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Effects of night-time humidity and nutrient solution concentration on the calcium content of tomato fruit
Scientia Horticulturae, 22 (1984) 207--217
207
Elsevier Science Publishers B.V., Amsterdam - - P r i n t e d in The Netherlands
EFFECTS OF NIGHT-TIME HUMIDITY AND NUTRIENT SOLUTION CONCENTRATION ON THE CALCIUM CONTENT OF TOMATO FRUIT
E.G. B R A D F I E L D and C.G. G U T T R I D G E
Long Ashton Research Station, University of Bristol, Bristol (Gt. Britain) (Accepted for publication 13 July 1983)
ABSTRACT Bradfield, E.G. and Guttridge, C.G., 1984. Effects of night-time humidity and nutrient solution concentration on the calcium content of tomato fruit. Scientia Hortic., 22: 207--217. Calcium intake into tomato fruits was greater when nights were humid rather than dry and nutrient solutions dilute rather than concentrated. The concentration of calcium in the wall tissue o f the distal segment of fruits damaged by blossom-end rot was 0.03% of dry matter, but was 2- to 3-fold greater in the most favourable conditions of humidity and solution concentration, when fruits were undamaged. Adding extra calcium to the nutrient solution increased the calcium concentration in the proximal, but not in the middle or distal,segments of the fruit. The results support the hypothesis that a positive root pressure at night promotes transport of calcium into tissuesand organs that have restrictedtranspiration. Keywords: blossom-end rot; calcium; humidity; nutrient strength; tomato. ABBREVIATION B E R ~= blossom-end rot.
INTRODUCTION
Physiological disorders of plants caused by localised shortages of calcium occur in tissues that cannot readily transpire, and result from poor distribution of calcium rather than an overall deficiency in the plant. Environmental conditions that favour the development of positive root pressure at night promote calcium transport into the enclosed vegetative tissue of cabbage (Palzkill et al., 1976; Wiebe et al., 1977) and strawberry (Bradfield and Guttridge, 1979; Guttridge et al., 1981). Fruits, particularly in their later stages of development, have low transpiration rates and some show calcium-related disorders. Palzkill and Tibbitts (1977) suggested that adequate transport of calcium into fruits may depend, as it does for
0304-4238/84/$03.00
© 1984 Elsevier Science Publishers B.V.
208
some enclosed vegetative tissues, on root pressure flow. Although there seems to be little direct experimental evidence for fruits, Robbins (1937) found that very concentrated nutrient solutions, which would be expected to reduce root pressure, decreased guttation from leaves and increased the incidence of blossom-end rot (BER) in tomatoes. Blossom-end rot of tomatoes has been associated with a calcium concentration in the whole fruit of less than 0.2% dry weight (Raleigh and Chucka, 1944; Taylor and Smith, 1957), although Ward (1973) suggested that this value may be inaccurate. Later investigators determined calcium concentrations in the distal ends of fruits where the s y m p t o m s appear. Some report calcium concentrations in the distal end of 0.02--0.05% and > 0.07% in BER and normal fruit, respectively (Gerard and Hipp, 1968; van Goor, 1968; Ward, 1973; Cerda et al., 1979), whereas others found no relationship (Millikan et al., 1971; Shaykewich et al., 1971; Pill and Lambeth, 1980). Calcium concentration gradients in fruits and changes in concentration with growth make the choice of sample tissue critical (Turner et al., 1977; Bradfield and Guttridge, 1979). The experiments reported here were done to see whether the calcium c o n t e n t and concentration in tomato fruits was affected by humidity and nutrient concentrations, factors which are known to affect root pressure. MATERIALS AND METHODS 1. - - Tomato seedlings cultivar 'Ailsa Craig' were raised in sand culture and fed with nutrient solution A (Table I) diluted 4-fold. At the 4 full-leaf stage, 2 plants were transferred to each of 12 troughs (Bradfield and Guttridge, 1979) and suspended with their roots in nutrient solution A. Six troughs were placed in each of two growth rooms with a 16 h day and temperatures of 22 -+ 1.5°C by day and 18 + 1.0°C by night. Lighting was provided in this and subsequent experiments by warm white fluorescent lamps and tungsten filament lamps, in a rated wattage ratio of 15:1,
Experiment
TABLEI C o m p o s i t i o n and o s m o t i c potential (OP, kPa) of n u t r i e n t solutions (m equiv. 1 - ' ) . All solutions contained (p.p.m.): Fe, 5; Cu, 0.064; Mn, 0.55; B, 0.33; Zn, 0.065; Mo, 0.019 Ion
A
Ca 2+ I~ Mg 2+ Na ÷ NO~ H2PO ~ C1SO~ -
6 5 5 1.33 12.5 1.33 0.5 3
OP
--52
B 29 24 24 6.4 60 6.4 2.5 14.5 --254
C 13 5 5 1.33 12.5 1.33 1.5 9 --67
D 24 20 20 5.33 50 5.33 2 12 --208
209 at PAR levels between 270 and 330 pE m -2 s -1. After 7 days, the humidity of the rooms was changed to that of the experimental treatments, dry d a y / d r y night and dry d a y / h u m i d night, water vapour pressure deficits being 760 + 110 Pa and 260 + 110 Pa for dry and humid nights, respectively, and 1000 + 170 Pa for dry days, corresponding to mean relative humidities of 64 and 87% for nights and 61% for days, respectively. (Vapour p:ressure deficits and relative humidities were calculated from psychomet:cic measurements.) After a further 7 days, when the first truss commenced to flower, the nutrient solution in 3 troughs in each room was changed to Solution B (Table I}, the extra nutrient being added over a period of 4 days to avoid salt-induced wilting. Thus, there were 6 plants in each of the 4 treatments, humid or dry nights combined with dilute (A) or .concentrated (B) nutrient solutions. Solutions were replaced weekly t h r o u g h o u t the experiment. The plants grew normally and had set 6--7 trusses by the end of the experiment. Flowers were