Search Results
Abstract
The salt tolerances of a cultivated tomato (Lycopersicon esculentum L. cv. Heinz 1350) and three wild species [L. cheesmanii (Hook) C.H. Mull, L. peruvianum (L.), and L. pennellii (Cornell) D’Arcy] were determined in both sand and solution cultures. Curvilinear and two-piece linear methods were used to obtain response curves for fresh and dry weights of shoots. In solution cultures containing 0, 50, 100, and 150 mM added salt composed of 1:1 molar ratio of NaCl and CaCl2, ‘Heinz 1350’ was as salt-tolerant as any of the wild species. On the basis of relative decreases in vegetative dry weight, ecotype 1400 of L. cheesmanii was more sensitive to salt than ecotype 1401. After 4 weeks growth in sand cultures irrigated with nutrient solutions containing 0, 12.5, 25, 50, 75, and 100 mM added salts (5:1 molar ratios of NaCl and CaCl2), L. pennellii had higher relative salt tolerance than the other species. After 14 weeks, the cultivated species and L. pennellii were more sensitive at low salinity than the other two species. However, relative yield decreases with increasing salinity were not significantly different between the cultivated tomato and the 1401 ecotype of L. cheesmanii at higher salt concentrations. L. peruvianum and L. pennellii accumulated less leaf Cl- and more leaf Na+ than the other species. Significant differences in the partitioning of ions between mature and developing leaves were found for all species. The physiological mechanisms involved in tolerance at moderate salinities may differ from those required for survival at high salinity.
Blossom-end rot (BER) is one of the major physiological disorders of green-house bell pepper (Capsicum annuum L.). The objective of the present work was to study the effects of the solution N concentration and N-NO3: N-NH4 ratio on fruit yield and the incidence of BER and other fruit-quality traits of greenhouse-grown bell pepper in a Mediterranean climate. Three experiments were conducted: Expt. 1 included five total N concentrations (0.25 to 14 mmol·L-1, with a constant N-NO3: N-NH4 ratio of 4); Expt. 2 included five treatments of different NO3: NH4 molar ratios (0.25 to 4, with a constant N concentration of 7 mmol·L-1); and Expt. 3 included three treatments of different NO3: NH4 molar ratios (1.0, 3.0 and 9.0, with a constant N concentration of 7 mmol·L-1). Plants were grown in an aero-hydroponics system in Expts. 1 and 2 and in tuff medium in Expt. 3, in greenhouses in Israel. The optimal values of N concentration for total fruit yield and for high fruit quality (marketable) were 9.3 and 8.3 mmol·L-1, respectively. The total and high-quality fruit yields both increased with increasing N-NO3: N-NH4 ratio in the range studied. The total and high-quality fruit yields both decreased sharply as the NH4 concentration in the solution increased above 2 mmol·L-1. The increase in the NH4 concentration in the solution is the main cause of the suppression of Ca concentration in the leaves and fruits and the increased incidence of BER. The occurrence of flat fruits also increased with increasing NH4 concentration in the solution.