ABIOTIC FACTORS AFFECTING PLANT PHYSIOLOGY AND FRUIT YIELD AND PHYSIOLOGICAL DISORDERS IN BELL PEPPER AND TOMATO

Abiotic factors such as light, irrigation, and calcium nutrition strongly influence bell pepper and tomato production. Effects of shade level and irrigation level on bell pepper plant physiology and fruit attributes were investigated in Tifton, GA. Additionally, the effect of irrigation level and calcium on plant and fruit growth and blossom-end rot (BER) development were evaluated in a BER-resistant and a BER-susceptible tomato accession. In bell pepper, shading improved leaf water status, favoring plant growth, increasing fruit yield and decreasing fruit disorders. Photosynthetically active radiation, leaf net photosynthesis, electron transport rate, transpiration and water use efficiency decreased and intercellular CO2 and photosystem II (PSII) efficiency increased as the shade level increased. A CO2 response (A/Cc) curve revealed that maximum rate of carboxylation, triose phosphate utilization, mesophyll conductance and rate of electron transport were similar in plants grown at 30% shade and open field. Light response (A/I) curve showed that the highest gross and net photosynthesis were obtained from 30% shade; light compensation point decreased as shade level increased. Increased irrigation level generally increased plant growth in bell pepper. Marketable fruit yield at 67% ETc was similar to that at 100% ETc. Sunscald incidence decreased as the irrigation level increased though blossom-end rot incidence remained unaffected. In tomato, BER symptoms were found only in the BER-susceptible accession. Application of calcium reduced BER incidence by 5%-11%. Plant height and top dry weight increased and chlorophyll content decreased in the BER-susceptible accession only under well-irrigated conditions. Fruit diameter and height of the BER-susceptible accession were higher than those of the BER-resistant accession. In conclusion, bell pepper had optimal plant growth and function and optimal fruit yield and quality when grown at 30% shade level. A suboptimal irrigation level (67% ETc) was sufficient to produce acceptable marketable fruit yield. In tomato, plant and fruit growth of BER-resistant differed from those of BER-susceptible accession; whether these differences influenced fruit Ca2+ availability and BER development, requires further investigations.

INDEX WORDS: Water potential, Photosynthesis, Sunscald, A/Cc curve, A/I

Curve, Fruit growth, BER resistant, NON-EXPRESSOR OF

PATHOGENESIS RELATED 1, PATHOGENESIS RELATED 1