hand-pollinated daily. Dates of flowering and fruit set were recorded individually for all fruiting positions on the first two trusses on each plant. Eight fruits were harvested at each of 5 sizes -- 23, 26, 34, 41 and 51 m m diameter -- in each treatment, 4 from the first and 4 from the second trusses. The fruits were selected according to a pattern that gave equal representation of size categories to fruiting positions on the truss between 2 and 5 inclusive, the first fvaiting position n o t being harvested. These harvesting patterns were applied to trusses randomly. In all, 160 fruits were harvested and analysed individually. The fresh weight of each sampled fruit was recorded. The distal quarter was then severed and its jelly and seeds removed from the wall tissue and bulked with the remainder of the fruit. The calcium contents of the distal end wall tissue (including the skin) and of the remainder of the fruit were determiined separately. From these data, the calcium content and concentration of the distal wall tissue and of the whole fruit were calculated. The incidence of BER was recorded 2 4 and again 38 days after the first fruit truss had set. 2 . - - 'Ailsa Craig' plants were raised in sand and transferred to troughs containing solution A. Two troughs, each containing 3 plants, were transferred at the start of flowering of the first truss to each of three controlled-environment cabinets with a 16 h day. Mean dry bulb temperatures were 20 + 0.5°C during the day and 16 + 0.5°C at night. Water vapour pressure deficits were 400 + 60 Pa by day and ~ 100 Pa at night, corresponding to mean relative humidities of 83% by day and > 95% at night. The plants were stopped 2 or 3 leaves above the second truss. After 14 days, t:ae nutrient solution in one trough in each cabinet was changed to Solution C (Table I) and subsequently both solutions were replaced weekly. Humidities in the cabinets were then changed, where necessary, gradually over a period of 3 days to the 3 experimental treatments, dry d a y / d r y
Experiment
210 night, dry d a y / h u m i d night and humid d a y / h u m i d night, water vapour pressure deficits being 400 + 60 Pa for dry and < 100 Pa for humid conditions, corresponding to mean relative humidities of 83 and 78% for dry days and nights, respectively, and > 95% for humid days or nights. Two ripening fruits were harvested from each truss on each plant in each treatment, weighed and the calcium concentration determined in the proximal, middle and distal thirds of the fruit. 3. - - Tomato plants 'Eurocross BB' were raised in sand culture as before. At the 2 full-leaf stage, 6 plants were transferred to each of 4 troughs containing nutrient solution A (Table I) in a controlled-envir o n m e n t room at 22 + 1.5°C by day and 16 + I°C by night, and a daylength of 16 h. Water vapour pressure deficits were 920 + 170 Pa (65% RH) by day and 140 + 100 Pa (93% RH} at night. Flowers were handpollinated. Plants were stopped 2 leaves above the second truss and the experimental nutrient treatments then applied. One trough remained with dilute solution {A), another contained concentrated solution (D). The remaining two troughs contained either concentrated by day, dilute at night, or dilute by day, concentrated at night. There regimes were obtained by the pumping arrangements previously described for strawberry (Guttridge et al., 1981). The concentrated solution was built up in the first place by adding 4 daily increments. Solutions were changed every 3 days. Fruits were harvested as they ripened, and the calcium concentration determined in the wall tissues of the distal quarter of the fruit. Experiment
methods. - - Fruit samples were dried at 105°C, then ashed at 450°C. The residue was treated with 16 M nitric acid, dried and ashed again. The resulting white residue was dissolved in 0.5 M hydrochloric acid and made to volume. A portion was diluted with lanthanum chloride to give a concentration of 0.07 M La, and calcium was determined by atomic absorption spectroscopy at 4227 nm in an air--acetylene flame.
Analytical
treatment o f d a t a . - - Because the environmental treatments were n o t replicated, the between-plant variation within treatments was used as a measure of error to assess the significance of humidity and nutrient salt concentration.
Statistical
RESULT 1. - - In this experiment, we investigated the effects of nighttime humidity and of nutrient concentration on the calcium c o n t e n t of t o m a t o fruits at different stages of growth and on the calcium concentration in the wall tissue of the distal quarter of the fruit in relation to the incidence of blossom-end rot. The rate of intake of calcium into the fruits may be assessed against
Experiment
211
either increase in fruit weight or number of days from fruit set. Because fruits cannot be weighed before picking, we harvested at pre-defined fruit diameters. Although individual fruits varied slightly in shape, weights of fruits at a given harvest-diameter were not significantly different between treatments. Fruits grew significantly faster in dry nights combined with dilute nutrients (Fig. la), but differences were not great. Total calcium 50
40
LSD I
3O
I,Z
20
lO Ca)
0
--
'::)
~
'
115
'
2t5
!
315 | Days to pick
t 45
3600
LS 2800
. •2000 ¢0 1200
(b)
400 O
m
!
!
Days to pick
Fig. 1. (a) F r e s h weights o f t o m a t o fruits h a r v e s t e d at p r e d e t e r m i n e d d i a m e t e r s in Exp e r i m e n t 1, p l o t t e d against days f r o m f r u i t set t o harvest. Key t o t r e a t m e n t s : t = d r y n i g h t , ,dilute s o l u t i o n ; o ffi d r y n i g h t , c o n c e n t r a t e d s o l u t i o n ; • = h u m i d n i g h t , d i l u t e s o l u t i o n ; a = h u m i d night, c o n c e n t r a t e d s o l u t i o n . (b) As (a) b u t for c a l c i u m c o n t e n t s per fruit.
