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Anil P. Ranwala, Garry Legnani and William B. Miller

Several experiments were conducted to find effective ways of utilizing gibberellin4+7 (GA4+7) and benzyladenine (BA) to prevent leaf chlorosis during greenhouse production of Easter lilies (Lilium longiflorum Thunb.) while minimizing the undesirable side effects on stem elongation. On an absolute concentration basis, GA4+7 was much more effective than BA in preventing leaf chlorosis. Excessive levels of GA4+7, however, tended to cause stem elongation. When applied at around the visible bud stage, if the foliage was well covered with the spray solution, 25 mg·L-1 of GA4+7 was adequate for maximum protection against leaf chlorosis. Increasing the GA4+7 concentration above 25 mg·L-1 gave no additional benefit on leaf chlorosis. Two possible modes of GA4+7 uptake during a foliar spray application (absorption through leaves and stems, and root uptake of the extra run-off) were studied in terms of their relative contribution to leaf chlorosis and stem elongation. Although both modes of uptake prevented leaf chlorosis, foliar uptake was much more effective than root uptake. However, GA4+7 taken up by the roots contributed mainly to stem elongation. When sprayed to leaves on only the lower half of the plant, a 10-mL spray of either 25 or 50 mg·L-1 of each GA4+7 and BA was enough for complete protection against leaf chlorosis. Increasing volumes had no additional benefit on leaf chlorosis, but increased the chances of unwanted stem elongation.

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Ryo Fukui, Saori Kikuchi, Yuko Ichida and Hitoshi Honjo

Effects of postimportation treatment of benzyladenine (BA) on vase life of imported anthurium flowers was examined after receiving the flowers in Japan and placing them either individually or together in vase solution. Cut anthuriums of two cultivars imported from Hawaii via air-freight were sprayed with 200 μg·m L–1 of BA upon arrival, and vase life of the flowers were evaluated by numerating days before observing apparent discoloration at the distal end of spadix. BA treatment significantly extended the vase life (by up to 22 d) in two cultivars in most cases during summer, but the effect was inconsistent in each cultivar when the test was done in winter. The effect of BA verified in summer was either nullified or significantly diminished by placing 10 flowers together in vase solution. In these tests, bacteria were isolated more frequently from the scape segments of bunched flowers than those of individual flowers. However, vase life was not affected when the vase solutions were inoculated with Xanthomonas axonopodis pv. dieffenbachiae. These results indicate that the postimportation BA treatment is mostly effective in extending the vase life of cut anthuriums during summer, but may not be reliable during winter in temperate regions. The preliminary evidence suggests that bacterial growth in vase solution be related to the loss of the effect of BA, but the pathogen of bacterial blight growing in the vase solution or invading the xylem of the scape is not responsible for the reduced longevity of imported anthuriums.

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Constance A. Parks and Thomas H. Boyle

The effects of stratification, BA, thiourea, and GA3 were examined on germination of Liatris spicata (L.) Willd. seed. Seeds were germinated at 20 °C and numbers of germinated seed were counted daily for 21 days. The final germination percentage (G) for seeds stored dry at 4 °C for 0 to 10 weeks ranged from 52% to 64%, while stratification at 4 °C for 10 weeks increased G to 98% and decreased the days to 50% of final germination (T50) and the days between 10% and 90% germination (T90-T10). Aqueous solutions of BA at 10 or 100 mg·L-1 applied to blotter paper increased G and decreased T50 but did not affect T90-T10. In a separate experiment, dry seeds were treated for 3 minutes in BA at 0 to 1126 mg·L-1 dissolved in acetone. G values increased quadratically, whereas T50 and T90-T10 values decreased quadratically in response to BA concentration. A 3-minute preplant acetone permeation of seeds with BA at 225 or 1127 mg·L-1 yielded G and T50 values similar to those obtained with 10 weeks of stratification. Seeds immersed in thiourea at 0.76 or 7.61 mg·L-1 for 24 hours prior to sowing had higher G and lower T50 values than controls (0 mg·L-1 thiourea), but T90-T10 values were similar for all treatments. Seeds treated with GA3 at 1, 10, or 100 mg·L-1 in H2O did not differ from controls (0 mg·L-1 GA3) in G, T50, or T90-T10. Infusion of BA via acetone may be a practical means of breaking seed dormancy and accelerating germination in L. spicata. Chemical names used: N-(phenylmethyl)-1H-purine-6-amine [benzyladenine (BA)]; gibberellic acid (GA3); thiocarbamide (thiourea).

