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Nathan J. Jahnke, John M. Dole, and H. David Shew

( Gibson and Dole, 2006 ). At the wholesale level, sales of finished products produced from vegetative geranium cuttings are currently ≈$108.8 million ( U.S. Department of Agriculture, 2016 ). However, leaf yellowing is a common postshipping issue that can

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Susan S. Han

Postproduction leaf yellowing of Easter lily (Lilium longiflorum Thunb.) can be prevented by using growth regulators. Solutions containing benzyladenine (BA) reduced the percentage of yellow leaves in cold-stored plants, but solutions containing gibberellic acid (GA3) were not effective. Treatment with commercial products containing GA4+7 (Provide) or GA4+7 and BA (Promalin) nearly completely prevented the development of leaf yellowing. Concentrations as low as 25 mg·L-1 were effective. Leaf yellowing was prevented by growth regulators only on leaves that had been treated, indicating that the growth regulators were not mobilized in the plants. Growth regulator solutions halted further development of leaf yellowing when applied to plants that already had some chlorotic basal leaves. This result suggests that growth regulators need not be applied preventively. Treatment can be delayed until chlorotic lower leaves are first seen on plants. The striking effects of growth regulators in preventing leaf yellowing did not affect the development and opening of flower buds.

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Susan S. Han

The marked effects of growth regulators such as GA3 and BA in delaying leaf yellowing on excised leaves of Easter lilies decreased when studies were conducted on intact plants in a simulated interior environment. Solutions containing benzyladenine (BA) delayed the development of leaf yellowing in cold-stored plants, but solutions containing gibberellic acid (GA3) were not effective when applied to plants at the puffy bud stage and evaluated in a 22.6 ± 0.2°C room illuminated 12 h/day with 11.2 ± 0.1 μmol·s–1·m–2 cool-white fluorescent lamp. Treatment with commercial products containing GA4+7 (Provide) or GA4+7 and BA (Promalin) nearly completely prevent the development of leaf yellowing. Concentrations as low as 25 mg·L–1 were effective. The prevention of leaf yellowing by growth regulators was only effective on leaves that had been treated, indicating that mobilization of the growth regulators in the plants did not occur. Growth regulator solutions halted further development of leaf yellowing when applied to plants that already possessed some chlorotic, basal leaves. The striking effects of growth regulators on preventing leaf yellowing did not affect the development and opening of the flower buds and is a practical solution for the prevention of post-production leaf yellowing in Easter lilies.

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Anil P. Rartwala, William B. Miller, P. Allen Hammer, and Terri Kirk

The possible factors contributing to leaf yellowing during the postharvest phase of Easter lilies (Lilium longiflorum Thunb.) were investigated. Higher levels of growth retardants, forcing under negative DIF conditions, cold storage (4.0°C) at the `puffy bud' stage and shipping stress were shown to increase leaf yellowing during postharvest holding. Concentrations of soluble carbohydrates and starch under inductive and non-inductive conditions were determined to investigate the correlation of it to leaf yellowing. Lilies grown under negative DIP had lower concentrations of leaf, stem and flower soluble carbohydrates and starch compared to plants grown under positive DIF. Investigation of diurnal fluctuations of leaf carbohydrates revealed low carbohydrate levels in negative DIP-forced plants at all times during the diurnal cycle. Supplemental light (50-60 μmo1 m-2s-1) during cold storage increased leaf carbohydrate levels. Higher levels of bud abortion and reduced flower longevity were also observed under conditions inductive of leaf yellowing.

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Susan S. Han

The development of postharvest leaf yellowing affects the quality of cut Oriental and Asiatic lilies. Without cold storage, lower leaves began to turn yellow ≈1 week after placing them in an interior environment. The development of leaf yellowing continued to progress upward until the vase life was over with >25% of the leaves chlorotic. Cold storage of cut lilies worsened this leaf disorder. The longer the duration of cold storage, the sooner the development of leaf yellowing and the higher the percentage of leaves that were chlorotic. Spraying leaves with a solution containing 25 mg·L-1 each of BA and GA4+7 significantly reduced cold-stored induced leaf yellowing in both Oriental and Asiatic lily. While the growth regulator treatment completely prevented leaf yellowing of cold-stored Asiatic lilies, its effectiveness in Oriental lilies diminished with the duration of cold storage. Timing of the growth regulator application was not critical, as there were no differences in leaf yellowing when the growth regulator solution was sprayed before or after the cold storage. The concentration of the growth regulators was inversely related to the development of leaf yellowing and concentrations <5 mg·L-1 each of BA and GA4+7 were not effective. Alternative means of applying the growth regulators were evaluated, including the addition of the growth regulators to the preservative solution or as a pulsed treatment. Both methods completely prevented leaf yellowing but also induced bud abortion. For practical application, spraying the growth regulator solution on the leaves prior to or after cold storage would significantly improve postharvest quality of the cut lilies.

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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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Peter R. Hicklenton

Leaf yellowing of Alstroemeria hybrida L. `Rio' and `Jacqueline', as measured by sphere spectrocolorimetry, was significantly delayed in vase life studies when the ends of cut stems were immersed in solutions of BAP or GA3 immediately following harvest. When BAP or GA3 was used alone at 50 mg·liter-1, foliage color and color intensity did not diminish during 14 days of storage in tap water. BAP and GA3 also showed interaction effects on leaf color, but little was gained by using combinations of chemicals. Chemical names used: 6N-benzylaminopurine (BAP); gibberellin (GA3).

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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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Anil P. Ranwala and William B. Miller

Our previous research has demonstrated preventive effects of foliar sprays of growth regulators containing GA4+7 (ProVide or Promalin) on cold storage-induced leaf yellowing and abscission in `Stargazer' hybrid lilies. Further research was conducted to investigate the effective concentrations of Promalin and appropriate timing of promalin sprays. Lilies at “puffy bud” stage were sprayed with promalin at concentrations of 10, 25, 50 or 100 ppm (each GA4+7 and BA) just before placing them at 4 °C for 2 weeks in darkness. Promalin concentrations of 25 ppm or above completely prevented cold storage-induced leaf yellowing occurring during the poststorage evaluation phase in a simulated consumer environment, whereas 10 ppm sprays only partially prevented it. Foliar spray of Promalin (100 ppm each GA4+7 and BA) just before storage at 4 °C for 2 weeks was compared with spraying 2 or 4 weeks before cold storage. While spraying 2 weeks before storage prevented leaf yellowing to the same extent observed in plants sprayed just before cold storage, spraying 4 weeks before storage had very little preventive effect on leaf yellowing. To investigate the effectiveness of promalin sprays with different cold storage durations, puffy-bud stage plants were stored at 4 °C for 1, 2, 3, 4, or 5 weeks in darkness with or without promalin sprays (100 ppm each GA4+7 and BA) before storage. Longer cold storage durations increased the severity of leaf yellowing occurring during poststorage phase. Although promalin was able to prevent leaf yellowing completely up to 2 weeks of cold storage, beyond 3 weeks of cold-storage, effectiveness of promalin diminished with no apparent preventive effect on plants stored for 5 weeks.

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Duane W. Greene

combination of ABA and BA as a thinning spray was used by Greene et al. (2011) on apples not only to improve thinner response, but also counteract the leaf yellowing and leaf abscission ( Greene et al., 2011 ) effect caused by the ABA on some apple cultivars