212
content of fruits increased most rapidly in humid nights combined with dilute solutions, and least rapidly in the opposite combination of dry nights and concentrated solutions (Fig. lb). Thus, Ca intake per day was decreased by dry nights and by concentrated solutions. The calcium concentration in the whole fruit (Fig. 2a) and in the distal segment (Fig. 2b) was already significantly different between some treatments at the first harvest (23 mm 10"0 '
8"0
6"0
u. o
4.0 ¸
8
o~ E
I
LSD
2.0
(a) i
~5
i
i
2s
i
3'5
i 45
i
Days to pick
0"11
LSD 0'09
0'07
.~" o . o s
0"03
O-Ol 0
(b) 0
I 5
i
1~5
I
;Z5
I
I I 35 Days to pick
415
Fig. 2. (a) A s F i g . l ( a ) b u t f o r c a l c i u m c o n c e n t r a t i o n s in f r u i t as m g p e r 1 0 0 g f r e s h weight. (b) As Fig. l ( a ) but for calcium percentage of dry matter in the distal quarter
of fruits.
213 d i a m e t e r ) . Calcium intake was greatest b o t h per d a y and per u n i t fruit weight in h u m i d nights and d i l u t e solutions, and least in d r y nights and c o n c e n ~ r a t e d solutions. In the later harvests, t h e overall d i f f e r e n c e s b e t w e e n e x t r e m e t r e a t m e n t s in calcium c o n c e n t r a t i o n in t h e distal s e g m e n t were m o r e t h a n 3-fold. Over t h e 5 successive harvests, t h e average effects o f b o t h night-time h u m i d i t y and n u t r i e n t strength were highly significant b o t h for calcium c o n t e n t per f r u i t and for c o n c e n t r a t i o n (Table II). T h e first and s e c o n d truss d i f f e r e d o n l y in days t o picking; the s e c o n d truss growing m o r e rapidly. D r y nights and c o n c e n t r a t e d solutions gave greatest n u m b e r s o f fruits with B E R (Table III). Nearly all t h e fruits t h a t were t o b e c o m e so were d a m a g e d b y the first r e c o r d i n g date. N o B E R o c c u r r e d in fruits on trusses 3 and 4. Because B E R d e v e l o p e d distally and early in f r u i t o n t o g e n y , mainly b e f o r e the s e c o n d harvest size (26 m m diameter}, calcium c o n c e n t r a t i o n s TABLE :[I Significance of variance ratios (F) for treatments in Experiment 1 Fruit parameter
Variable
pick
Fresh wt. (g)
Total Ca #g/100 g % dm #g/fruit F.W. (distal)
NS * ***
* NS NS
*** *** NS
Days
Night-time h u m i d i t y Nutrient c o n c e n t r a t i o n Truss
to
Concentration Ca
*** *** NS
*** *** NS
= not significant; *,***, respresenting significance at P = 0.05 and 0.001, respectively.
NS
TABLE III Number of fruits per plant showing external blossom-end rot on the first two trusses, recorded 24 and 38 days after the fruits had set (Experiment 1) Night-time h u m i d i t y Dry
Humid
Nutrient strength
Nutrient strength
Dilute
Concentrated
Dilute
Concentrated
Days
to recording Days to recording Days to recording Days to recording
24
38
24
38
24
38
24
38
]..7 (I.7
1.7 0.7
2.0 3.0
2.3 3.0
0.5 0
0.5 0
0 0
0 0
Total 2.4
2.4
5.0
5.3
0.5
0.5
0
0
Truss 1 2
214
only in the distal wall tissue and only at the first and second harvests are relevant to its incidence. At the first t w o harvests, the greatest and second greatest incidence of BER were associated with the lowest and second lowest concentrations of distal calcium in fruits from the dry--concentrated and dry--dilute treatments, respectively (Table III and Fig. 2b). Night-time humidity was apparently more important for BER than solution strength during the early, critical growth period in this experiment. Over all treatments, the mean concentrations of calcium in the distal wall tissue of fruits with BER was 0.031% of dry matter. 2. - - This experiment studied the effect of night- and daytime humidities and of a moderate increase in nutrient calcium, with chloride and sulphate anions (solution C compared with A), on calcium concentration in the proximal, middle and distal thirds of ripening tomato fruit 'Ailsa Craig' (Table IV). Calcium concentration was always much greater in the proximal end of the fruit than in the middle and distal portions. Increasing the amount of calcium in the nutrient solution increased the calcium concentration only in the proximal third.
Experiment
TABLE IV Effects of day- and night-time relative humidity and o f the concentration of calcium in the nutrient solution on the calcium concentration (% of dry matter) in the proximal, middle and distal thirds of ripe tomato fruits of the cultivar 'Ailsa Craig' (means of 12 fruits per treatment) Treatments Ca conc. (re.equiv.
% Ca Proximal
Middle
Distal
Dry/dry Dry/humid Humid/humid
0.107 0.172 0.206
0.047 0.068 0.116
0.038 0.072 0.112
Dry/dry Dry/humid Humid/humid
0.175 0.202 0.221
0.068 0.072 0.123
0.063 0.070 0.120
0.058
0.044
0.045
* * **
NS ** *
NS ** **
Day/night humidity
1-1)
13
LSD (P ffi 0.05) Significance of variance ratios (F) for the following: Ca in nutrient solution Day humidity Night humidity
NS = not significant; *, **, representing significance at P = 0.05 and 0.01, respectively.
215
Humid nights and humid days increased fruit calcium concentration significantly in all fruit segments, but it should be noted that night humidity comparisons were tested only following dry days, and day effects tested only following humid nights. The greatest increases in calcium concentration were in the distal end of the fruit, and ranged from 0.038% in the dry day--dry night--low calcium treatment, where one fruit showed symptoms of blossom-end rot, to 0.120% in the humid day--humid night--high calcium treatment, where all fruits were normal. 3. - - Effects of nutrient strength by day and night on calcium concentration in tomato fruits was studied in this experiment. The concentration of calcium in the distal quarter of ripe fruit from plants grown in dilut~ nutrient solution at night was significantly higher than from those grown in concentrated solutions at night (Table V). Daytime concentrations had no significant effect.
