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The influence of daminozide and maleic hydrazide on growth and net photosynthesis of silver maple and American sycamore seedlings
Scientia Horticulturae, 19 (1983) 367--372
367
Elsevier Science Publishers B.V., A m s t e r d a m - Printed in The Netherlands
THE INFLUENCE OF DAMINOZIDE A N D MALEIC HYDRAZIDE ON GROWTH A N D NET PHOTOSYNTHESIS OF SILVER MAPLE A N D AMERICAN SYCAMORE SEEDLINGS
B.R. ROBERTS and S.C. DOMIR
U.S. Department of Agriculture, Agricultural Research Service, Nursery Crops Research Laboratory, Delaware, OH 43015 (U.S.A.) (Accepted for publication 8 June 1982)
ABSTRACT
Roberts, B.R. and Domir, S.C., 1983. The influence of daminozide and maleic hydrazide on growth and net photosynthesis of silver maple and American sycamore seedlings. Scientia Hortic., 19: 367--372. One-year-old seedlings of silver maple (Acer saccharinum L.) and American sycamore (Platanus occidentalis L.) were treated with daminozide [ butanedioic acid mono (2,2-dimethylhydrazide)] or maleic hydrazide (1,2-dihydro-3,6-pyridazine dione) via stem injection. Six weeks after treatment with maleic hydrazide, plants of both species were shorter, had less leaf area and less total dry weight than untreated plants. During the same period, daminozide reduced plant height and leaf area of treated maple seedlings while reducing leaf area and total dry weight of treated sycamore. Daminozide had no influence on height of sycamore or total dry weight of silver maple. Both chemicals caused a decrease in net photosynthesis; however, seedlings injected with daminozide overcame this effect 2--3 weeks after treatment.
INTRODUCTION
Because of costs associated with vegetation management, particularly along utility rights-of-way, there has been renewed interest in the use of chemical growth retardants to control tree height (Abbott, 1977; Domir, 1978). This is especially true of trunk injection, a technique which offers obvious ecological advantages over existing spray procedures as an economical means of controlling the size of woody vegetation (Kozel et al., 1970; Roberts, 1980). Numerous chemicals have been tested for their effectiveness in controlling tree growth (Sachs et al., 1967; Frank et al., 1973; Cathey, 1975; Alvarez, 1977; Domir, 1978). Specifically, two growth regulators, maleic hydrazide (1,2-dihydro-3,6-pyridazine dione) and daminozide [ butanedioic acid m o n o (2,2-dimethylhydrazide)], have been utilized in extensive field testing to determine the effectiveness of trunk injection as a means of controlling regrowth in landscape trees (Brown et al., 1977; Roberts et al., 1979). Since the management of trees can be particularly crucial in urban areas where 0304-4238/83/$03.00
© 1983 Elsevier Science Publishers B.V.
368 vegetation is under continual scrutiny by the public, this study was undertaken to determine possible inhibitory effects of these growth regulators on net photosynthesis and growth of silver maple and American sycamore seedlings under greenhouse conditions. MATERIALS AND METHODS Twenty-four seedlings each of silver maple (Acer saccharinu'm L.) and American sycamore (Platanus occidentalis L.} were planted in 20-cm-diameter plastic containers in a mixture of 2 peat: 1 perlite:l soil (v/v/v) and placed in the greenhouse during early April. In June, after the seedlings were in full leaf, each plant was pruned back to about 35 cm in height, resulting in the removal of about one-third of the existing foliage. One week later, net photosynthesis was measured on each seedling by infrared gas analysis using a closed system described elsewhere (Roberts, 1972). After determining a base photosynthetic rate, serum vial caps were affixed to the main stem of each plant using the technique described by Gregory (1969). The serum caps served as a reservoir for subsequent chemical treatment (Ufferman et ah, 1979}. Six seedlings each of silver maple and American sycamore were treated with commercial formulations of daminozide (5.0 g 1"1) or maleic hydrazide (3.0 g 1"1) by adding 5 ml of chemical solution to each serum cap reservoir before wounding the stem with a scalpel. A similar procedure was followed with 6 additional seedlings of each species, except that the latter plants were treated with 5 ml of water (control). The serum caps were left in place until all the liquid (either