Photosynthetic activity of developing leaves of Zea mays is less affected by heat stress than that of developed leaves

Abstract

Various physiological and biochemical characters of a leafthe slightly affected P n of the developing leaf was associated change with stages of its ontogeny. It is likely that the with the almost unchanged photochemical efficiency of photophotosynthetic functions of leaves of different ontogeny have system II (F v /F m ) and the quantum yield of photosystem II different levels of heat tolerance. This study was initiated to electron transport. The chlorophylls a and b were degraded by analyze the photosynthetic heat tolerance of fully-developed, heat stress; the degradation was pronounced in the developed nearly-developed (more than 2/3 expanded) and developing leaves. As a result of heat stress, the antheraxanthin and zeaxanthin of the xanthophyll cycle accumulated in both the (10-12 cm visible) leaves of two maize genotypes, F223 and nearly-developed and developed leaves but not in the develop-F250. The results indicate that the photosynthetic CO 2 assimilation rate (P n ) of developing leaves was less affected by heat ing leaves. Injury to the plasma membrane due to heat stress stress (42°C in the dark for 90 min) than that of developed was much less severe in developing leaves than that in the leaves. The impaired P n recovered within 24 h in the develop-developed leaves. From the physiological characters which we determined it would appear that the P n functions of the ing leaves, while the P n of developed and nearly-developed developing leaves are more resistant to heat stress than those leaves did not reach the non-stress level, even after 72 h. The of nearly-developed and developed leaves. P n of the developed leaves of genotype F250 was less affected by heat stress than that of genotype F223. After heat stress,

Seasonal variations and acclimation potential of the thermostability of photochemistry in four Mediterranean conifers

“…The seasonal time course was tightly related to that of ambient temperature, confirming earlier findings [2,33]. This seasonal effect may be combined with a needle age effect; in maize, younger leaves displayed a larger thermostability than older ones [20]. Interestingly, values recorded after summer were higher than during spring despite similar thermal regimes before needle collection.…”

Impacts of Heat Stress on Wheat: A Critical Review

“…Overall these damages may result in reduced photosynthetic rate, impaired translocation of assimilates and reduced carbon gain that ultimately lead to distorted growth and abnormal reproduction [33]. Heat-stress also affects the sensitivity of pigmentation in wheat, maize, and on photosystem II (PS-II) functions in wheat that in turn has lethal impact on seedling growth and leaf development [34][35][36]. Exposure to higher temperature results in reduced yield and production of inferior quality of cereals [37].…”

Yield and physiological responses of mungbean Vigna radita (L.) Wilczek genotypes to high temperature at reproductive stage

“…The physicochemical properties as well as the functional organization of thylakoid membrane are changed reversibly or irreversibly by high temperature (Berry et al, 1980;Karim et al, 1999). PSII is the most heat-sensitive component of the photosynthetic (Berry et al, 1980;Mamedov et al, 1993).…”