Experiment
TABLE V E f f e c t o f day- a n d n i g h t - t i m e c o n c e n t r a t i o n o f t h e n u t r i e n t s o l u t i o n o n c a l c i u m concentratio:a (% o f d r y m a t t e r ) in t h e wall tissues f r o m t h e distal q u a r t e r o f ripe f r u i t o n t h e first a n d s e c o n d trusses o f t o m a t o c u l t i v a r ' E u r o c r o s s BB' ( E x p e r i m e n t 3) Day-time solution
Night-time solution Concentrated
Dilute
Mean
Concentrated
0.047
0.066
0.057 Ns
Dilute
0.051
0.065
0.058 Ns
Mean
0.049***
0.066***
L S D (P = 0 . 0 5 ) for individual c o m p a r i s o n s = 0.008. NS = d i f f e r e n c e n o t significant. *** d i f f e r e n c e significant a t P = 0.001. DISCUSS~ION
The association between calcium concentrations of less than about 0.05% of dry matter in fruit tissues and the occurrence of BER observed by earlier workers was confirmed. Low levels of calcium in fruits, particularly in the distal segment, were brought about by relatively dry atmospheric conditions, especially at night, and by relatively concentrated nutrient solutions, again especially at night, both circumstances that would be expected to result in relative]y weak root pressure. BER developed during the first 15 days or so after fruit set, as Barke (1968) found, and only in fruits on the first two trusses (Pill and Lambeth, 1980). Nevertheless, the intake of calcium into the fruits during the later stages of growth continued to be influenced by humidity and solution
216
concentration, so that the resulting differences in calcium content per fruit were substantial. The treatment combination of dry nights and concentrated nutrients reduced the calcium contents of whole fruit to less than half, and of the distal wall tissue to less than one third, of the values obtained from the humid night--dilute solution combination. When day-time and night-time concentrations of nutrients were different, only the concentration given at night affected the concentration of calcium in the distal wall tissue. A similar result has been obtained with strawberry, where the concentration of calcium in emerging leaves was affected by night-time but not by day-time nutrient concentration (Guttridge et al., 1981). The results of these experiments support the contention that the intake of calcium into plant organs which suffer restricted transpiration is dependent on the plant being exposed to environmental conditions that favour the development of root pressure (Palzkill et al., 1976). Maintaining high levels of humidity during the day has been found to restrict calcium uptake by the plant (Armstrong and Kirkby, 1979), so it would appear on this evidence that adequate transport of calcium into the fruit is best achieved by maintaining relatively humid conditions only at night, and by avoiding excessively concentrated solutions at the roots, at least during the early growth of the first and second truss.
REFERENCES
Armstrong, M.J. and Kirkby, E.A., 1979. The influence of humidity on the mineral composition of tomato plants with special reference to calcium distribution. Plant Soil, 52: 427--435. Barke, R.E., 1968. Absorption and translocation of calcium foliar sprays in relation to the incidence of blossom-end rot in tomatoes. Queensl. J. Agric. Anim. Sci., 25: 179--197. Bradfield, E.G. and Guttridge, C.G., 1979. The dependence of calcium transport and leaf tipburn in strawberry on relative humidity and nutrient solution concentration. Ann. Bot. (London), 43: 363--372. Cerda, A., Bingham, F.T. and Labanauskas, C.K., 1979. Blossom-end rot of tomato fruit as influenced by osmotic potential and phosphorous concentrations of nutrient solution media. J. Am. Soc. Hortic. Sci., 104: 236--239. Gerard, C.J. and Hipp, B.W., 1968. Blossom-end rot of 'Chico' and 'Chico Grande' tomatoes. Proc. Am. Soc. Hortic. Sci., 93:521--531. Guttridge, C.G., Bradfield, E.G. and Holder, R., 1981. Dependence of calcium transport into strawberry leaves on positive pressure in the xylem. Ann. Bot. (London), 48: 473--480. Millikan, C.R., Bjarnason, E.N., Osborn, R.K. and Hanger, B.C., 1971. Calcium concentration in tomato fruits in relation to the incidence of blossom~nd rot. Aust. J. Exp. Agric. Anita. Husb., 11: 570---575. Palzkill, D.A. and Tibbitts, T.W., 1977. Evidence that root pressure flow is required for calcium transport to head leaves of cabbage. Plant. Physiol., 60: 854--856. Palzkill, D.A., Tibbitts, T.W. and Williams, P.H., 1976. Enhancement of calcium transport to inner leaves of cabbage for prevention of tipburn. J. Am. Soc. Hortic. Sci., 101: 645--648.
217 Pill, W.G and Lambeth, V.N., 1980. Effects of soil water regime and nitrogen form on blossom-end rot, yield, water relations and elemental composition of tomato. J. Am. Soc. Hortic. Sci., 105: 730--734. Raleigh, S.M. and Chucka, J.A., 1944. Effect of nutrient ratio and concentration on growth and composition of tomato plants and on the occurrence of blossom-end rot of the fruit. Plant Physiol., 19: 671--678. Robbins, W.R., 1937. Relation of nutrient salt concentration to growth of the tomato and to the incidence of blossom-end rot of the fruit. Plant Physiol., 12: 21--50. Shaykewich, C.F., Yamaguchi, M. and Campbell, J.D., 1971. Nutrition and blossomend rot of tomatoes as influenced by soil water regime. Can. J. Plant Sci., 51: 505--511. Taylor, G.A. and Smith, C.B., 1957. The use of plant analysis in the study of blossomend rot of tomato. Proc. Am. Soc. Hortic. Sci., 70: 341--349. Turner, N.A., Ferguson, I.B. and Sharpies, R.O., 1977. Sampling and analysis for determining relationship of calcium concentration to bitter-pit in apple fruit. N.Z. J. Agric. Res., 20: 525--532. Van Goor, B.J., 1968. The role of calcium and cell permeability in the disease blossomend rot of tomatc, es. Physiol. Plant., 21: 1110--1121. Ward, G.M., 1973. Causes of blossom-end rot of tomatoes based on tissues analysis. Can. J. Plant Sci., 53: 169--174. Wiebe, H.J., Sch{itzler, H.P. and Kiihn, W., 1977. On the movement and distribution of calcium in white cabbage in dependence on the water status. Plant Soil, 48 : 409--416.