daminozide, maleic hydrazide or water) was absorbed through wounds made in the stem, after which the caps were removed to prevent possible girdling of young stem tissue. At intervals of 1, 2, 3 or 6 weeks after injection, net photosynthesis of all seedlings was re-measured and data for chemically-treated seedlings expressed as a percentage of the corresponding water-treated control plants. All 48 plants in the study were harvested after 6 weeks and measurements taken of height, total leaf area, and dry weight of leaves, stems and roots. The data were analyzed statistically and comparisons made between treated and untreated plants of each species. RESULTS AND DISCUSSION Daminozide and maleic hydrazide inhibited the growth of silver maple and American sycamore seedlings, but both species were affected more by maleic hydrazide than by daminozide (Table I). Although the leaf area of daminozide-treated maple and sycamore seedlings was less than untreated controls, height growth of sycamore was unaffected by this chemical. This is an important consideration in utility rights-of-way maintenance, because shoot length determines the time at which re-trimming is required (Abbott, 1976). Leaf, stem, and total dry weights were all significantly less in damino-
369
zide-treated sycamore than in the control plants, whereas only stem dry weight was significantly less in treated silver maple (Table I). This rather inconsistent response to daminozide treatment is not altogether uncommon, even among woody plants of the same species (Halfacre et al., 1968), and may reflect, to some degree, the method by which the chemical was applied. While considerable variability in regrowth control was observed for seedlings of maple and sycamore treated with daminozide, practically no variability was noted when the same species were injected with maleic hydrazide. Height growth, leaf area and stem dry weight were all reduced when compared with untreated control (Table I). Only root dry weight of maleic hydrazide-injected sycamore seedlings was not significantly affected by chemical treatment. This latter observation may have resulted from the fact that maleic hydrazide influences root initiation rather than root development (Bhattacharya and Varsha, 1981). TABLEI The effect of stem-injected daminozide and maleic hydrazide on the growth of 1-year-old silver maple and American sycamore seedlings 6 weeks after treatment Chemical
Concentration (g l ' )
Height (cm)
Leaf Dry weight (g) area (cm 2) Leaves Stems
Roots
Total
Silver maple Daminozide Maleic hydrazide Control
5.0 3.0
81.5" 38.5* 129.4
316" 59* 541
17.3 7.2* 26.4
11.9" 8.5* 18.8
10.2 8.4* 10.7
39.4 24.1" 55.9
American sycamore Daminozide Maleic hydrazide Control
5.0 3.0
93.7 33.0* 98.6
379* 51" 565
21.1" 8.1" 26.1
12.7" 8.5* 17.7
9.3 8.6 11.4
43.1" 25.3* 55.2
* Significantly different from the control at P = 0.05.
Net photosynthetic measurements made on daminozide- and maleic hydrazide-treated seedlings of silver maple and American sycamore gave contrasting results (Figs. 1 and 2). Although both chemicals caused an initial decline in net photosynthesis, daminozide-treated plants recovered after 2--3 weeks, whereas COs exchange in maleic hydrazide-treated seedlings continued to decline throughout the 6-week sampling period. Ferree and Hall (1978) reported that a single application of 2000 mg 1"1 daminozide had no measurable influence on net photosynthesis of greenhouse-grown apple trees. The concentration of daminozide used in the present study, however, was considerably higher and may account for at least part of this difference. The decrease in net photosynthesis observed in maleic hydrazide-treated maple and sycamore seedlings is consistent with the growth data reported in
370 i
I
f
T
Daminozide
i,o :. : Sycamore o - - . . o Silver m a p l e I
I
I
]
J
1
2
3
4
5
T i m e after t r e a t m e n t ( w e e k s )
Fig. 1. The effect of a single treatment of daminozide (5.0 g ]-1) on net photosynthesis of silver maple and American sycamore seedlings 1, 2, 3 and 6 weeks following stem injection. Each value represents the mean of 6 seedlings and is expressed as a percentage of 6 untreated (control) plants. Average net photosynthetic rates for control seedlings were 4.9 and 4.8 mg CO 2 dm "2 h "z for maple and sycamore, respectively. I
I
I
I
I
100, Maleic Hydrazide
'Eo 0
80
\
-
c---o
Silver m a p l e
-
q,I
cO.
