Red' (significant). The level o f this ele m e nt in all the classes of granulation increased in the m o n t h o f December. F u r th er m or e , 'Blood Red' contained higher values than 'Musambi'.
Boron.
363
TABLE 7 Copper content (mg/1) in the leaves of shoots bearing fruits of different percentages of granulation Cultivar
'Musambi'
Percentage granulation
0--5 6--15 16--40 41--70 > 70
CD at 5% 'Blood Red'
0--5 6--15 16--40 41--70 > 70
CD at 5%
December
September 1973
1974
Mean
1973
1974
Mean
12.5 14.5 14.7 14.7 14.7
7.8 7.8 7.8 11.5 13.8
10.2 11.2 11.3 13.1 14.3
15.0 18.0 18.5 19.0 19.0
8.3 11.9 12.8 16.5 17.0
11.7 14.9 15.7 17.8 18.0
NS
NS
14.0 15.2 15.2 15.8 17.8 NS
8.8 9.0 9.1 9.2 9.2
11.4 12,1 12,2 12,5 13,5
NS
NS
7.8
13.5 20.0 20.0 22.2 23.5
7.5 7.6 7.8 8.3 8.8
8.3
10.5 13.8 13.9 15.3 16.2
NS
TABLE 8 Iron content (mg/1) in the leaves of shoots bearing fruits of different percentages of granulation Cultivar
'Musambi'
Percentage granulation
0--5 6--15 16--40 41--70 > 70
CD a t 5 % 'Blood Red'
CD a t 5 %
0--5 6--15 16--40 41--70 > 70
September
December
1973
1974
Mean
1973
1974
Mean
124 121 111 107 103
132 120 120 115 115
128 120 116 111 109
115 111 91 88 87
141 132 132 113 101
128 122 111 101 94
NS
NS
138 110 107 106 101
120 115 101 100 95
27
NS
129 113 104 103 98
NS
32
122 115 109 108 103
133 126 110 108 107
NS
NS
128 120 109 108 105
364
TABLE 9 M a n g a n e s e c o n t e n t ( m g / l ) in t h e leaves o f s h o o t s bearing fruits o f d i f f e r e n t p e r c e n t a g e s of granulation
Cultivar
'Musambi'
Percentage granulation
0--5 6--15 16--40 41--70 > 70
CD a t 5% 'Blood Red'
0--5 6--15 16--40 41--70 > 70
CD at 5%
September
December
1973
1974
Mean
1973
1974
Mean
25.0 26.0 28.6 28.0 24.6
18.8 20.0 17.5 22.5 21.2
21.9 23.0 23.1 25.3 22.9
26.2 29.0 23.5 25.5 27.5
20.0 17.5 26.3 25.0 30.0
23.1 23.3 24.9 25.3 28.8
NS
NS
37.0 35.0 32.0 37.1 31.0
46,3 52.5 45,0 42.5 42,5
NS
NS
NS 41.7 43.8 38.5 39.8 36.7
9.2
36.2 38.0 36.5 38.0 36.0
46.3 46.3 45.0 45.0 48.8
NS
NS
41.3 42.2 40.8 41.5 42.4
T A B L E 10 B o r o n c o n t e n t (mg/1) in t h e leaves o f s h o o t s b e a r i n g fruits of d i f f e r e n t p e r c e n t a g e s of g r a n u l a t i o n . D a t a for 1 9 7 4 are missing d u e t o a t e c h n i c a l e r r o r
Cultivar
Percentage granulation
September 1973
December 1973
Mean
'Musambi'
0--5 6--15 16--40 41--70 > 70
158 156 153 147 147
186 184 177 173 159
172 170 165 160 153
NS
NS
205 193 191 180 173
237 230 223 217 205
29
31
CD a t 5% 'Blood Red'
CD a t 5%
0---5 6--15 16--40 41--70 > 70
221 212 207 199 189
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DISCUSSION The perusal of data has revealed that total N content in the leaves of shoots bearing granulated fruits increased as compared to non-granulated (normal) fruits in 'Musambi' and 'Blood Red', suggesting a relationship of leaf N with the granulation in citrus fruits. The lower levels of N in the leaves during 1974 as compared to the previous year may be attributed to seasonal and environmental variations (Chapman, 1968). Granulation in citrus has been directly related with the size of the fruit and the conditions which favour excessive fruit growth, i.e. high N fertilization and other factors (Bartholomew et al., 1941; Matsumoto, 1964). High N in the leaves of granulated fruit-bearing shoots in the present studies and that observed in the granulated fruits (Munshi et al., 1978a) lends support to the hypothesis that high N supply may be conducive to granulation (Matsumoto, 1964). Higher levels of P in the fruits have been shown to be associated with the development of granulation (Munshi et al., 1978a) as it affected carbohydrate metabolism (Bartholomew et al., 1941; Lloyd, 1961). It has already been well documented that granulated fruits contain higher levels of polysaccharides like starch, cellulose, pectin, etc. (Lloyd, 1961; Awasthi, 1969). The accumulation of P in the granulated fruits (Munshi et al., 1978a) and in the leaves of shoots bearing granulated fruits, observed in the present study, may have occurred as a result of its blockage in the translocation of P compounds from fruits and leaves to other parts of the tree. This has been shown in recent translocation studies conducted using radioactive sucrose (Singh, 1977). Apart from that, lower levels of P in the leaves of non-fruiting twigs have been shown to be associated with granulation in citrus fruits (Munshi et al., 1978b). These results have suggested that P from the leaves of non-fruiting shoots