207
Elsevier Science Publishers B.V., Amsterdam - - P r i n t e d in The Netherlands
EFFECTS OF NIGHT-TIME HUMIDITY AND NUTRIENT SOLUTION CONCENTRATION ON THE CALCIUM CONTENT OF TOMATO FRUIT
E.G. B R A D F I E L D and C.G. G U T T R I D G E
Long Ashton Research Station, University of Bristol, Bristol (Gt. Britain) (Accepted for publication 13 July 1983)
ABSTRACT Bradfield, E.G. and Guttridge, C.G., 1984. Effects of night-time humidity and nutrient solution concentration on the calcium content of tomato fruit. Scientia Hortic., 22: 207--217. Calcium intake into tomato fruits was greater when nights were humid rather than dry and nutrient solutions dilute rather than concentrated. The concentration of calcium in the wall tissue o f the distal segment of fruits damaged by blossom-end rot was 0.03% of dry matter, but was 2- to 3-fold greater in the most favourable conditions of humidity and solution concentration, when fruits were undamaged. Adding extra calcium to the nutrient solution increased the calcium concentration in the proximal, but not in the middle or distal,segments of the fruit. The results support the hypothesis that a positive root pressure at night promotes transport of calcium into tissuesand organs that have restrictedtranspiration. Keywords: blossom-end rot; calcium; humidity; nutrient strength; tomato. ABBREVIATION B E R ~= blossom-end rot.
INTRODUCTION
Physiological disorders of plants caused by localised shortages of calcium occur in tissues that cannot readily transpire, and result from poor distribution of calcium rather than an overall deficiency in the plant. Environmental conditions that favour the development of positive root pressure at night promote calcium transport into the enclosed vegetative tissue of cabbage (Palzkill et al., 1976; Wiebe et al., 1977) and strawberry (Bradfield and Guttridge, 1979; Guttridge et al., 1981). Fruits, particularly in their later stages of development, have low transpiration rates and some show calcium-related disorders. Palzkill and Tibbitts (1977) suggested that adequate transport of calcium into fruits may depend, as it does for
0304-4238/84/$03.00
© 1984 Elsevier Science Publishers B.V.
208
some enclosed vegetative tissues, on root pressure flow. Although there seems to be little direct experimental evidence for fruits, Robbins (1937) found that very concentrated nutrient solutions, which would be expected to reduce root pressure, decreased guttation from leaves and increased the incidence of blossom-end rot (BER) in tomatoes. Blossom-end rot of tomatoes has been associated with a calcium concentration in the whole fruit of less than 0.2% dry weight (Raleigh and Chucka, 1944; Taylor and Smith, 1957), although Ward (1973) suggested that this value may be inaccurate. Later investigators determined calcium concentrations in the distal ends of fruits where the s y m p t o m s appear. Some report calcium concentrations in the distal end of 0.02--0.05% and > 0.07% in BER and normal fruit, respectively (Gerard and Hipp, 1968; van Goor, 1968; Ward, 1973; Cerda et al., 1979), whereas others found no relationship (Millikan et al., 1971; Shaykewich et al., 1971; Pill and Lambeth, 1980). Calcium concentration gradients in fruits and changes in concentration with growth make the choice of sample tissue critical (Turner et al., 1977; Bradfield and Guttridge, 1979). The experiments reported here were done to see whether the calcium c o n t e n t and concentration in tomato fruits was affected by humidity and nutrient concentrations, factors which are known to affect root pressure. MATERIALS AND METHODS 1. - - Tomato seedlings cultivar 'Ailsa Craig' were raised in sand culture and fed with nutrient solution A (Table I) diluted 4-fold. At the 4 full-leaf stage, 2 plants were transferred to each of 12 troughs (Bradfield and Guttridge, 1979) and suspended with their roots in nutrient solution A. Six troughs were placed in each of two growth rooms with a 16 h day and temperatures of 22 -+ 1.5°C by day and 18 + 1.0°C by night. Lighting was provided in this and subsequent experiments by warm white fluorescent lamps and tungsten filament lamps, in a rated wattage ratio of 15:1,
Experiment
TABLEI C o m p o s i t i o n and o s m o t i c potential (OP, kPa) of n u t r i e n t solutions (m equiv. 1 - ' ) . All solutions contained (p.p.m.): Fe, 5; Cu, 0.064; Mn, 0.55; B, 0.33; Zn, 0.065; Mo, 0.019 Ion
A
Ca 2+ I~ Mg 2+ Na ÷ NO~ H2PO ~ C1SO~ -
6 5 5 1.33 12.5 1.33 0.5 3
OP
--52
B 29 24 24 6.4 60 6.4 2.5 14.5 --254
C 13 5 5 1.33 12.5 1.33 1.5 9 --67
D 24 20 20 5.33 50 5.33 2 12 --208
209 at PAR levels between 270 and 330 pE m -2 s -1. After 7 days, the humidity of the rooms was changed to that of the experimental treatments, dry d a y / d r y night and dry d a y / h u m i d night, water vapour pressure deficits being 760 + 110 Pa and 260 + 110 Pa for dry and humid nights, respectively, and 1000 + 170 Pa for dry days, corresponding to mean relative humidities of 64 and 87% for nights and 61% for days, respectively. (Vapour p:ressure deficits and relative humidities were calculated from psychomet:cic measurements.) After a further 7 days, when the first truss commenced to flower, the nutrient solution in 3 troughs in each room was changed to Solution B (Table I}, the extra nutrient being added over a period of 4 days to avoid salt-induced wilting. Thus, there were 6 plants in each of the 4 treatments, humid or dry nights combined with dilute (A) or .concentrated (B) nutrient solutions. Solutions were replaced weekly t h r o u g h o u t the experiment. The plants grew normally and had set 6--7 trusses by the end of the experiment. Flowers were hand-pollinated daily. Dates of flowering and fruit set were recorded individually for all fruiting positions on the first two trusses on each plant. Eight fruits were harvested at each of 5 sizes -- 23, 26, 34, 41 and 51 m m diameter -- in each treatment, 4 from the first and 4 from the second trusses. The fruits were selected according to a pattern that gave equal representation of size categories to fruiting positions on the truss between 2 and 5 inclusive, the first fvaiting position n o t being harvested. These harvesting