Foliar Spray Of Gibberellic Acid Research Articles

Response of Phosphorus, Sulphur and Foliar Spray of GA3 on Nutrient Content and Uptake of Soybean [Glycine max (L.) Merrill

Background: Soybean is an important oil seed crop grown in a varied range of climate and soils in India. Phosphorous and sulphur is an important macronutrient required for plants. Their deficiency in soil is a worldwide concern for production of oil seed crops. The gibberellic acid involved in plant growth and development. Therefore, investigation was carry out to study influenced of phosphorus, sulphur and gibberellic acid on nutrient content and uptake of soybean. Methods: An experiment conducted during kharif-2020 on soybean in sub-sub split plot design with three replications. The twenty four treatment combinations were comprised viz. four levels of phosphorus (Control, 20, 40 and 60 kg ha-1), three levels of sulphur (15, 30 and 45 kg ha-1) and two levels of gibberellic acid (Foliar spray of GA3 @ 75 ppm and no spray). Result: Results revealed that application of 40 kg phosphorus ha-1 and 30 kg sulphur ha-1 is optimum dose for obtaining higher available nitrogen, phosphorus, potassium and sulphur in the soil after crop harvest, nutrient content in seed and straw and uptake of soybean crop. The foliar spray of gibberellic acid @ 75 ppm is also beneficial for improving productivity and profitability of soybean crop.

Influence of Foliar Application of Growth Regulators on Vegetative Growth and Flowering Of Chrysanthemum

The pot experiment was conducted at the Floriculture field of Horticulture Research Centre (HRC), Bangladesh Agricultural Research Institute (BARI), Gazipur during August 2020 to May 2021 to evaluate the foliar spray of gibberellic acid (GA3), benzyl adenine (BA) and naphthalene acetic acid (NAA) on growth and flowering traits of chrysanthemum (Chrysanthemum morifolium). The experiment was laid out in Randomized Complete Block Design (RCBD) with three replications. Four weeks old seedlings of chrysanthemum genotype CM-019 (flower class: Pompon and flower colour: Orange yellow) were transplanted in pot keeping under natural sunlight. The aqueous solution of GA3, BA and NAA @ 100 and 200 ppm of each were sprayed on the flower plants at monthly interval starting after one month of transplantation of seedlings along with control (water). The results revealed that vegetative growth and flowering parameters were significantly influenced by plant growth regulators. Maximum number of leaves per plant (50.0) and leaf area per plant (7.5 cm2) were recorded from the spraying of BA @ 100 ppm closely followed by BA @ 200 ppm (48.0 and 7.0 cm2/plant) and GA3 @ 100 ppm only for number of leaves (47.0/plant). Spraying of GA3 @ 100 ppm produced the tallest plant (70.0 cm) and the highest plant spread (23.0 cm). Number of flowers (26.0/plant), flower size (7.8 cm), average weight of stalk (37.0 g) and vase life (15.0 days) were also found maximum from the application of GA3 @ 100 ppm, closely followed by GA3 @ 200 ppm (23.5/plant, 7.2 cm, 36.0 g, 14.0 days) and NAA @ 100 ppm (18.5/plant, 7.0 cm, 36.0 g, 13.0 days) and irrespective of concentrations, BA failed to improve these characters. GA3 @ 100 ppm recorded maximum length of stalk (37.5 cm) and rachis (29.0 cm), which was identical with GA3 @ 200 ppm (34.6 cm and 25.0 cm), and BA @ 100 ppm gave the lowest length of stalk and rachis. GA3 also caused faster initiation of flowering, whereas NAA and BA delayed it. GA3 @ 100 ppm took the minimum days to flowering (50.0 days) was observed when plants were sprayed with GA3 @ 100 ppm whereas it was maximum (69 days) from BA @ 100 ppm treatment. It can be concluded that GA3 @ 100 ppm provided the best results for obtaining better vegetative growth of plants, maximum number of cut blooms with longer stalk as well as bigger flower size with prolonged vase life in chrysanthemum.
 Bangladesh J. Agril. Res. 47(1): 69-80, March 2022