1
2
3 .
4
5
Time after t r e a t m e n t (weeks) Fig. 2. The effect of a single treatment of maleic hydrazide (3.0 g l "1) on net photosynthesis of silver maple and American sycamore seedlings 1, 2, 3 and 6 weeks following stem injection. Each value represents the mean of 6 seedlings and is expressed as a percentage of 6 untreated (control) plants. Average net photosynthetic rates for control seedlings were 5.8 and 4.5 mg CO 2 dm "2 h "1 for maple and sycamore, respectively.
371 Table I. As noted earlier, maleic hydrazide had a significant effect on height growth, leaf area, and dry weight of both species, and this is reflected in the photosynthetic response of injected plants (Fig. 2). Although published reports suggest that maleic hydrazide suppresses plant metabolism (Kozel et al., 1970; Shanmugam and Muthuswamy, 1974; Mueller and Mondy, 1977), the influence of the chemical on photosynthesis is not well documented. Wort and Singh (1970) demonstrated an increase in the photosynthetic rate of maleic hydrazide-treated sugar beets, while Koske and Svec (1975) reported that certain aspects of photosynthesis, namely the Hill reaction and dichlorophenol indophenol reduction, were significantly decreased in maleic hydrazide-treated bean chloroplasts. The decline in net photosynthesis observed in our study may result either from the direct influence of maleic hydrazide on the photosynthetic mechanism per se, or from the indirect effect of the chemical on stomatal opening, such as reported by Inamdar and Gangadhara (1975). CONCLUSION The data from this study verify the growth-regulating potential of daminozide when injected into the stems of 1-year-old silver maple and American sycamore seedlings. Of the 2 chemicals tested, maleic hydrazide more consistently controlled height growth, leaf area and dry weight of both species, while daminozide did not affect height growth in American sycamore or total dry weight in silver maple. The results of this investigation also indicate the need for additional research to determine the long-range effects of maleic hydrazide on growth of trees in highly visible urban areas, since data obtained with maple and sycamore seedlings show significant reductions in net photosynthesis 6 weeks after treatment. ACKNOWLEDGEMENTS The research reported in this paper was supported, in part, by the nursery industry through contributions to the Horticultural Research Institute -- a non-profit organization devoted to progress through research.
REFERENCES
Abbott, R.E., 1976. New concept in utility arboriculture. J. Arboric., 2: 148--150. Abbott, R.E., 1977. Commercialarboricultural practices in North America.J. Arboric., 3: 141--145. Alvarez, R.G., 1977. Growth regulators. J. Arboric., 3: 94--97. Bhattachaxya, J. and Varsha, G., 1981. Mode of action of dikegulac, fusicoccin, maleic hydrazide and their interactions with red and fad-red light on rooting cuttings of Phaseolus mungo cultivar G31 in relation to auxin and nutrition. Indian J. Exp. Biol., 19: 158--164.
372 Brown, G.K., Kwolek, W.F., Wuertz, D.E., Jumper, G.A., Wilson, C.L. and Carr, S.R., 1977. Regrowth reduction in American elm and sycamore by growth regulator injection. J. Am. Soc. Hortic. Sci., 102: 748--751. Cathey, H.M., 1975. Comparative plant growth-retarding activities of ancymidol with ACPC, phosphon, chlormequat, and SADH on ornamental species. HortScience, 10: 204--216. Domir, S.C., 1978. Chemical control of tree height. J. Arboric., 4: 145--153. Ferree, D.C. and Hall, F.R., 1978. Effects of growth regulators and multiple applications of pesticides on net photosynthesis and transpiration of greenhouse-grown apple trees. J. Am. Soc. Hortic. Sci., 