and shoots bearing non-granulated fruits was translocated more than sugar phosphates to other parts of the tree, as compared to shoots bearing granulated fruits. This condition has led to accumulation of this element in the granulated fruits (Munshi et al., 1978a) and leaves bearing granulated fruits as observed in the present study. Furthermore, the enzyme starch phosphorylase is known to liberate inorganic phosphate during starch synthesis (Conn and Stumpf, 1972) causing accumulation of P in the granulated fruits. High K in granulated fruits was reported by Lloyd (1961), Awasthi (1969) and Munshi et al. (1978a). Similar results in the leaves of fruiting-shoots, observed in the present study, further lend support to the conclusion that K plays a role in causing granulation. It may be added that K content in the soils of the Abohar area is quite high (unpublished data), which influenced its translocation into the tree (Mann et al., 1978), causing an increase in the size of the fruits (Embleton and Jones, 1956; Chapman, 1968) and these conditions subsequently have a direct relationship with the incidence of granulation in citrus fruits (Bartholomew et al., 1941). A recent survey of citrus orchards has revealed that granulation was aggravated significantly when K in the leaves was found in the high range (Munshi et al., 1978b).
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A decrease in Ca in the leaves, as the granulation progressed in the fruits, may be attributed to blockage of metabolites from the granulated fruits to the lower parts of the trees (Singh, 1977). Apart from that, Ca is known to be associated with the movement of sugars within the plants (Johem, 1957) which might be present in the bound form as calcium pectate in the granulated fruits and hence decrease Ca availability for downward movement. In general, Mg in the leaves remained in the low range according to the optimum values given by Embleton et al. (1963), which may be due to K--Mg antagonism (Rasmussen and Smith, 1960) as the K was quite high in the soils of this area (Mann et al., 1978). A slight increase in Mg was associated with the progress of granulation in 'Musambi'. The tendency of Zn and Cu to accumulate in the leaves of fruiting shoots supporting granulated fruits tallies with our observations in the fruits (Munshi et al., 1978a), thus supporting the contention advanced by Sinclair and Jolliffe (1961) that mineral constituents in the fruits increased with the granulation. A gradual decrease in Fe content was observed in the leaves as the degree of granulation increased in the fruits. In another study, Munshi et al. (1978a) also demonstrated a decrease in Fe content in the granulated fruit pulp, suggesting that Fe content may have been influenced by factors responsible for causing granulation in citrus. These factors could be the low level of endogenous organic chelates, high moisture and high K content in the shoots bearing granulated fruits, inhibiting the translocation of Fe in the shoot (Chapman, 1968). The Mn content in the leaves, which did not show any relationship to granulation, seemed to be of little importance. A decrease in B content in the leaves with the progress of granulation, as observed in the present study, has also been reported earlier by Awasthi (1969). However, the level of B in all the classes of granulation increased in the month of December, which may be attributed to continuous translocation of this element into the fruiting shoots. B is transported in the plants as a boron-sugar complex (Gauch and Dugger, 1953). Granulation is associated with low soluble carbohydrates in the fruits (Sinclair and Jolliffe, 1961; Lloyd, 1961), which correspondingly translocate less B into the fruits (Munshi et al., 1978a) and fruiting shoots (present investigation) bearing granulated fruits, but it is important to point out that the B in the leaves collected from non-fruiting shoots was present optimally (Mann et al., 1978) and this has been shown to be associated with granulation in sweet orange (Munshi et al., 1978b). Probably a reduced influx of a sugar--boron complex with the granulated fruit-bearing shoots has caused accumulation of B in the leaves of non-fruiting shoots and the shoots bearing non-granulated fruits. However, this concept needs to be suitably investigated before any definite conclusion can be drawn. REFERENCES Awasthi, R.P., 1969. Studies on granulation in sweet orange. Ph.D. Thesis, submitted to Punjab Agric. Univ., Ludhiana.