Effect of Phosphorus, Sulphur and Gibberellic Acid on Growth, Root Nodules and Yield of Soybean [Glycine max (L.) Merrill

An experiment was conducted during kharif season 2020 at Instructional Farm, College of Agriculture, Ummedganj, Kota. The experiment comprised twenty-four treatment combinations, having four levels of phosphorus viz., 0, 20, 40 and 60 kg ha-1, three levels of sulphur viz., 15, 30 and 45 kg ha-1 and foliar spray of gibberellic acid viz., no spray and spray of GA3 @ 75 ppm laid out in sub-sub split-plot design with three replications. Results showed that application of 60 kg P2O5 ha-1 had significant effect on plant height, dry matter accumulation plant-1, branches plant-1 at 30, 60 DAS and at harvest, root nodules plant-1 and their dry weight at 45 DAS while root nodules plant-1 and their dry weight at 45 DAS andseed yield (1956 kg ha-1) over application of 40, 20 kg P2O5 ha-1 and control. Significantly higher seed yield (1956 kg ha-1) was recorded under application of 60 kg P2O5 ha-1 over application of 20 kg P2O5 ha-1 and control. However, it was found at par with application of 40 kg P2O5 ha-1. Application of 45 kg sulphur ha-1 had significantly higher plant height (cm) at 60 DAS and at harvest, dry matter accumulation (g plant-1) at 30, 60 and at harvest stages, branches plant-1 at 30, 60 and at harvest stage, number of root nodules and their dry weight (g) and seed yield (1742 kg ha-1) which was found at par with application of 30 kg sulphur ha-1 over 15 kg sulphur ha-1. Application of gibberellic acid @ 75 ppm as foliar spray gave significantly higher plant height (cm) at 60 DAS and at harvest stage, dry matter accumulation (g plant-1) at 60 DAS and at harvest, branches plant-1 at 30, 60 DAS and harvestand seed yield (1770 kg/ha) over control.

Effect of foliar spray of gibberellic acid (GA3) and borax on growth, productivity, and quality of tomato (Lycopersicon esculentum Mill.) under protected structure at Kaski, Nepal

Tomato (Lycopersicon esculentum Mill.) is a highly demanded solanaceous vegetable crop in Nepal. Poor vegetative growth, low flowering and fruit set are the major problems in tomato. Thus, an experiment was conducted to improve vegetative growth, flowering, fruiting and productivity of tomato (Nepali Variety Type 2) at Pokhara-14, Kaski, Nepal during spring- summer of 2019 in Split plot arrangement with gibberellic acid (GA3) as main factor and Borax as sub factor, with three replications. The main factor consisted of four concentrations of GA3 (0, 25, 50 and 75 ppm) which was applied thrice as foliar spray at 15, 30 and 45 days after transplanting (DAT) and sub factor consisted three concentrations of borax (0%, 0.25% and 0.5%) which was applied four times as foliar spray at 15, 30, 45 and 60 DAT. Growth characters viz., plant height, leaf area, leaf number, flower number per cluster, fruit number were significantly enhanced with application of 50 ppm GA3 and gave higher productivity (31.65 t ha-1) compared to other concentrations and control. Likewise, foliar spray of borax resulted in higher stem girth, flower clusters, number of flowers per cluster, and TSS content of tomato. Furthermore, borax @ 0.25% gave the highest productivity (30.78 t ha-1). The better effect of 50 ppm GA3 on growth and yield of tomato and effect of 0.25% borax on flowering and yield, makes them promising solutions to the problems of tomato at Kaski, Nepal. Thus, further research should be conducted by using GA3 and borax in several other tomato cultivars in field and under protected structure at different soil type and climatic conditions.