103: 61--64. Frank, J.R., Creager, R.A., Whigam, T.L. and Havrinen, W.A., 1973. Evaluation of twentyfive growth retardants on seedling trees in the greenhouse. Proc. Northwest Weed Sci. Soc., 27 : 120. Gregory, G.F., 1969. A technique for inoculating plants with vascular pathogens. Phytopathology, 59: 1014. Halfacre, R.G., Barden, J.A. and Rollins, H.A., Jr., 1968. Effects of Alar on morphology, chlorophyll content, and net CO 2 assimilation rate of young apple trees. J. Am. Soc. Hortic. Sci., 93: 40--52. Inamdar, J.A. and Gangadhara, M., 1975. Effect of growth regulators on stomata] structure and development in cotyledons of Lagenaria leucantha. Aust. J. Bot., 23: 13--26. Koske, T.J. and Svec, L., 1975. Some effects of maleic hydrazide on light reactions of photosynthesis in isolated chlorophasts from Phaseolus vulgaris plants. Can. J. Plant. Sci., 55: 145--149. Kozel, P.C., Reisch, K.W. and Hull, G.E., 1970. Chemical control of tree growth. Ohio Rep., 55 : 104--105. Mueller, T.O. and Mondy, N.I., 1977. Effect of sprout inhibition on the lipid composition of potatoes. J. Food Sci., 42: 618--621. Roberts, B.R., 1972. Net photosynthesis, growth, and transpiration in American elm seedlings as influenced by Dutch elm disease and plant-water stress. Phytopathology, 62: 457--459. Roberts, B.R., 1980. Advances in tree growth control by trunk injection. J. Arboric., 6: 57---63. Roberts, B.R., Wuertz, D.E., Brown, G.K. and Kwolek, W.F., 1979. Controlling sprout growth in shade trees by trunk injection. J. Am. Soc. Hortic. Sci., 104: 883--887. Sachs, R.M., Hackett, W.P., Maire, R.G., Baldwin, R. and Kretchum, T., 1967. Chemical control of vegetative growth of woody ornamental plants. Proc. Am. Soc. Hortic. Sci., 91 : 728--734. Shanmugam, .4~ and Muthuswamy, S., 1974. Influence of photoperiod and growth regulators on the nutrient status of chrysanthemum. Indian J. Hortic., 31: 186--193. Ufferman, D.G., Roberts, B.R., Brown, G.K., Carr, S.R. and Kwolek, W.F., 1979. Regrowth control by chemical injection in seedlings of four tree species. HortScience, 14 : 749-75O. Wort, D.J. and Singh, B., 1970. Growth, composition, and metabolic responses of sugar beet to preharvest application of maleic hydrazide. Agron. J., 62: 57--60.
367
Elsevier Science Publishers B.V., A m s t e r d a m - Printed in The Netherlands
THE INFLUENCE OF DAMINOZIDE A N D MALEIC HYDRAZIDE ON GROWTH A N D NET PHOTOSYNTHESIS OF SILVER MAPLE A N D AMERICAN SYCAMORE SEEDLINGS
B.R. ROBERTS and S.C. DOMIR
U.S. Department of Agriculture, Agricultural Research Service, Nursery Crops Research Laboratory, Delaware, OH 43015 (U.S.A.) (Accepted for publication 8 June 1982)
ABSTRACT
Roberts, B.R. and Domir, S.C., 1983. The influence of daminozide and maleic hydrazide on growth and net photosynthesis of silver maple and American sycamore seedlings. Scientia Hortic., 19: 367--372. One-year-old seedlings of silver maple (Acer saccharinum L.) and American sycamore (Platanus occidentalis L.) were treated with daminozide [ butanedioic acid mono (2,2-dimethylhydrazide)] or maleic hydrazide (1,2-dihydro-3,6-pyridazine dione) via stem injection. Six weeks after treatment with maleic hydrazide, plants of both species were shorter, had less leaf area and less total dry weight than untreated plants. During the same period, daminozide reduced plant height and leaf area of treated maple seedlings while reducing leaf area and total dry weight of treated sycamore. Daminozide had no influence on height of sycamore or total dry weight of silver maple. Both chemicals caused a decrease in net photosynthesis; however, seedlings injected with daminozide overcame this effect 2--3 weeks after treatment.
