Krol M, Gray GR, Hurry VM, Oquist G, Malek L, Huner NPA
Low-Temperature Stress and Photoperiod Affect an Increased Tolerance to Photoinhibition in Pinus-Banksiana Seedlings
Canadian Journal of Botany-Revue Canadienne De Botanique: 1995 73:1119-1127
The capacity to develop tolerance to photoinhibition of photosynthesis was assessed in jack pine seedlings (Pinus banksiana Lamb.). Photoinhibition induced at 5 degrees C in control jack pine seedlings grown at 20 degrees C was saturated above an irradiance of 1000 mu mol . m(-2). s(-1) but was detectable at an irradiance as low as 25 mu mol . m(-2). s(-1). However, 20 degrees C seedlings shifted to 5 degrees C were 2-fold more tolerant to photoinhibition than 20 degrees C unshifted control seedlings, as detected by either the light-dependent decrease in photochemical efficiency or the apparent quantum yield of O-2 evolution. The extent of this tolerance of photoinhibition was dependent upon time, photoperiod, and irradiance during exposure to the low-temperature shift. Furthermore, the tolerance of photoinhibition was correlated with anthocyanin accumulation in 20 degrees C grown seedlings shifted to 5 degrees C. In addition, seedlings shifted to 5 degrees C and an 8-h photoperiod exhibited a 2-fold higher yield of photosystem II electron transport, which was associated with an increased capacity to keep Q(A), the first stable quinone electron acceptor of photosystem II, oxidized at high irradiance. This was consistent with a 2-fold higher rate of photosynthesis on a chlorophyll basis. We propose that the combination of light attenuation by anthocyanin in the epidermis and enhanced rates of photosynthesis may, in part, account for the reduced sensitivity of jack pine to photoinhibition at low temperature.
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