The aim of ťhis study was to clarify whether there are generál differences between the woody and herbaceous plants in their responses to a single non-lethal freezing stress, when measured under comparable conditions. Activity of net photosynthesis (^N33)» th® curves of versus photosynthetic photon fluence density and versus intercellular partial pressure of CO2, and ratio of variable to maximal fluorescence (F^Fm) were measured at optimal temperatures in the leaves of six woody and six herbaceous plant species prior to frost-hardening, after frost-hardening at low positive temperatures and after a single over-night freezing stress (-10 ®C, 12 h) of the shoots. Recovery of at 20/15 “C was also followed. There were no generál differences between woody and herbaceous plants in their photosynthetic responses to freezing stress. In most plants, Pn33 was strongly reduced after freezing mainly due to the disturbances in fimctioning of the chloroplasts, but it recovered within a few days. However, of some herbaceous plants (Cochlearia, one cultivar of spinách) was insensitive to non-lethal freezing. Furthermore, stomatal opening of a few herbaceous plants (Cochlearia, Valerianella) was disturbed after freezing without any sign of an impairment in fimctioning of the chloroplasts.
In the present study, the physiological efficiencies of 181 mini-core peanut accessions (genotypes) were evaluated according to variability in their physiological performance in the field during summer (2012). Genotypes were categorized into groups of high, medium, and low physiological activity. Thirty-four genotypes showed high net photosynthetic rate (PN > 33 μmol m-2 s-1), 28 genotypes exhibited high stomatal conductance (gs > 0.54 mmol m-2 s-1), 33 genotypes manifested high transpiration rate (E > 11.8 mmol m-2 s-1), 30 genotypes performed with high water-use efficiency (WUE > 3.8), 30 genotypes reached high chlorophyll SPAD values (SCMR > 40), and 35 genotypes showed high maximum quantum yield of PSII (Fv/Fm > 0.86). In addition, few genotypes showed high values for multiple physiological traits. A total of 54 genotypes exhibited higher values in two, 20 genotypes showed a high value in three, and in eight genotypes, high values occurred in four different physiological traits. Interestingly, only two genotypes, NRCG 14493 and 14507, showed high values for five different traits. Positive correlation was observed between gs and PN, E, and gs, and between PN and Fv/Fm, while WUE and E showed a negative correlation. The genotypes with high PN, gs, and WUE coupled with high SCMR and Fv/Fm could be used in peanut crop improvement programme for yield enhancement as well as stress tolerance., A. L. Singh, R. N. Nakar, K. Chakraborty, K. A. Kalariya., and Obsahuje bibliografii