INTRODUCTION
Because of costs associated with vegetation management, particularly along utility rights-of-way, there has been renewed interest in the use of chemical growth retardants to control tree height (Abbott, 1977; Domir, 1978). This is especially true of trunk injection, a technique which offers obvious ecological advantages over existing spray procedures as an economical means of controlling the size of woody vegetation (Kozel et al., 1970; Roberts, 1980). Numerous chemicals have been tested for their effectiveness in controlling tree growth (Sachs et al., 1967; Frank et al., 1973; Cathey, 1975; Alvarez, 1977; Domir, 1978). Specifically, two growth regulators, maleic hydrazide (1,2-dihydro-3,6-pyridazine dione) and daminozide [ butanedioic acid m o n o (2,2-dimethylhydrazide)], have been utilized in extensive field testing to determine the effectiveness of trunk injection as a means of controlling regrowth in landscape trees (Brown et al., 1977; Roberts et al., 1979). Since the management of trees can be particularly crucial in urban areas where 0304-4238/83/$03.00
© 1983 Elsevier Science Publishers B.V.
368 vegetation is under continual scrutiny by the public, this study was undertaken to determine possible inhibitory effects of these growth regulators on net photosynthesis and growth of silver maple and American sycamore seedlings under greenhouse conditions. MATERIALS AND METHODS Twenty-four seedlings each of silver maple (Acer saccharinu'm L.) and American sycamore (Platanus occidentalis L.} were planted in 20-cm-diameter plastic containers in a mixture of 2 peat: 1 perlite:l soil (v/v/v) and placed in the greenhouse during early April. In June, after the seedlings were in full leaf, each plant was pruned back to about 35 cm in height, resulting in the removal of about one-third of the existing foliage. One week later, net photosynthesis was measured on each seedling by infrared gas analysis using a closed system described elsewhere (Roberts, 1972). After determining a base photosynthetic rate, serum vial caps were affixed to the main stem of each plant using the technique described by Gregory (1969). The serum caps served as a reservoir for subsequent chemical treatment (Ufferman et ah, 1979}. Six seedlings each of silver maple and American sycamore were treated with commercial formulations of daminozide (5.0 g 1"1) or maleic hydrazide (3.0 g 1"1) by adding 5 ml of chemical solution to each serum cap reservoir before wounding the stem with a scalpel. A similar procedure was followed with 6 additional seedlings of each species, except that the latter plants were treated with 5 ml of water (control). The serum caps were left in place until all the liquid (either daminozide, maleic hydrazide or water) was absorbed through wounds made in the stem, after which the caps were removed to prevent possible girdling of young stem tissue. At intervals of 1, 2, 3 or 6 weeks after injection, net photosynthesis of all seedlings was re-measured and data for chemically-treated seedlings expressed as a percentage of the corresponding water-treated control plants. All 48 plants in the study were harvested after 6 weeks and measurements taken of height, total leaf area, and dry weight of leaves, stems and roots. The data were analyzed statistically and comparisons made between treated and untreated plants of each species. RESULTS AND DISCUSSION Daminozide and maleic hydrazide inhibited the growth of silver maple and American sycamore seedlings, but both species were affected more by maleic hydrazide than by daminozide (Table I). Although the leaf area of daminozide-treated maple and sycamore seedlings was less than untreated controls, height growth of sycamore was unaffected by this chemical. This is an important consideration in utility rights-of-way maintenance, because shoot length determines the time at which re-trimming is required (Abbott, 1976). Leaf, stem, and total dry weights were all significantly less in damino-
369
zide-treated sycamore than in the control plants, whereas only stem dry weight was significantly less in treated silver maple (Table I). This rather inconsistent response to daminozide treatment is not altogether uncommon, even among woody plants of the same species (Halfacre et al., 1968), and may reflect, to some degree, the method by which the chemical was applied. While considerable variability in regrowth control was observed for seedlings of maple and sycamore treated with daminozide, practically no variability was noted when the same species were injected with maleic hydrazide. Height growth, leaf area and stem dry weight were all reduced when compared with untreated control (Table I). Only root dry weight of maleic hydrazide-injected sycamore seedlings was not significantly affected by chemical treatment. This latter observation may have resulted from the fact that maleic hydrazide influences root initiation rather than root development (Bhattacharya and Varsha, 1981). TABLEI The effect of stem-injected daminozide and maleic hydrazide on the growth of 1-year-old silver maple and American sycamore seedlings 6 weeks after treatment Chemical
Concentration (g l ' )
Height (cm)
Leaf Dry weight (g) area (cm 2) Leaves Stems
Roots
Total
Silver maple Daminozide Maleic hydrazide Control
5.0 3.0
81.5" 38.5* 129.4
316" 59* 541
17.3 7.2* 26.4
11.9" 8.5* 18.8
10.2 8.4* 10.7
39.4 24.1" 55.9
American sycamore Daminozide Maleic hydrazide Control
5.0 3.0
93.7 33.0* 98.6
379* 51" 565
21.1" 8.1" 26.1
12.7" 8.5* 17.7
9.3 8.6 11.4
43.1" 25.3* 55.2
* Significantly different from the control at P = 0.05.