patterns were applied to trusses randomly. In all, 160 fruits were harvested and analysed individually. The fresh weight of each sampled fruit was recorded. The distal quarter was then severed and its jelly and seeds removed from the wall tissue and bulked with the remainder of the fruit. The calcium contents of the distal end wall tissue (including the skin) and of the remainder of the fruit were determiined separately. From these data, the calcium content and concentration of the distal wall tissue and of the whole fruit were calculated. The incidence of BER was recorded 2 4 and again 38 days after the first fruit truss had set. 2 . - - 'Ailsa Craig' plants were raised in sand and transferred to troughs containing solution A. Two troughs, each containing 3 plants, were transferred at the start of flowering of the first truss to each of three controlled-environment cabinets with a 16 h day. Mean dry bulb temperatures were 20 + 0.5°C during the day and 16 + 0.5°C at night. Water vapour pressure deficits were 400 + 60 Pa by day and ~ 100 Pa at night, corresponding to mean relative humidities of 83% by day and > 95% at night. The plants were stopped 2 or 3 leaves above the second truss. After 14 days, t:ae nutrient solution in one trough in each cabinet was changed to Solution C (Table I) and subsequently both solutions were replaced weekly. Humidities in the cabinets were then changed, where necessary, gradually over a period of 3 days to the 3 experimental treatments, dry d a y / d r y
Experiment
210 night, dry d a y / h u m i d night and humid d a y / h u m i d night, water vapour pressure deficits being 400 + 60 Pa for dry and < 100 Pa for humid conditions, corresponding to mean relative humidities of 83 and 78% for dry days and nights, respectively, and > 95% for humid days or nights. Two ripening fruits were harvested from each truss on each plant in each treatment, weighed and the calcium concentration determined in the proximal, middle and distal thirds of the fruit. 3. - - Tomato plants 'Eurocross BB' were raised in sand culture as before. At the 2 full-leaf stage, 6 plants were transferred to each of 4 troughs containing nutrient solution A (Table I) in a controlled-envir o n m e n t room at 22 + 1.5°C by day and 16 + I°C by night, and a daylength of 16 h. Water vapour pressure deficits were 920 + 170 Pa (65% RH) by day and 140 + 100 Pa (93% RH} at night. Flowers were handpollinated. Plants were stopped 2 leaves above the second truss and the experimental nutrient treatments then applied. One trough remained with dilute solution {A), another contained concentrated solution (D). The remaining two troughs contained either concentrated by day, dilute at night, or dilute by day, concentrated at night. There regimes were obtained by the pumping arrangements previously described for strawberry (Guttridge et al., 1981). The concentrated solution was built up in the first place by adding 4 daily increments. Solutions were changed every 3 days. Fruits were harvested as they ripened, and the calcium concentration determined in the wall tissues of the distal quarter of the fruit. Experiment
methods. - - Fruit samples were dried at 105°C, then ashed at 450°C. The residue was treated with 16 M nitric acid, dried and ashed again. The resulting white residue was dissolved in 0.5 M hydrochloric acid and made to volume. A portion was diluted with lanthanum chloride to give a concentration of 0.07 M La, and calcium was determined by atomic absorption spectroscopy at 4227 nm in an air--acetylene flame.
Analytical
treatment o f d a t a . - - Because the environmental treatments were n o t replicated, the between-plant variation within treatments was used as a measure of error to assess the significance of humidity and nutrient salt concentration.
Statistical
RESULT 1. - - In this experiment, we investigated the effects of nighttime humidity and of nutrient concentration on the calcium c o n t e n t of t o m a t o fruits at different stages of growth and on the calcium concentration in the wall tissue of the distal quarter of the fruit in relation to the incidence of blossom-end rot. The rate of intake of calcium into the fruits may be assessed against
Experiment
211
either increase in fruit weight or number of days from fruit set. Because fruits cannot be weighed before picking, we harvested at pre-defined fruit diameters. Although individual fruits varied slightly in shape, weights of fruits at a given harvest-diameter were not significantly different between treatments. Fruits grew significantly faster in dry nights combined with dilute nutrients (Fig. la), but differences were not great. Total calcium 50
40
LSD I
3O
I,Z
20
lO Ca)
0
--
'::)
~
'
115
'
2t5
!
315 | Days to pick
t 45
3600
LS 2800
. •2000 ¢0 1200
(b)
400 O
m
!
!
Days to pick
Fig. 1. (a) F r e s h weights o f t o m a t o fruits h a r v e s t e d at p r e d e t e r m i n e d d i a m e t e r s in Exp e r i m e n t 1, p l o t t e d against days f r o m f r u i t set t o harvest. Key t o t r e a t m e n t s : t = d r y n i g h t , ,dilute s o l u t i o n ; o ffi d r y n i g h t , c o n c e n t r a t e d s o l u t i o n ; • = h u m i d n i g h t , d i l u t e s o l u t i o n ; a = h u m i d night, c o n c e n t r a t e d s o l u t i o n . (b) As (a) b u t for c a l c i u m c o n t e n t s per fruit.
212
content of fruits increased most rapidly in humid nights combined with dilute solutions, and least rapidly in the opposite combination of dry nights and concentrated solutions (Fig. lb). Thus, Ca intake per day was decreased by dry nights and by concentrated solutions. The calcium concentration in the whole fruit (Fig. 2a) and in the distal segment (Fig. 2b) was already significantly different between some treatments at the first harvest (23 mm 10"0 '
8"0
6"0
u. o
4.0 ¸
8
o~ E
I
LSD
2.0
(a) i
~5
i
i
2s
i
3'5
i 45
i
Days to pick
0"11
LSD 0'09
0'07
.~" o . o s
0"03
O-Ol 0
(b) 0
I 5
i
1~5
I
;Z5
I
I I 35 Days to pick
415
Fig. 2. (a) A s F i g . l ( a ) b u t f o r c a l c i u m c o n c e n t r a t i o n s in f r u i t as m g p e r 1 0 0 g f r e s h weight. (b) As Fig. l ( a ) but for calcium percentage of dry matter in the distal quarter
of fruits.
