Flower bud growth and ovule longevity of plum (Prunus domestics L.) cultivars Italian and Brooks and the effects of fall-applied ethephon and of temperature were studied. Fresh and dry weights of terminal flower buds were measured at l-week intervals from 50 days to 1 day before bloom in 1988. Buds were also analyzed for N, P, K, Ca, and B. After bloom, ovule longevity was determined using a fluorescence method after staining with aniline blue. Ovule longevity was determined in 1990 using shoots excised at full bloom from untreated and ethephon-treated trees of both cultivars and held in growth chambers for 18 days at 5, 10, 15, or 20C. `Brooks' flower buds showed a higher accumulation of fresh and dry weight than `Italian', and ethephon reduced bud weights in both cultivars. Ethephon did not affect mineral content of flower buds of `Brooks', but `Italian' flower buds contained a higher concentration of Ca and a lower concentration of P when treated with ethephon. Boron content was higher in the ethephon-treated buds of `Italian' trees on some sampling dates. Ovule longevity was higher for `Brooks' than for `Italian' in both years. Ethephon treatment delayed ovule senescence in `Italian' flowers, but had little or no effect on `Brooks' flowers. Increasing temperatures induced faster ovule senescence in both cultivars. Chemical name used. 2-chloroethylphosphonic acid (ethephon).
Yerko M. Morenol, Anita Nina Miller-Azarenko, and William Potts
Kathleen G. Haynes, William E. Potts, Jesse L. Chittams, and Diane L. Fleck
For the yellow-flesh fresh market, potato (Solanum tuberosum L.) varieties with intense yellow flesh are desired. Twenty-five yellow-flesh clones, including 24 U.S. Dept. of Agriculture (USDA) selections and the check variety `Yukon Gold', were evaluated for tuber yellow-flesh color, as measured by a reflectance colorimeter, and for individual tuber weight in replicated field trials in Presque Isle, Maine, in 1991 and 1992. There were significant differences among clones for yellow-flesh intensity. Yellow-flesh intensity in two USDA selections was significantly less than in `Yukon Gold'. In four USDA selections, yellow-flesh intensity was significantly greater than in `Yukon Gold'. In general, there was an inverse relationship between tuber weight and yellow-flesh intensity. Subsamples of tubers whose weight fell between the 10 to 90, 25 to 75, 35 to 65, and 40 to 60 percentile were compared to the full sample. There was good agreement between the 10 to 90 and 25 to 75 percentile subsample and the full sample regarding the average yellow-flesh intensity and in the consistency of pairwise comparisons between individual selections and `Yukon Gold'. For determining yellow-flesh intensity, the 25 to 75 percentile subsample was as informative as the full sample.
John R. Teasdale, Aref A. Abdul-Baki, and William J.E. Potts
Dry weight and leaf area of tomato (Lycopersicon esculentum Mill.) plants grown on raised beds with black polyethylene (BP) or hairy vetch (Vicia villosa Roth) (HV) mulches were measured at weekly intervals during 1993 and 1994. Leaf area and foliage, fruit, and total weight of tomato plants grown in BP were greater early in the season, but less later in the season than plants grown in HV. The relative growth rate of tomatoes in HV was higher throughout most of each year than that in BP. There was little difference between treatments in unit leaf rate (rate of weight gain per unit leaf area). The growth rate of fruit per unit of tomato foliage was greater in BP than HV, whereas the leaf area to weight ratio was greater in HV than BP. These results suggest that tomatoes grown in BP produce greater early yield because of greater early foliage growth and greater partitioning to fruit than HV. However, tomatoes grown in HV eventually outgrow and outyield those in BP because of greater partitioning to and maintenance of leaf area throughout the season.