Net photosynthetic measurements made on daminozide- and maleic hydrazide-treated seedlings of silver maple and American sycamore gave contrasting results (Figs. 1 and 2). Although both chemicals caused an initial decline in net photosynthesis, daminozide-treated plants recovered after 2--3 weeks, whereas COs exchange in maleic hydrazide-treated seedlings continued to decline throughout the 6-week sampling period. Ferree and Hall (1978) reported that a single application of 2000 mg 1"1 daminozide had no measurable influence on net photosynthesis of greenhouse-grown apple trees. The concentration of daminozide used in the present study, however, was considerably higher and may account for at least part of this difference. The decrease in net photosynthesis observed in maleic hydrazide-treated maple and sycamore seedlings is consistent with the growth data reported in
370 i
I
f
T
Daminozide
i,o :. : Sycamore o - - . . o Silver m a p l e I
I
I
]
J
1
2
3
4
5
T i m e after t r e a t m e n t ( w e e k s )
Fig. 1. The effect of a single treatment of daminozide (5.0 g ]-1) on net photosynthesis of silver maple and American sycamore seedlings 1, 2, 3 and 6 weeks following stem injection. Each value represents the mean of 6 seedlings and is expressed as a percentage of 6 untreated (control) plants. Average net photosynthetic rates for control seedlings were 4.9 and 4.8 mg CO 2 dm "2 h "z for maple and sycamore, respectively. I
I
I
I
I
100, Maleic Hydrazide
'Eo 0
80
\
-
c---o
Silver m a p l e
-
q,I
cO.
1
2
3 .
4
5
Time after t r e a t m e n t (weeks) Fig. 2. The effect of a single treatment of maleic hydrazide (3.0 g l "1) on net photosynthesis of silver maple and American sycamore seedlings 1, 2, 3 and 6 weeks following stem injection. Each value represents the mean of 6 seedlings and is expressed as a percentage of 6 untreated (control) plants. Average net photosynthetic rates for control seedlings were 5.8 and 4.5 mg CO 2 dm "2 h "1 for maple and sycamore, respectively.
371 Table I. As noted earlier, maleic hydrazide had a significant effect on height growth, leaf area, and dry weight of both species, and this is reflected in the photosynthetic response of injected plants (Fig. 2). Although published reports suggest that maleic hydrazide suppresses plant metabolism (Kozel et al., 1970; Shanmugam and Muthuswamy, 1974; Mueller and Mondy, 1977), the influence of the chemical on photosynthesis is not well documented. Wort and Singh (1970) demonstrated an increase in the photosynthetic rate of maleic hydrazide-treated sugar beets, while Koske and Svec (1975) reported that certain aspects of photosynthesis, namely the Hill reaction and dichlorophenol indophenol reduction, were significantly decreased in maleic hydrazide-treated bean chloroplasts. The decline in net photosynthesis observed in our study may result either from the direct influence of maleic hydrazide on the photosynthetic mechanism per se, or from the indirect effect of the chemical on stomatal opening, such as reported by Inamdar and Gangadhara (1975). CONCLUSION The data from this study verify the growth-regulating potential of daminozide when injected into the stems of 1-year-old silver maple and American sycamore seedlings. Of the 2 chemicals tested, maleic hydrazide more consistently controlled height growth, leaf area and dry weight of both species, while daminozide did not affect height growth in American sycamore or total dry weight in silver maple. The results of this investigation also indicate the need for additional research to determine the long-range effects of maleic hydrazide on growth of trees in highly visible urban areas, since data obtained with maple and sycamore seedlings show significant reductions in net photosynthesis 6 weeks after treatment. ACKNOWLEDGEMENTS The research reported in this paper was supported, in part, by the nursery industry through contributions to the Horticultural Research Institute -- a non-profit organization devoted to progress through research.
