Short-term responses of photosynthetic membrane lipids and photochemical efficiency in plants of Phaseolus vulgaris and Vigna unguiculata submitted to high irradiance

Abstract

Primary leaves of young plants of common bean (Phaseolus vulgaris cv. Carioca and Negro Huasteco) and cowpea (Vigna unguiculata Walp cv. Epace 10) were exposed to high irradiance (HI) of 2 000 µmol m -2 s -1 for 10, 20, and 30 min. The initial fluorescence (F 0 ) was nearly constant in response to HI in each genotype except for Carioca. A distinct reduction of maximum fluorescence (F m ) was clearly observed in stressed genotypes of beans after 20 min followed by a slight recovery for the longer stress times. In common bean, the maximum quantum yield (F v /F m ) was reduced slowly from 10 to 30 min of HI. In cowpea, only a slight reduction of F v /F m was observed at 20 min followed by recovery to normal values at 30 min. HI resulted in changes in the photochemical (q P ) and non-photochemical (q N ) quenching in both species, but to a different extent. In cowpea plants, more efficiency in the use of the absorbed energy under photoinhibitory conditions was related to increase in q P and decrease in q N . In addition, lipid peroxidation changed significantly in common bean genotypes with an evident increase after 20 min of HI. Hence the photosynthetic apparatus of cowpea was more tolerant to HI than that of common bean and the integrity of cowpea cell membranes was apparently maintained under HI.

Wheat cultivars differing in heat tolerance show a differential response to monocarpic senescence under high-temperature stress and the involvement of serine proteases

“…Prior to measurement, the leaves were dark-adapted for 10 min, with the help of leaf clips (provided with the instrument). The ratio of F v /F m , termed as maximum efficiency of PSII photochemistry and nonphotochemical quenching (q N ) were assessed following Ferreira et al (2007) with some modifications. The procedure was as follows: The initial fluorescence (F 0 ) obtained with modulated low irradiance (<0.1 µmol m -2 s -1 ), maximum fluorescence (F m ) determined with a pulse of saturating irradiance (3000 μmol m -2 s -1 ) with duration of 0.3 s, and maximum quantum yield of PSII; F v /F m = (F m -F 0 )/F m .…”

Photosynthetic characteristics involved in adaptability to Karst soil and alien invasion of paper mulberry (Broussonetia papyrifera (L.) Vent.) in comparison with mulberry (Morus alba L.)

“…These quenching coefficients were automatically calculated with the MINI-PAM. Electron transport rate was estimated as ETR = ΔF/F´m×PAR×0.5×0.84, where ΔF/F´m is the effective quantum yield of irradiated sample (variable fluorescence/effective maximum fluorescence), and PAR is photosynthetically active radiation (Ferreira et al 2007). q P , q N , and ETR were measured in response to different PAR consisting of 11 consecutive periods of "actinic light" (0,41,76,134,205,249,298,371,456,581, and 726 μmol m −2 s −1 ).…”

EFFECTS OF Ca AND P NUTRIENT LEVELS ON THE GROWTH OF N-FERTILIZED AND RHIZOBIUM-NODULATED PHASEOLUS VULGARIS L. SUBJECTED TO TWO CONTRASTING TROPICAL SOLAR RADIATION REGIMES AND SPRAYED WITH PROPYL GALLATE

“…However, a detailed review of the literature revealed limited data on the physiology of common bean under HI. Studies conducted in temperature-controlled growth chambers where N-fertilized (+N) plants were under low PPFD <300 μmol m −2 s −1 before being subjected to HI>1000 μmol m −2 s −1 for short periods of time (Ferreira et al , 2007; Lambreva et al , 2005; Marschner and Cakmak, 1989). Overall information indicates limited antioxidant capacity and basal thermotolerance in +N common bean for minimising oxidative damage caused by HI/HT (Guidi et al , 2000; Shainberg et al , 1999; Tsai and Hsu, 2009).…”