Drought-induced changes in photosynthesis of young cowpea plants

K. Uzunova, Z. Zlatev
Abstract. Laboratory experiments were conducted to study the effect of soil drought on photosynthesis of young cowpea plants (Vigna unguiculata L.) – cv. Lagoa and cv. 1183. Drought conditions were imposed on 2-week-old plants by withholding water for 10 days. It was established that drought seriously inhibits net photosynthetic rate (A) and transpiration rate (E). Minimal (F ) fluorescence increases and maximal (F ) and variable (F ) fluorescence decrease. In light 0 m v adapted leaves a significant decrease in quantum yield (Y), photochemical quenching (qP) and electron transport rate (ETR) of PSII occurred. In conclusion, it is considered that the photosynthetic apparatus of cv. Lagoa is more tolerant and of cv. 1183 more sensitive to drought.


Changes in chlorophyll fluorescence and leaf gas exchange of durum wheat under low positive temperatures

Z. Zlatev, T. Kolev

Abstract. Changes of functional activity of the photosynthetic apparatus of four durum wheat cultivars under low positive temperature stress were studied. Parameters of chlorophyll fluorescence in dark-adapted and light-adapted leaves were analyzed, as well as leaf gas exchange. The applied stress induced an increase in F accompanied by a decrease in F in the second leaf of the studied cultivars. At the end of the stress period plant of cv. Reamur and cv. Exodur limit 0 m to greater extent transpiration intensity and stomatal conductance, this leads, together with significantly reduced activity of PS2, to substantial inhibition of net photosynthetic rate (P ). It is established, that photosynthetic apparatus of cultivars Karur and Pescadou is more tolerant and photosynthetic apparatus of N cultivars Reamur and Exodur is more sensitive to low positive temperature stress.