Two teak (Tectona grandis L.f.) phenotypes differing in their leaf length/breadth ratios were subjected to water stress by withholding water supply for three weeks. Growth rates of whole plants, developing leaves (1st and 2nd from shoot apices), and 2nd and 3rd internodes were higher in broad leaved (BL) phenotype than in narrow leaved (NL) phenotype before and after imposing water stress treatment. However, the effect of water stress on these parameters was higher in the BL phenotype than in the NL one. Diurnal course of net photosynthetic rate (PN) of 3rd or 4th leaves from shoot apices measured under well-watered conditions was higher for the NL than BL phenotype. PN, stomatal conductance (gs), and transpiration rate (E) in both phenotypes were negatively affected by water stress and their decline under water stress was significantly higher in the BL than NL plants. and G. Rajendrudu, C. V. Naidu, K. Mallikarjuna.
Effects of selective reagents of amino groups (fluorescamine, Fc) and thiol [5,5'-dithio-bis(2-nitrobenzoic) acid, DTNB] groups on the diaphorase activity of spinach ferredoxin:NADP+ oxidoreductase (FNR, E.C 1.18.1.2) in the presence of dibromothymoquinone (DBMIB) as an electron acceptor were studied. The incubation of FNR with 250 μM Fc in the time range from 0 to 120 min led to the gradual decrease of FNR activity according to biphasic kinetics. At the initial phase the activity (defined as the rate of NADPH oxidation) decreased about 4-time faster than at the subsequent second slower phase. Incubation of FNR simultaneously with Fc and DBMIB for more than 20 min caused restoration of the activity to about 80 % of the control. The inhibitory effect of Fc on the FNR-catalysed DBMIB reduction had non-competitive character. Incubation of FNR with DTNB led also to a gradual decrease of the enzyme activity, which reached about 45 % of the control after 2 h of incubation. Thus neither amino nor thiol groups in the FNR molecule are involved directly in the DBMIB reduction. However, the presence of DBMIB in the incubation medium influenced the inhibitory pattern of Fc and DTNB, and this suggests that DBMIB modified the conformational state of the FNR molecule. and J. Grzyb, M. Bojko, S. Więckowski.
Cadmium (Cd) treatments caused an inhibition in the net photosynthetic rate (PN) of peanut (Arachis hypogaea) plants, due to the reduction of stomatal conductance (gs) and photosynthetic pigment contents, as well as the alteration in leaf structure. The decrease of the transpiration rate and gs might result from the Cd-induced xerophyte anatomic features of leaves (i.e. thick lamina, upper epidermis, palisade mesophyll, high palisade to spongy thickness ratio, as well as abundant and small stomata). The decline of PN was independent of the impairment in photosystem 2. and G. R. Shi, Q. S. Cai.