213 d i a m e t e r ) . Calcium intake was greatest b o t h per d a y and per u n i t fruit weight in h u m i d nights and d i l u t e solutions, and least in d r y nights and c o n c e n ~ r a t e d solutions. In the later harvests, t h e overall d i f f e r e n c e s b e t w e e n e x t r e m e t r e a t m e n t s in calcium c o n c e n t r a t i o n in t h e distal s e g m e n t were m o r e t h a n 3-fold. Over t h e 5 successive harvests, t h e average effects o f b o t h night-time h u m i d i t y and n u t r i e n t strength were highly significant b o t h for calcium c o n t e n t per f r u i t and for c o n c e n t r a t i o n (Table II). T h e first and s e c o n d truss d i f f e r e d o n l y in days t o picking; the s e c o n d truss growing m o r e rapidly. D r y nights and c o n c e n t r a t e d solutions gave greatest n u m b e r s o f fruits with B E R (Table III). Nearly all t h e fruits t h a t were t o b e c o m e so were d a m a g e d b y the first r e c o r d i n g date. N o B E R o c c u r r e d in fruits on trusses 3 and 4. Because B E R d e v e l o p e d distally and early in f r u i t o n t o g e n y , mainly b e f o r e the s e c o n d harvest size (26 m m diameter}, calcium c o n c e n t r a t i o n s TABLE :[I Significance of variance ratios (F) for treatments in Experiment 1 Fruit parameter
Variable
pick
Fresh wt. (g)
Total Ca #g/100 g % dm #g/fruit F.W. (distal)
NS * ***
* NS NS
*** *** NS
Days
Night-time h u m i d i t y Nutrient c o n c e n t r a t i o n Truss
to
Concentration Ca
*** *** NS
*** *** NS
= not significant; *,***, respresenting significance at P = 0.05 and 0.001, respectively.
NS
TABLE III Number of fruits per plant showing external blossom-end rot on the first two trusses, recorded 24 and 38 days after the fruits had set (Experiment 1) Night-time h u m i d i t y Dry
Humid
Nutrient strength
Nutrient strength
Dilute
Concentrated
Dilute
Concentrated
Days
to recording Days to recording Days to recording Days to recording
24
38
24
38
24
38
24
38
]..7 (I.7
1.7 0.7
2.0 3.0
2.3 3.0
0.5 0
0.5 0
0 0
0 0
Total 2.4
2.4
5.0
5.3
0.5
0.5
0
0
Truss 1 2
214
only in the distal wall tissue and only at the first and second harvests are relevant to its incidence. At the first t w o harvests, the greatest and second greatest incidence of BER were associated with the lowest and second lowest concentrations of distal calcium in fruits from the dry--concentrated and dry--dilute treatments, respectively (Table III and Fig. 2b). Night-time humidity was apparently more important for BER than solution strength during the early, critical growth period in this experiment. Over all treatments, the mean concentrations of calcium in the distal wall tissue of fruits with BER was 0.031% of dry matter. 2. - - This experiment studied the effect of night- and daytime humidities and of a moderate increase in nutrient calcium, with chloride and sulphate anions (solution C compared with A), on calcium concentration in the proximal, middle and distal thirds of ripening tomato fruit 'Ailsa Craig' (Table IV). Calcium concentration was always much greater in the proximal end of the fruit than in the middle and distal portions. Increasing the amount of calcium in the nutrient solution increased the calcium concentration only in the proximal third.
Experiment
TABLE IV Effects of day- and night-time relative humidity and o f the concentration of calcium in the nutrient solution on the calcium concentration (% of dry matter) in the proximal, middle and distal thirds of ripe tomato fruits of the cultivar 'Ailsa Craig' (means of 12 fruits per treatment) Treatments Ca conc. (re.equiv.
% Ca Proximal
Middle
Distal
Dry/dry Dry/humid Humid/humid
0.107 0.172 0.206
0.047 0.068 0.116
0.038 0.072 0.112
Dry/dry Dry/humid Humid/humid
0.175 0.202 0.221
0.068 0.072 0.123
0.063 0.070 0.120
0.058
0.044
0.045
* * **
NS ** *
NS ** **
Day/night humidity
1-1)
13
LSD (P ffi 0.05) Significance of variance ratios (F) for the following: Ca in nutrient solution Day humidity Night humidity
NS = not significant; *, **, representing significance at P = 0.05 and 0.01, respectively.
215
Humid nights and humid days increased fruit calcium concentration significantly in all fruit segments, but it should be noted that night humidity comparisons were tested only following dry days, and day effects tested only following humid nights. The greatest increases in calcium concentration were in the distal end of the fruit, and ranged from 0.038% in the dry day--dry night--low calcium treatment, where one fruit showed symptoms of blossom-end rot, to 0.120% in the humid day--humid night--high calcium treatment, where all fruits were normal. 3. - - Effects of nutrient strength by day and night on calcium concentration in tomato fruits was studied in this experiment. The concentration of calcium in the distal quarter of ripe fruit from plants grown in dilut~ nutrient solution at night was significantly higher than from those grown in concentrated solutions at night (Table V). Daytime concentrations had no significant effect.
