EFFECTS OF LIGHT, MECHANICAL STRESSES, EXOGENOUS ABSCISIC ACID, AND/OR OUTDOOR EXPOSURE ON GROWTH, WATER RELATIONS, AND ENDOGENOUS ABSCISIC ACID CONTENT OF EGGPLANT (ACCLIMATION, ABA, HARDENING-OFF, PLANT CONDITIONING)
Abstract
Initial exposure of greenhouse-grown herbaceous seedlings to outdoor summer conditions results in temporary stunting of growth prior to acclimation to the new environment. Eggplant (Solanum melongena L. var. esculentum 'Burpee's Black Beauty') seedlings grown in the greenhouse were subjected to various treatments in an attempt to mimic acclimation or to condition seedlings to outdoor conditions. Pretreatment of seedlings with supplemental photosynthetically-active radiation improved growth of eggplants subsequently transferred outdoors relative to that of plants grown under 55% shade or no shade in the greenhouse. Protection of eggplant seedlings from solar ultraviolet-B radiation (UV-B, 280-315 nm) after transfer outdoors from a greenhouse resulted in greater leaf area than for UV-B-exposed seedlings, but no change in leaf or shoot dry weight. Exposure of eggplant to UV-B provided by sunlamps in the greenhouse also decreased leaf expansion and leaf and shoot dry weight gain when measured after 5 days of treatment. However, after 12 days of UV-B treatment there was no difference in leaf or shoot dry weight relative to control plants, indicating that the UV-B-treated plants had acclimated to the stress. Eggplant and soybean (Glycine max (L.) Merr. 'Wells II') seedlings were assigned to a greenhouse or a windless or windy outdoor environment. Plants within each environment received either periodic seismic or thigmic treatments, or were left undisturbed. Productivity and dimensional growth parameters generally were reduced more by mechanical stress in the wind-protected environments than in the outdoor windy environment. Greenhouse-grown eggplant were treated with mechanical stress or exogenous abscisic acid (ABA) prior to 4 or 5 days of outdoor exposure. Treatments generally did not decrease growth responses relative to controls during a 3-day conditioning period in the greenhouse. Treatments increased specific leaf chlorophyll in the greenhouse. Mechanical stress had no effect on endogenous ABA levels in leaves. Seismic stress decreased leaf water potential. Outdoor exposure of untreated eggplants altered water status, decreased relative growth rate and specific leaf chlorophyll content, and increased leaf ABA content relative to greenhouse control plants.
Degree
Ph.D.
Subject Area
Neurology
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