Non-Structural Carbohydrates, Foliar Nutrients, Yield Components and Oxidative Metabolism in Pecan Trees in Response to Foliar Applications of Growth Regulators

Foliar sprays of growth regulators have commercial potential for improving the performance of some of the parameters associated with alternate bearing in pecan trees. The objective was to evaluate the behaviour of alternate bearing through analysis of seasonal variations in buds and leaflets of non-structural carbohydrates (glucose, fructose, sucrose, and starch), mineral nutrients (N-total, P, K+, Ca2+, Mg2+, Fe2+, Cu2+, Mn2+ and Zn2+), yield components (nut weight per kilogram and kernel percentage) and oxidative metabolism (superoxide dismutase, hydrogen peroxide, catalase, guaiacol peroxidase and antioxidant capacity) in cv. Wichita pecan trees in response to foliar applications of gibberellic acid (50 mg L−1), calcium prohexadione (500 mg L−1) or thidiazuron (10 mg L−1). The experiment was of a completely randomized experimental design with five replicates. Foliar growth regulator (GRs) sprays help maintain the concentration of non-structural carbohydrates in the leaflets and buds between the evaluation years. With the exception of K+ (12.9 and 10.9 g kg−1) and Zn2+ (45.1 and 30.5 mg kg−1), the GRs did not show any effects on the concentrations of the foliar mineral nutrients. The results suggest foliar sprays of gibberellic acid improve the performance of parameters associated with alternate bearing, including oxidative metabolism.

Efficacy of various doses of salicylic acid, naphthalene acetic acid and gibberellic acid on vegetative growth and pod yield of broad bean (Vicia faba L.)

To investigate the efficacy of various doses of plant growth regulators on vegetative growth and pod yield of broad bean (Vicia faba L.), a field experiment was accomplished at Vegetable Research Farm, B.H.U., Varanasi during the winter season of 2019-20. Ten treatments were evaluated in randomized block design with three replications. Results indicated that the growth parameters like plant height, number of branches/plant significantly increased with foliar spray of gibberellic acid followed by NAA and salicylic acid. The yield attributes like pod width, fresh pod weight, number of pods/plant as well as fresh pod yield significantly enhanced by NAA followed by gibberellic acid and salicylic acid with various concentrations, respectively. The foliar spraying of 120 ppm GA3 tended to produce plant with maximum height (116.4 cm), number of branches/plant (6.3), pod length (7.5 cm), number of seeds/pod (4.6) as well as early 50 % flowering (57.3 days) whereas, spraying of 40 ppm NAA exhibited the maximum pod width (1.3 cm), fresh pod weight (4.6 g), number of pods/plant (87.5) as well as fresh pod yield (105.0 q ha-1) as compared to other treatments. The maximum net return (Rs. 337326.5 ha-1) was recorded with 40 ppm NAA with B: C ratio of 3.65 followed by 30 ppm NAA and 20 ppm NAA. The lowest net income (Rs. 162382.5 ha-1) and B: C ratio (1.76) was obtained from control. The spraying of NAA was found superior in terms of yield and yield attributes as well as benefit cost ratio followed by GA3 and salicylic acid.

Efficacy of various doses of salicylic acid, naphthalene acetic acid and gibberellic acid on vegetative growth and pod yield of broad bean (Vicia faba L.)

To investigate the efficacy of various doses of plant growth regulators on vegetative growth and pod yield of broad bean (Vicia faba L.), a field experiment was accomplished at Vegetable Research Farm, B.H.U., Varanasi during the winter season of 2019-20. Ten treatments were evaluated in randomized block design with three replications. Results indicated that the growth parameters like plant height, number of branches/plant significantly increased with foliar spray of gibberellic acid followed by NAA and salicylic acid. The yield attributes like pod width, fresh pod weight, number of pods/plant as well as fresh pod yield significantly enhanced by NAA followed by gibberellic acid and salicylic acid with various concentrations, respectively. The foliar spraying of 120 ppm GA3 tended to produce plant with maximum height (116.4 cm), number of branches/plant (6.3), pod length (7.5 cm), number of seeds/pod (4.6) as well as early 50 % flowering (57.3 days) whereas, spraying of 40 ppm NAA exhibited the maximum pod width (1.3 cm), fresh pod weight (4.6 g), number of pods/plant (87.5) as well as fresh pod yield (105.0 q ha-1) as compared to other treatments. The maximum net return (Rs. 337326.5 ha-1) was recorded with 40 ppm NAA with B: C ratio of 3.65 followed by 30 ppm NAA and 20 ppm NAA. The lowest net income (Rs. 162382.5 ha-1) and B: C ratio (1.76) was obtained from control. The spraying of NAA was found superior in terms of yield and yield attributes as well as benefit cost ratio followed by GA3 and salicylic acid.