Experiment
TABLE V E f f e c t o f day- a n d n i g h t - t i m e c o n c e n t r a t i o n o f t h e n u t r i e n t s o l u t i o n o n c a l c i u m concentratio:a (% o f d r y m a t t e r ) in t h e wall tissues f r o m t h e distal q u a r t e r o f ripe f r u i t o n t h e first a n d s e c o n d trusses o f t o m a t o c u l t i v a r ' E u r o c r o s s BB' ( E x p e r i m e n t 3) Day-time solution
Night-time solution Concentrated
Dilute
Mean
Concentrated
0.047
0.066
0.057 Ns
Dilute
0.051
0.065
0.058 Ns
Mean
0.049***
0.066***
L S D (P = 0 . 0 5 ) for individual c o m p a r i s o n s = 0.008. NS = d i f f e r e n c e n o t significant. *** d i f f e r e n c e significant a t P = 0.001. DISCUSS~ION
The association between calcium concentrations of less than about 0.05% of dry matter in fruit tissues and the occurrence of BER observed by earlier workers was confirmed. Low levels of calcium in fruits, particularly in the distal segment, were brought about by relatively dry atmospheric conditions, especially at night, and by relatively concentrated nutrient solutions, again especially at night, both circumstances that would be expected to result in relative]y weak root pressure. BER developed during the first 15 days or so after fruit set, as Barke (1968) found, and only in fruits on the first two trusses (Pill and Lambeth, 1980). Nevertheless, the intake of calcium into the fruits during the later stages of growth continued to be influenced by humidity and solution
216
concentration, so that the resulting differences in calcium content per fruit were substantial. The treatment combination of dry nights and concentrated nutrients reduced the calcium contents of whole fruit to less than half, and of the distal wall tissue to less than one third, of the values obtained from the humid night--dilute solution combination. When day-time and night-time concentrations of nutrients were different, only the concentration given at night affected the concentration of calcium in the distal wall tissue. A similar result has been obtained with strawberry, where the concentration of calcium in emerging leaves was affected by night-time but not by day-time nutrient concentration (Guttridge et al., 1981). The results of these experiments support the contention that the intake of calcium into plant organs which suffer restricted transpiration is dependent on the plant being exposed to environmental conditions that favour the development of root pressure (Palzkill et al., 1976). Maintaining high levels of humidity during the day has been found to restrict calcium uptake by the plant (Armstrong and Kirkby, 1979), so it would appear on this evidence that adequate transport of calcium into the fruit is best achieved by maintaining relatively humid conditions only at night, and by avoiding excessively concentrated solutions at the roots, at least during the early growth of the first and second truss.
REFERENCES
Armstrong, M.J. and Kirkby, E.A., 1979. The influence of humidity on the mineral composition of tomato plants with special reference to calcium distribution. Plant Soil, 52: 427--435. Barke, R.E., 1968. Absorption and translocation of calcium foliar sprays in relation to the incidence of blossom-end rot in tomatoes. Queensl. J. Agric. Anim. Sci., 25: 179--197. Bradfield, E.G. and Guttridge, C.G., 1979. The dependence of calcium transport and leaf tipburn in strawberry on relative humidity and nutrient solution concentration. Ann. Bot. (London), 43: 363--372. Cerda, A., Bingham, F.T. and Labanauskas, C.K., 1979. Blossom-end rot of tomato fruit as influenced by osmotic potential and phosphorous concentrations of nutrient solution media. J. Am. Soc. Hortic. Sci., 104: 236--239. Gerard, C.J. and Hipp, B.W., 1968. Blossom-end rot of 'Chico' and 'Chico Grande' tomatoes. Proc. Am. Soc. Hortic. Sci., 93:521--531. Guttridge, C.G., Bradfield, E.G. and Holder, R., 1981. Dependence of calcium transport into strawberry leaves on positive pressure in the xylem. Ann. Bot. (London), 48: 473--480. Millikan, C.R., Bjarnason, E.N., Osborn, R.K. and Hanger, B.C., 1971. Calcium concentration in tomato fruits in relation to the incidence of blossom~nd rot. Aust. J. Exp. Agric. Anita. Husb., 11: 570---575. Palzkill, D.A. and Tibbitts, T.W., 1977. Evidence that root pressure flow is required for calcium transport to head leaves of cabbage. Plant. Physiol., 60: 854--856. Palzkill, D.A., Tibbitts, T.W. and Williams, P.H., 1976. Enhancement of calcium transport to inner leaves of cabbage for prevention of tipburn. J. Am. Soc. Hortic. Sci., 101: 645--648.
217 Pill, W.G and Lambeth, V.N., 1980. Effects of soil water regime and nitrogen form on blossom-end rot, yield, water relations and elemental composition of tomato. J. Am. Soc. Hortic. Sci., 105: 730--734. Raleigh, S.M. and Chucka, J.A., 1944. Effect of nutrient ratio and concentration on growth and composition of tomato plants and on the occurrence of blossom-end rot of the fruit. Plant Physiol., 19: 671--678. Robbins, W.R., 1937. Relation of nutrient salt concentration to growth of the tomato and to the incidence of blossom-end rot of the fruit. Plant Physiol., 12: 21--50. Shaykewich, C.F., Yamaguchi, M. and Campbell, J.D., 1971. Nutrition and blossomend rot of tomatoes as influenced by soil water regime. Can. J. Plant Sci., 51: 505--511. Taylor, G.A. and Smith, C.B., 1957. The use of plant analysis in the study of blossomend rot of tomato. Proc. Am. Soc. Hortic. Sci., 70: 341--349. Turner, N.A., Ferguson, I.B. and Sharpies, R.O., 1977. Sampling and analysis for determining relationship of calcium concentration to bitter-pit in apple fruit. N.Z. J. Agric. Res., 20: 525--532. Van Goor, B.J., 1968. The role of calcium and cell permeability in the disease blossomend rot of tomatc, es. Physiol. Plant., 21: 1110--1121. Ward, G.M., 1973. Causes of blossom-end rot of tomatoes based on tissues analysis. Can. J. Plant Sci., 53: 169--174. Wiebe, H.J., Sch{itzler, H.P. and Kiihn, W., 1977. On the movement and distribution of calcium in white cabbage in dependence on the water status. Plant Soil, 48 : 409--416.