Long-Term Chilling of Young Tomato Plants under Low Light. III. Leaf Development as Reflected by Photosynthesis Parameters |
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Authors: | Brggemann, Wolfgang Dauborn, Babette |
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Affiliation: | Department of Ecological Plant Physiology, Heinrich-Heine-University, Universittsstr.1 D-W-4000 Dsseldorf 1, Federal Republic of Germany |
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Abstract: | Young tomato plants were exposed to two weeks of chilling undernon-photoinhibiting or mild photoinhibiting conditions. Thedevelopment of the leaves was studied under chilling and controlconditions by measuring several physiological parameters. Agradual decrease of the efficiency of the photosynthetic apparatuswith maturation and ageing occurred in unchilled plants. Thiswas reflected by gradual changes in CO2-saturated photosynthesisand protein and rubisco contents. Except for senescing leaves,a correlation close to 1 : 1 was observed between maximum rubiscoactivity and CO2-saturated photosynthesis. Chlorophyll (Chl)contents and photochemical chlorophyll fluorescence quenchingshowed strong decreases only in the last phase of senescencein the oldest leaves. In plants chilled under non-photoinhibitingconditions (10C, 100150 µE m2 s1or 6C, 3050 µE m-2 s1), a similar patternof ageing was observed, and no indications were found for aninduction of protein or rubisco degradation by chilling. Sincethese plants stopped growing in the cold, they revealed lowertotal photosynthetic capacities than unchilled plants of thesame size. When the chilling conditions were mildly photoinhibitory(6C, 100150 µE m2 s1), a much strongerdepression of rubisco activity and photosynthetic capacity wasfound in all leaves, which was partly reversible in the youngones. This decrease in CO2fixation capacity, in turn, led toa higher susceptibility of the chilled plants to photoinhibitionat 20C. It is concluded that the decrease of both photosyntheticcapacity and growth after long-term chilling in tomato is aconsequence of the preceeding ageing and senescing of the leavesduring chilling, in contrast to chilling-tolerant species withthe ability for acclimation to low temperatures. (Received April 26, 1993; Accepted September 7, 1993) |
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