EFFECT OF FOLIAR SPRAYS OF GIBBERELLIC ACID ON NODULE NUMBER SHOOT AND ROOT LENGTH OF PHASEOLUS ACONITIFOLIUS

The effect of foliar spray of gibberellic acid on nodule number, shoot and root length was studied. Gibberellic acid inhibited the number of nodules at all the three concentrations. Maximum inhibition in the number of nodule was noted at 100 ppm concentration whereas the shoot and root length showed better growth.

EFFECT OF GIBBERELLIC ACID CONCENTRATIONS AND RUNNERS' REMOVAL RATES ON YIELD AND QUALITY OF FRIGO STRAWBERRY PLANTATIONS

This experiment was carried out at a private farm in Shoney Village, Tanta, El-Gharbia Governorate, Egypt, during the two successive seasons of 2014/2015 and 2015/2016 to study the effect of runners' removal rates beside mothers full removal no runners, five runners left, ten runners left and Without runners' removaland foliar spray of gibberellic acid 0 ppm, 25 ppm and 50 ppm and their interactions on vegetative growth, chemical properties, physiological traits, yield and quality of strawberry Fortuna cv. planted under mixed planting system which fixed many runners beside mother plant with different density. Gibberellic acid (GA3) was sprayed three time in 30 days intervals. The experimental design was a split plot in a randomized complete block design with three replications. The result indicated that foliar application of 25 ppm of gibberellic acid (GA3) with removing all runners caused an increase in plant height, size, weight and shape index of the fruits. gibberellic acid (GA3) at 25 ppm gave also the highest number of early fruits and early yield during both seasons,GA3 also gave the highest value of TSS, vitamin C, number of leaves, number of fruits and the yield too. The study shows that it's better to use gibberellic acid (GA3) with 25 ppm to spray the strawberry fruits with removing all the runners that exist beside the mother plant and that's to increase the vegetative growth and to improve the yield qualities.

Application of foliar spray of gibberellic acid and nitrogen on the Marigold quantitatively and qualitatively (Tagetes erecta and Tagetes patula L.)

A critical investigation was carried out to define the optimal amount of nitrogen and gibberellic acid to produce quality of flowers in Marigold flower during 2011-2012. The research was passed carried out randomly in seven Blocks and doses comprised six degrees of nitrogen (weekly and fourteen days periodically), doses of GA3 (0, 50 and 100 ppm) and two cultivars (Tagetes erecta and Tagetes patula). The 65.94 cm of plant height was noted with nitrogen 1000 ppm per week and GA 3 100 ppm utilized double. GA 3 at 50 ppm form buds of 1.83 cm in size. 6.96 cm flower diameters were eminent having nitrogen dose of 500 while GA 3 of 50 ppm. Nitrogen of 1000 ppm/week determined a sum of 7.25 flowers per plant. 58.25 cm were the stem length noted treated by 1000 ppm/week of Nitrogen and GA 3.

Effect of Foliar Applied Benzyladenine and Gibberellic Acid on Vegetative Growth and Chemical ConsTituents of Dracaena marginata. (B) Pinched Plants.