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Anil P. Ranwala and William B. Miller

Experiments were conducted to evaluate storage temperature, storage irradiance and prestorage foliar sprays of gibberellin, cytokinin or both on postharvest quality of Oriental hybrid lilies (Lilium sp. `Stargazer'). Cold storage of puffy bud stage plants at 4, 7, or 10 °C in dark for 2 weeks induced leaf chlorosis within 4 days in a simulated consumer environment, and resulted in 60% leaf chlorosis and 40% leaf abscission by 20 days. Cold storage also reduced the duration to flower bud opening (days from the end of cold storage till the last flower bud opened), inflorescence and flower longevity, and increased flower bud abortion. Storage at 1 °C resulted in severe leaf injury and 100% bud abortion. Providing light up to 40 μmol·m-2·s-1 during cold storage at 4 °C significantly delayed leaf chlorosis and abscission and increased the duration of flower bud opening, inflorescence and flower longevity, and reduced bud abortion. Application of hormone sprays before cold storage affected leaf and flower quality. ProVide (100 mg·L-1 GA4+7) and Promalin (100 mg·L-1 each GA4+7 and benzyladenine (BA)) effectively prevented leaf chlorosis and abscission at 4 °C while ProGibb (100 mg·L-1 GA3) and ABG-3062 (100 mg·L-1 BA) did not. Accel (10 mg·L-1 GA4+7 and 100 mg·L-1 BA) showed intermediate effects on leaf chlorosis. Flower longevity was increased and bud abortion was prevented by all hormone formulations except ProGibb. The combination of light (40 μmol·m-2·s-1) and Promalin (100 mg·L-1 each GA4+7 and BA) completely prevented cold storage induced leaf chlorosis and abscission.

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Ed Stover, Mike Fargione, Richard Risio, Xiaoe Yang and Terence Robinson

Thinning with BA reportedly increases size of 'Empire' fruit more than does thinning with NAA because of enhancement of cell division by BA. This study was conducted to determine the phenological stage at which BA application provides maximum fruit weight relative to degree of cropload reduction. In all years, treatments were applied at a range of timings: petal fall (PF), 5-, 10-, or 15-mm king fruitlet diameter (KFD). For each thinner, the same concentration was used throughout the study. In 1994, only Accel® at 75 mg·L-1 was evaluated. In 1995, NAA (7.5 mg·L-1) + carbaryl (600 mg·L-1), Accel®, and a BA-only formulation were compared, but BA alone was applied only at PF, 10- and 15-mm KFD. In 1996, Accel® and NAA were compared with and without carbaryl at all timings. Most treatments reduced cropload and enhanced fruit weight. When data for all 3 years were combined, Accel® or BA increased cropload-adjusted fruit weight (CAFW) in 8 of 10 treatments made at 10- or 15-mm KFD, PF treatments never increased CAFW, and only one of four applications at 5-mm KFD increased CAFW. In contrast, NAA + carbaryl increased CAFW in four of four treatments applied at PF or 5-mm KFD, but in only one of four treatments at 10- or 15-mm KFD. Accel® was less effective than NAA in reducing fruit clusters to a single fruit per spur in most comparisons, either with or without carbaryl. Return bloom varied greatly across years, but was always influenced by application time and types of thinners. In 1994 and 1996, return bloom was closely related to cropload the previous year. Although return bloom was very low for most treatments in 1995, 10- and 15-mm KFD applications of NAA + carbaryl increased it three-fold in comparison with other treatments (NAA + carbaryl at PF or 5 mm or BA at 10-mm KFD) that had similar effects on cropload. Chemical names used: 6-benzyladenine (BA); naphthaleneacetic acid (NAA).

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Rosanne E. Franco and Susan S. Han

Senescence of excised Easter lily leaves is typically marked by a rise in respiration without a concomitant production of ethylene. Treating excised leaves with 500 mg·L-1 of gibberellic acid (GA3) or benzyladenine (BA) significantly delayed the onset of leaf yellowing, lowered the respiration rates by one-third to one-half, and markedly delayed the respiratory rise. Similar effects on respiration were detected in leaves treated with BA or GA3 before a 4-week period of cold storage and in leaves treated after chlorosis had initiated. Results of this study indicate that excised Easter lily leaves respond to the growth regulators with a significant decrease in respiration rate.

