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  • Author or Editor: K. E. Cushman x
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Chlorosis and necrotic spotting develop on expanding leaves of particular cultivars of potato (Solanum tuberosum L.) when grown under constant light and temperature conditions. Plantlets of a constant-light sensitive cultivar, Kennebec, were planted into peat:vermiculite and established at 18C for 10 d under a 12 h light: 12 h dark photoperiod. Plants were then exposed to constant light and sprayed with 1 ml of either 0.5 mM silver thiosulfate (STS), an ethylene-action inhibitor, or water (as a control) every 2 days. Specific `target' leaflets, 5-10 mm in length at the beginning of the constant-light period, were harvested on days 5-9 of constant light, during injury development, and placed in bags made of Teflon film for IO-15 minutes to collect ethylene. Ethylene release and necrotic spotting increased as days of constant light increased for both water and STS-treated leaves, though STS-treated leaves produced slightly less ethylene and significantly less necrotic spotting than water-treated leaves. Ethylene release was correlated with extent of necrotic spotting. STS-treated plants exhibited greater dry weight and leaf area then water-treated plants. The results indicate that ethylene is not only produced by injured leaf tissue but, in addition, that ethylene may have a role in the development of constant-light injury symptoms.

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Viola tricolor seed were exposed to aerated solutions of water or 300 or 400 mM NaCl for 0, 2, 4, 6, or 8 days. After priming treatments, seed were air dried, placed on moist filter paper in petri dishes, and set in dark growth chambers at 18 or 30°C for germination. priming for 6 days in water increased germination of `Crystal Bowl Yellow' seed from 80 to 88% when germinated at 30 °. Untreated seed germination was 92% at 18°. Priming for 6 days in 300 mM NaCl improved germination of `Majestic Giant Blue' seed from 57 to 76% when germinated at 30°. Untreated seed germination was 80% at 18°. These data indicate that seed priming could be used to improve summer germination of a cool season annual. Priming increased germination at the higher than optimum temperature (30°) to levels similar to that for the optimum temperature (18°). However, the best priming solution depended on the cultivar.

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Several experiments were conducted in commercial tomato (Solanum lycopersicum) plantings during the 2004–05 and 2005–06 seasons in Immokalee, FL, to understand types of plant damage and potential yield reductions caused by hurricanes. Expt. 1 involved ‘Florida 91’ tomato seedlings damaged during 2004 by hurricane Frances, 15 days after transplanting (DAT). Individual plants were rated and categorized as best, good, or fair, 34 DAT according to plant size and vigor/severity of injury. Ten plants from each category were removed with roots intact, and dry weights were recorded. During 2005, 23 DAT or 8 days after hurricane Wilma, Expt. 2 was conducted to compare rescued and replanted ‘Soraya’ tomato seedlings. Rescued seedlings were left in place after the hurricane and others were removed and replaced with new transplants of the same variety. Expt. 3 (‘Florida 47’) and 4 (‘BHN 586’) involved the contrast of two yield seasons without a hurricane (2004–05) and with hurricane Wilma (2005–06) to estimate the effect of the hurricane damage on tomato 65 and 45 DAT. Fruit was counted, graded by size, and weighed for each experiment from 10 plants/plot. Injury caused by hurricane winds was most evident in Expt. 1 mostly in stem damage below the soil surface showed callous tissue at the site of injury due to plants being whipped around in the planting hole. Plants rated “best” showed greater plant and root dry weight, stem diameter below the injury point, and higher yield of extra large and total marketable fruit at first harvest than plants rated good or fair. Total marketable yields from rescued plants in Expt. 2 were double than that from replanted plants, and fruit matured 20 days earlier for rescued plants indicating that plants injured by Wilma recovered quickly. Hurricane-damaged crops during 2005–06 in Expts. 3 and 4 yielded 60% lower than that of undamaged crops during 2004–05. In the extra large size category, the yields were reduced between 34% and 12% from the previous season. However, hurricane-damaged loss of yield in the extra large category was offset by increased yield in the medium category. It appears that hurricane-damaged plants, when young, were capable of full recovery and normal yields, whereas hurricane-damaged plants, when older at the time injury occurred, were not able to fully recover and eventually produced only half the normal yield.

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