The present study was carried-out at Antoniades Research Branch, Horticulture Research Institute, A.R.C. Alexandria, Egypt during the two successive seasons of 2013 and 2014. In this study, we aimed to test the effect of applying foliar sprays of gibberellic acid and benzyladenine in increasing the marketing quality of Dracaena marginata plants. Dracaena small plants were planted individually in 30 cm diameter plastic pots. The small plants were pinched to length to 30 cm from soil surface. The plants were sprayed with gibberellic acid at the concentrations of 500, 1000 and 1500 mg/L and benzyladenine at the concentrations of 200, 250 and 300 mg/L. The obtained results showed that spraying with gibberellic acid at 1000 mg/L and benzyladenine at 300 mg/L together increased significantly plant height, leaves number per plant, leaves dry weight, leaves area, stem diameter, stem dry weight, branches number per plant, root length and root dry weight. The obtained results showed that spraying with gibberellic acid at 1000 mg/L and benzyladenine at 250 mg/L together resulted in the highest chlorophyll content, carbohydrates content and nitrogen percentage in the leaves.

Modification of Sex Expression in Sagittaria latifolia by the Application of Gibberellic Acid and Paclobutrazol

A clear modification of sex expression in Sagittaria latifolia from male or trimonoecious to female was induced by a foliar spray of gibberellic acid (GA) at concentrations of 10, 100, and 1000 ppm. This modification began two weeks after the initiation of treatment. The effect was greater at a higher GA concentration. The number of racemes was increased by the treatment. On the other hand, male and perfect flowers were produced in the female line by a foliar spray of paclobutrazol (PBZ) at concentrations of 100 and 1000 ppm two weeks after the initiation of treatment, and a greater number of male flowers was produced in the trimonoecious line by the spray. The number of racemes was decreased by the PBZ application. GA was effective for the internode elongation of rachises and scapes; on the contrary, PBZ was effective in shortening the internodes. Therefore, it was clarified that endogenous GA controlled sex expression, raceme production, and internode length in this species. Female flowers in the male line developed into fruits with a normal seed; further, female flowers that had been pollinated with pollen grains from male flowers of the female line also developed into fruits with a normal seed. These results will be useful for the breeding of S. latifolia.

Gibberellic acid affects growth and flowering of Philodendron ‘Black Cardinal’

A single foliar spray of gibberellic acid (GA3) at concentrations of 125, 250, 500, or 1,000 mg L−1 induced flowering of Philodendron‘Black Cardinal’ (an interspecific hybrid developed from a series of crosses among P. wendlandii, hastatum, erubescens, imbe, fragrantissimum, and an unnamed species) in approximately 170 d. Percentage of plants induced and mean flower number per plant increased as GA3 concentrations increased. Compared to unsprayed plants, the number of new leaves decreased, petiole lengths of new leaves and length of the largest leaf increased, but leaf width was unaffected among sprayed plants. One hour before the spathe started to unfurl, spadix temperatures increased, and temperatures in the male portion of the spadix rose by 10 °C above ambient as the spathe fully opened. Elevated temperatures were recorded for about two hours and returned to ambient within five hours. Spathes remained open for about five hours. A creamy white spadix with a contrasting burgundy spathe resulted in more aesthetically pleasing plants than with foliage alone. Because of the short period of display, the open spathe would not increase additional ornamental value of Philodendron‘Black Cardinal’ in the marketplace. However, if breeding is the purpose of flowering induction, spathes should be cut away from the spadix to facilitate pollination.

Effects of gibberellic acid and temperature on growth and root carbohydrates of Delphinium seedlings

Delphinium ‘Blue Bird’ seedlings weregrown in heated (air temperature >15 ) and unheatedglasshouses in winter and treated with foliar sprays of gibberellic acid(GA3) or drenched with uniconazole (UZ). The unheated seedlings wereexposed to temperatures as low as 5 . Under bothheated and unheated growing conditions, leaf differentiation was retarded by theGA3 application. Leaves of the unheated seedlings showed very littleexpansion, but the GA3 application stimulated leaf expansion underchilled conditions. Root starch and mannitol decreased and root sucroseincreased during cold acclimation. These changes were less in theGA3-treated seedlings than in the non-treated seedlings. The higherstarch and mannitol contents in GA3-treated seedlings indicates thatthe GA3 application inhibits starch and mannitol utilization orconversion to sucrose. Chilling hastened flowering but the GA3application did not. GA3 application during the chilling periodincreased spike volume, probably because under chilled conditions, the seedlingsto which GA3 was applied expanded their leaves and were able toassimilate more than the seedlings not receiving GA3. These results suggest that exogenous GA3 apparently breaksthe rosette by means of rapid enlargement of already differentiated tissues andthat the action of exogenous GA3 is, essentially, different from thatof the chilling treatment.