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D.C. Elfving and R.A. Cline

Benzyladenine (BA) applied postbloom at 125 and 250 mg·liter-1 thinned `Empire' apple (Malus domestica Borkh.) trees below commercial crop levels but thinned less than thidiazuron (THI) at 62 and 125 mg·liter-1. Ethephon (ETH) applied up to 250 mg·liter-1 reduced fruit set only slightly. When BA was tank-mixed with ETH, thinning was the same as with BA alone. Although THI thinned more, BA resulted in a larger increase in fruit weight. Seed development was nearly eliminated by THI, but was unaffected by either BA or ETH. Thinner effects on foliar nutrient concentrations were associated with changes in fruit load but not shoot growth. The effects of BA and ETH on fruit-flesh nutrient concentrations were similar to their effects on foliar nutrient concentrations. Although THI thinned strongly and produced large changes in foliar nutrient concentrations and seed count, THI resulted in virtually no changes in fruit-flesh nutrient concentrations. Chemical names used: N-(phenylmethyl)-1 H-purine-6-amine (benzyladenine); 2-chlorophosphonic acid (ethephon); N-phenyl-N'-1,2,3-thiadiazol-5-ylurea (thidiazuron).

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Susan S. Han

The development of greenhouse leaf yellowing in Easter lilies (Lilium longiflorum Thunb.) was significantly reduced by the application of growth regulator solutions containing gibberellins 4 and 7 (GA4+7) or benzyladenine (BA). Solutions containing BA alone significantly reduced leaf yellowing on plants caused by close spacing but were less effective than GA4+7. Application of BA alone, however, was not effective against root rot-induced leaf yellowing. When plants were treated with GA4+7 or BA + GA4+7 around the visible bud stage, nearly all of the leaves remained green until the end of the growing season. These growth regulators, however, increased the final height of the plants by 8–10 cm. The developmental rate and size of the flower buds, as well as the length of the pedicels were not affected by the growth regulator treatments. Thus application of these growth regulators greatly improved the quality of the leaves without compromising the quality and timing of the flowers. Chemical name used: N-(phenylmethyl)-1H-purine-6-amine (benzyladenine, BA).

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Mohamed F. Mohamed, Dermot P. Coyne and Paul E. Read

Plant regeneration has been achieved in two common bean lines from pedicel-derived callus that was separated from the explant and maintained through successive subcultures. Callus was induced either on B5 or MS medium containing 2% sucrose and enriched with 0.5 or 1.0 mg thidiaznron/liter alone or plus various concentrations of indoleacetic acid. The presence of 0.07 or 0.14 g ascorbic acid/liter in the maintenance media prolonged the maintenance time. Up to 40 shoot primordia were observed in 4-week-old cultures obtained from 40 to 50 mg callus tissues on shoot-induction medium containing 1-mg benzyladenine/liter. These shoot primordia developed two to five excisable shoots (>0.5 cm) on medium with 0.1-mg BA/liter. A histological study confirmed the organogenic nature of regeneration from the callus tissues. The R2 line from a selected variant plant showed stable expression of increased plant height and earlier maturity. Chemical names used: ascorbic acid, N- (phenylmethyl)-1H-pnrin-6-amine [benzyl-adenine, BA], 1H-indole-3-acetic acid (IAA), N- phenyl-N'-1,2,3-thiadiazol-5-ylurea [thidiazuron, TDZ].

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Jacob George, Harsh Pal Bais, G.A. Ravishankar and P. Manilal

Response surface methodology was utilized in statistical optimization of three quality factors (the number of multiple shoots, shoot length, and number of leaves) pertaining to regeneration of plantlets from leaf calli of Decalepis hamiltonii Wight. & Arn. (swallow root). The variables evaluated were the levels of sucrose, BA, and NAA each at two different concentrations. Response surfaces for shoot length and multiple shoot number were useful in achieving optimal levels of media constituents and in understanding their interactions, but response surfaces for number of leaves were not. The data indicate that sucrose, BA, and NAA levels may be manipulated to increase or decrease quality factors chosen. This approach may be useful in developing a micropropagation protocol for D. hamiltonii. Chemical names used: benzyladenine (BA); napthaleneacetic acid (NAA).