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Bartholomew, E.T., Sinclair, W.B. and Turrell, F.M., 1941. Granulation of Valencia oranges. Calif. Agric. Exp. Stn. Bull., No. 647. Chapman, H.D., 1960. Leaf and soil analyses in citrus orchards. Univ. California, Div. Agric. Sci., Ext. Serv. Manual, 25, 53 pp. Chapman, H.D., 1968. The mineral nutrition of citrus. In: W. Reuther, L.D. Batchelor and H.J. Webber (Editors), Citrus Industry, Vol. II, Univ. Calif., Riverside, 127 pp. Conn, E.E. and Stumpf, P.K., 1972. Anaerobic carbohydrate metabolism. In: Outlines of Biochemistry. 3rd Edn., Wiley, New York, London, Sydney, chap. 9. Embleton, T.W. and Jones, W.W., 1956. Potash and orange fruit size. Calif. Citrogr., 41: 377-379. Embleton, T.W., Labanauskas, C.K., Jones, W.W. and Cree, C.B., 1963. Inter-relations of leaf sampling methods and nutritional status of orange trees and their influence on the macro- and micro-nutrient concentrations in orange leaves. Proc. Am. Soc. Hortic. Sci., 82: 131--141. Gauch, H.G. and Dugger, W.M., 1953. The role of boron in the translocation of sucrose. Plant Physiol., 28: 257--266. Hield, H.Z. and Erickson, L.C., 1962. Plant regulator uses of 2,4-D on citrus. Calif. Citrogr., 47: 308, 331--334. Johem, H.E., 1957. Carbohydrate distribution as affected by calcium deficiency in cotton. Plant Physiol., 32: 113--117. Lloyd, R.H., 1961. Granulation and regreening. Citrus News, 37: 21, 25. Manchanda, H.R., 1974. Chemical composition of sweet orange (Citrus sinensis Osbeck) leaves affected by foliar application of Zn, Cu, Mn and Fe alone and their combinations - - V a r . Pineapple. Indian J. Hortic., 31: 134--137. Mann, M.S., Munshi, S.K., Bajwa, M.S. and Arora, C.L., 1978. Leaf nutrient status in healthy and declining sweet orange trees in Punjab orchards. Indian J. Agric. Sci., in press. Matsumoto, K., 1964. Studies on granulation in late maturity oranges, especially the Sanbokan variety (Japanese). Mere. Ehime Univ. See VI (Agric.), 10: 585--645. Munshi, S.K., Jawanda, J.S., Singh, R. and Vii, V.K., 1978a. Studies on mineral composition of fruits in relation to severity of granulation in Dancy tangerine. Indian J. Hortic., in press. Munshi, S.K., Mann, M.S., Bajwa, M.S., Vij, V.K. and Thatai, S.K., 1978b. Physico-chemical characteristics of the fruits of healthy and declining sweet orange trees and their relation to various leaf and soil analyses values. Indian J. Hortic., in press. Munshi, S.K., Mehrotra, N.K. and Jawanda, J.S., 1978c. Use of weighted arithmetic mean for assessing granulation in citrus orchards. Indian J. Hortic., presented. Rasmussen, G.K. and Smith, P.F., 1960. Growth of pineapple orange seedlings in sand culture with various levels of K, Ca and Mg. Proc. Fla. Soil Crop Sci. Soc., 20: 183--190. Singh, R., 1977. Some studies on citrus granulation. Ph.D. Thesis, submitted to Indian Agric. Res. Inst., New Delhi. Sinclair, W.B. and Jolliffe, V.A., 1961. Chemical changes in the juice vesicles of granulated Valencia oranges. J. F o o d Sci., 26: 272--282.