Gibberellin and temperature effects on dormancy release and shoot morphogenesis of mango ( Mangiferaindica L.)

Single foliar sprays of gibberellic acid (GA 3) (10–250 mg l −1) were applied during cool or warm temperatures to determine their effects on shoot initiation and morphogenesis in mango ( Mangifera indica L.) cv. Keitt and Tommy Atkins. Dormant, non-differentiated axillary buds were released by removing the apical inflorescence (deblossoming) in flowering shoots, or by heading the terminal vegetative flush (intercalary unit) in vegetative stems. Buds of non-treated and GA 3-treated stems initiated growth during exposure to cool (about 26°C day/15°C night outdoors or 18°C day/10°C night in a growth chamber) or warm temperatures (outdoors at about 29°C day/25°C night or 30°C day/25°C night in a growth chamber). Buds initiated inflorescences despite GA 3 treatment when morphogenesis occurred during exposure to cool, floral-inductive temperatures outdoors or in the growth chamber. A single GA 3 treatment delayed initiation of inflorescences on deblossomed orchard stems, but not on headed vegetative stems. GA 3 treatment resulted in vegetative shoot production only when buds differentiated during exposure to warm temperature conditions either outdoors or in a growth chamber. Thus, GA 3 delayed inflorescence initiation but did not cause vegetative morphogenesis when bud differentiation occurred in cool temperatures. In contrast to delaying inflorescence initiation in cool temperatures, GA 3 did not delay vegetative growth during warm temperatures. Thus, it is concluded that GA 3 prevents initiation of reproductive shoots of mango rather than inhibiting floral induction.

Flower Bud Thinning and Winter Survival of `Redhaven' and `Cresthaven' Peach in Response to GA3 Sprays

The timing and concentration of dilute foliar sprays of gibberellic acid (GA3) were tested for their flower bud thinning effect during three consecutive years on two common cultivars of peach [Prunus persica (L.) Batsch.] grown in commercial culture under midwestern conditions. There was a strong trend for June sprays to minimize the total flower bud density (buds/cm shoot) of unbranched shoots on mature `Redhaven' and `Cresthaven' trees. The GA3 treatments applied between early July and late October did not reduce the total flower bud density. Increasing the concentration from 25 or 50 mg·L-1 to 200 mg·L-1 tended to decrease total flower bud density, especially when applied May through July. During the same period the GA3 treatments reduced total flower bud density of short shoots (<10 cm), but only about two-thirds as effectively as on long shoots. The `Redhaven' live flower density on trees treated in May, June or September was up to 2 times greater then the control in March following exposure to extreme fluctuations in winter temperatures to near critical lows in 1988 and 1989. Although 50 mg·L-1 GA3 applied in June 1989 reduced total flower bud density by 70%, it resulted in a live flower density only 35% lower than the control. The treatment induced 2.3 times greater survival of the total flower buds existing after thinning when winter temperatures gradually declined to critical levels. The increased live flower density caused by the GA3 sprays translated to a cropload 1.3 to 2.25 times greater than control. The length of neither fruiting quality shoots in the bearing canopy nor 1-year-old upright branched shoots in the top of trees (watersprouts) was appreciably affected by the GA3 applications. GA3 treatments at 100 and 200 mg·L-1 in late July and early August slightly delayed time of full bloom. Defoliation was delayed slightly by treatments applied in September and late July. Moderate doses of appropriately timed GA3 sprays reduced flower bud densities without adverse effects on winter survival, yield, defoliation or bloom time. Our results support the use of GA3 as a reliable peach thinning tool.

