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Samuel Salazar-García and Carol J. Lovatt

Botany at the Univ. of California. S. S-G. acknowledges the financial support of CONACYT, INIFAP and SNI of Mexico and the University of California, Riverside. We thank Charlie W. Coggins, Jr., for his advice on the selection of GA 3 concentrations and

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Willem J. Steyn, Samuel F. Ungerer, and Karen I. Theron

’ mandarin ( Talon et al., 1992 ), apple ( Bangerth and Schröder, 1994 ), and pear ( Deckers and Schoofs, 2002 ). Application of GA 3 during or shortly after anthesis increases parthenocarpic fruit set in various persimmon cultivars ( George et al., 1997

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Samuel Salazar-García, Luis E. Cossio-Vargas, Isidro J.L. González-Durán, and Carol J. Lovatt

growth and development and might prove useful as tools to achieve these goals. Gibberellic acid (GA 3 ) is the PBR that is most frequently reported to successfully alter the date and intensity of flowering in fruit trees. GA 3 application to mango

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Norman B. Best, Xingang Wang, Scottie Brittsan, Eric Dean, Seth J. Helfers, Ryan Homburg, Mariah L. Mobley, Tiffeny L. Spindler, Bofan Xie, Menglu Zhang, Paul M. Hasegawa, Robert J. Joly, David Rhodes, and Brian P. Dilkes

sunflower cultivar Sunspot. Comparisons of responses to GA 3 and uniconazole (UCZ), a GA biosynthetic inhibitor, application with the tall cultivar of sunflower Mammoth Grey indicated that ‘Sunspot’ is GA insensitive. Recently, Ramos et al. (2013) mapped

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Raguel Cano—M and Rebecca L. Darnell

The effects of different GA3 concentrations and application times on fruit set, fruit development period, and fruit quality in rabbiteye blueberry (Vaccinium ashei Reade) were studied. Flower clusters were sprayed with 100 or 250 ppm GA3 at 90% full bloom and again 7 days later, or with 125 ppm GA3 at 90% full bloom and again 7, 21, and 42 days later, under greenhouse conditions. Fruit set was monitored every 10 days and fruit weight, fruit development period, soluble solids, and titratable acidity were measured at harvest.

Fruit set in GA3 treatments averaged 69 to 76% compared to an average of 43% for the pollinated control. Weight of GA3 treated berries averaged 1.2, g while that of pollinated berries averaged 2.0 g. However, calculated total yield was greater for the GA3 treatments compared to the pollinated control, averaging 244 and 206 g/treatment, respectively. GA3 increased the fruit development period by 2 to 11 days, depending on the treatment. Soluble solids and titratable acidity were not affected by any treatment.

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Amy D. McDaniel* and Yin-Tung Wang

A study was initiated to determine the effect of GA3 as a counter measure to restore the growth of over-retarded poinsettia. Euphorbia pulcherrima `Sonora Red' plants were treated once foliarly with paclobutrazol at 40 or 80 mg·L-1 one week following pinching. Four weeks later, plants receiving the 80 mg·L-1 rate were treated once foliarly with GA3 at 0, 10, 20, 30 or 40 mg·L-1. The effect of GA3 was visible within 3 days of application. GA3 between 10 and 40 mg·L-1 caused long internodes, excessive stem elongation, as well as small leaves and bracts, resulting in unmarketable plants. Plants receiving 10 mg·L-1 GA3 were nearly twice the height of the over-retarded plants (31 vs. 17 cm), with increasingly taller plants at higher concentrations, up to 30 mg·L-1. In a second experiment, single-stemed plants were treated with one foliar spray of 50 or 150 mg·L-1 paclobutrazol two weeks following the beginning of short days. After another 3 weeks, the overdosed plants were then foliarly treated once with 0, 3, 5, 10, or 15 mg·L-1 GA3. GA3 at all rates promoted stem elongation and resulted in large bracts and much increased inflorescence diameter. The 15 mg·L-1 GA3 rate resulted in undesirable long internodes on the upper stem. Plants that received 3, 5, or 10 mg·L-1 GA3 were of excellent quality, with their heights and inflorescence sizes similar to those of plants receiving 50 mg·L-1 paclobutrazol (26 cm). Parallel experiments using `Burgundy Cortez' had similar results.

Open access

Tao Yuan, Qiuying Wei, and Gary Bauchan

regulator treatments, especially those including gibberellin ( Cadman et al., 2006 ). Germination of P. cernua seeds can increase to >92% if they are treated with kinetin, gibberellin GA3, and 2, 4-D for 24 h compared with 18% in untreated controls ( Gu et

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Fahed A. Al-Mana and Tajelsir I.M. Idris

Foliar spray of either BA or GA3 alone or in combinations of the two growth regulators were tested for their effects on Bryophyllum plants. Neither BA nor GA3 alone succeeded in stimulating lateral branching or flowering. GA3 totally inhibited bulbils formation. In a panel evaluating the ornamental quality, plants treated with GA3 at 100 ppm ranked top. The combination of BA and GA3 enhanced growth, branching, flowering and bulbils formation. The combinations of BA and GA3 at 50 ppm each, significantly improved the propagative qualities of the bulbils. Chemical names used: N-(phenylmethyl) -H purin-6-amine (BA), Giberllic acid (GA3).

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Raquel Cano-Medrano and Rebecca L. Darnell

To determine if multiple applications of GA3 would increase size of parthenocarpic fruit, and to assess the interaction between GA3 applications and pollination, `Beckyblue' rabbiteye blueberry (Vaccinium ashei Reade) flowers were treated with single or multiple applications of GA3 alone or in combination with full or partial pollination. Single or multiple applications of GA3 resulted in similar or increased fruit set compared with pollination, and increased fruit set compared with no pollination. GA3 applications decreased fruit mass and increased the fruit development period in comparison with pollination alone. Multiple, late applications of GA3 were ineffective in overcoming these effects. Partial (nonsaturating) pollination resulted in an average fruit set of 60%, while set following GA3 treatment in combination with full or partial pollination averaged 85%. Fruit mass was greater in the full pollination ±GA3 treatments than in all other treatments. The number of large seeds and seed mass per fruit were greatest in the full pollination treatment, and were significantly decreased by all treatments in which GA3 and/or partial pollination were used; however, there were no concomitant effects of GA3 in delaying the fruit development period. Our results indicate that under optimal pollination conditions, no detrimental effects of GA3 applications on fruit set, fruit size, or fruit development period in blueberry are to be expected, even though GA3 reduces seed number and seed mass. Furthermore, GA3 applications appear to be beneficial in increasing fruit set under suboptimal pollination conditions, although smaller fruit are to be expected under such conditions. Chemical name used: gibberellic acid (GA3).

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Kurt D. Nolte, Eugene A. Nothnagel, and Charles W. Coggins Jr.

Studies were conducted to determine whether certain physiological effects of gibberellic acid (GA3) on the peel of citrus fruits may be attributed to GA3 interaction with cellular membranes. Excised mesocarp tissue from pummelo [Citrus maxima (Burm.) Merrill] fruits was analyzed for electrolyte and K+ release over time in varying concentrations of GA3. Electrolyte leakage and K+ efflux was significantly reduced (up to 30%) when tissue was incubated in the presence of GA3. GA3 improved the viability of mechanically isolated protoplasts during 72 hr of storage at 7C, as shown by the use of fluorescein diacetate. These results suggest that some of the GA3-elicited responses in citrus fruits may be membrane related.