REFERENCES
Abbott, R.E., 1976. New concept in utility arboriculture. J. Arboric., 2: 148--150. Abbott, R.E., 1977. Commercialarboricultural practices in North America.J. Arboric., 3: 141--145. Alvarez, R.G., 1977. Growth regulators. J. Arboric., 3: 94--97. Bhattachaxya, J. and Varsha, G., 1981. Mode of action of dikegulac, fusicoccin, maleic hydrazide and their interactions with red and fad-red light on rooting cuttings of Phaseolus mungo cultivar G31 in relation to auxin and nutrition. Indian J. Exp. Biol., 19: 158--164.
372 Brown, G.K., Kwolek, W.F., Wuertz, D.E., Jumper, G.A., Wilson, C.L. and Carr, S.R., 1977. Regrowth reduction in American elm and sycamore by growth regulator injection. J. Am. Soc. Hortic. Sci., 102: 748--751. Cathey, H.M., 1975. Comparative plant growth-retarding activities of ancymidol with ACPC, phosphon, chlormequat, and SADH on ornamental species. HortScience, 10: 204--216. Domir, S.C., 1978. Chemical control of tree height. J. Arboric., 4: 145--153. Ferree, D.C. and Hall, F.R., 1978. Effects of growth regulators and multiple applications of pesticides on net photosynthesis and transpiration of greenhouse-grown apple trees. J. Am. Soc. Hortic. Sci., 103: 61--64. Frank, J.R., Creager, R.A., Whigam, T.L. and Havrinen, W.A., 1973. Evaluation of twentyfive growth retardants on seedling trees in the greenhouse. Proc. Northwest Weed Sci. Soc., 27 : 120. Gregory, G.F., 1969. A technique for inoculating plants with vascular pathogens. Phytopathology, 59: 1014. Halfacre, R.G., Barden, J.A. and Rollins, H.A., Jr., 1968. Effects of Alar on morphology, chlorophyll content, and net CO 2 assimilation rate of young apple trees. J. Am. Soc. Hortic. Sci., 93: 40--52. Inamdar, J.A. and Gangadhara, M., 1975. Effect of growth regulators on stomata] structure and development in cotyledons of Lagenaria leucantha. Aust. J. Bot., 23: 13--26. Koske, T.J. and Svec, L., 1975. Some effects of maleic hydrazide on light reactions of photosynthesis in isolated chlorophasts from Phaseolus vulgaris plants. Can. J. Plant. Sci., 55: 145--149. Kozel, P.C., Reisch, K.W. and Hull, G.E., 1970. Chemical control of tree growth. Ohio Rep., 55 : 104--105. Mueller, T.O. and Mondy, N.I., 1977. Effect of sprout inhibition on the lipid composition of potatoes. J. Food Sci., 42: 618--621. Roberts, B.R., 1972. Net photosynthesis, growth, and transpiration in American elm seedlings as influenced by Dutch elm disease and plant-water stress. Phytopathology, 62: 457--459. Roberts, B.R., 1980. Advances in tree growth control by trunk injection. J. Arboric., 6: 57---63. Roberts, B.R., Wuertz, D.E., Brown, G.K. and Kwolek, W.F., 1979. Controlling sprout growth in shade trees by trunk injection. J. Am. Soc. Hortic. Sci., 104: 883--887. Sachs, R.M., Hackett, W.P., Maire, R.G., Baldwin, R. and Kretchum, T., 1967. Chemical control of vegetative growth of woody ornamental plants. Proc. Am. Soc. Hortic. Sci., 91 : 728--734. Shanmugam, .4~ and Muthuswamy, S., 1974. Influence of photoperiod and growth regulators on the nutrient status of chrysanthemum. Indian J. Hortic., 31: 186--193. Ufferman, D.G., Roberts, B.R., Brown, G.K., Carr, S.R. and Kwolek, W.F., 1979. Regrowth control by chemical injection in seedlings of four tree species. HortScience, 14 : 749-75O. Wort, D.J. and Singh, B., 1970. Growth, composition, and metabolic responses of sugar beet to preharvest application of maleic hydrazide. Agron. J., 62: 57--60.