Photoperiod, Temperature, Gibberellin, and an Anti-gibberellin Affect Tuberization of Potato Stem Segments In Vitro

`Katahdin' potato plants were grown under conditions that did not induce tuberization (noninducing conditions) and the foliage was sprayed with either a growth retardant (BAS-111) at 1000 mg·L-1 or distilled water. Other plants, grown under tuber-inducing conditions, received a foliar spray of gibberellic acid (GA3) at 100 mg·L-1 or distilled water. After 1 week, treatments were repeated. Two-node stem segments were excised from the apical, subapical, medial, and basal sections of each plant 72 hours after the second foliar treatment, disinfested, and inserted into flasks containing 50 mL of Murashige and Skoog medium (2% sucrose). After 3 weeks in a darkened incubator adjusted to 24 °C, tuberization response was evaluated. Orthogonal contrasts revealed significant differences between induced and noninduced controls for tuber number, diameter, and fresh mass. BAS-111 reduced rhizome length and increased tuber number, diameter, and fresh mass. GA3 increased rhizome length, but reduced tuber number, diameter, and fresh mass. Node location influenced tuber development, as basal explants produced significantly more and larger tubers, as well as longer rhizomes, than did apical explants, and subapical segments produced more and larger tubers than did apical segments. There were no significant differences between medial and basal nodal segments with respect to tuber number or tuber/rhizome size. Chemical names used: 1-phenoxy-5,5-dimethyl-3-(1,2,4-triazol-1-yl)-hexan-5-ol (BAS-111); 2,4a,7-trihydroxy-1-methyl-8-methylenegibb-3-ene-1,10-carboxylic acid 1->4 lactone (GA3).

Effect of gibberellic acid and nitrogen on carbonic anhydrase activity and mustard biomass

In mustard(Brassica juncea L.) addition of 20 mM nitrogen (in the form of NaNO3) inhibited after 50 d the activities of carbonic anhydrase and nitrate reductase and net photosynthetic rate. However, when nitrogen was applied in association with the foliar spray of gibberellic acid, the inhibition was reversed and the above parameters and also leaf area index and dry mass were enhanced.

Gibberellic Acid Reverses Effects of Excess Paclobutrazol on Geranium

Paclobutrazol (PBZ) was applied to `Mustang' geranium (Pelargonium × hortorum L.H. Bailey) as a single growth-medium drench at 0.06 mg a.i./pot or as a single foliar spray at 100 mg·liter-l when the plants had three to four expanded true leaves (34 days after sowing). At these rates, PBZ caused excessive growth suppression but plants flowered earlier than untreated controls. A single foliar spray of gibberellic acid (GA) at 100 mg·liter-l applied 0 (same day), 7, 14, or 21 days after PBZ reversed the growth suppression caused by PBZ. Plants treated with GA30 or 7 days after PBZ were as tall or taller and flowered at the same time as or later than the untreated (no PBZ, no GA3) controls. Plants treated with GA, 14 or 21 days after PBZ were shorter and flowered earlier than untreated controls but were taller than plants treated with PBZ alone. Response to GA3 was similar whether PBZ was applied as a drench or as a spray. Chemical name used: (+)-(R*,R*)-β([4-chlorophenyl]methyl)-α-(1,1-dimethylethyl)-1 H -1,2,4-triazole-1-ethanol (paclobutrazol).

Influence of gibberellin A3 and ancymidol on sunflower leaf anatomy

The plant growth retardant ancymidol (α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol), when sprayed at 132 mg/L of active ingredient, increased leaf thickness, palisade cell length, and number of cells per unit length, and decreased intercellular space percentage in developing Helianthus annuus L. (sunflower) cv. Mammoth Russian leaves when plants were grown under 400 or 1500 μmol∙s−1∙m−2 photosynthetic photon flux density. Foliar sprays of gibberellic acid at 10–40 mg/L reversed the effects of ancymidol on leaf anatomy. Stomatal density and total stomata per adaxial leaf surface area were increased by ancymidol sprays.