Photosystem 2 (PS2)-driven electron transfer was studied in primary leaves of barley (Hordeum vulgare L.) seedlings grown under various photon fluxes (0.3-170.0 μmol m-2 s-1) of blue (BR) or red (RR) radiation using modulated chlorophyll fluorescence. The Fv/Fm ratio was 0.78-0.79 in leaves of all radiation variants, except in seedlings grown under BR or RR of 0.3 μmol m-2 s-1. The extent of the photochemical phase of the polyphasic Fv rise induced by very strong "white light" was similar in leaves of all radiation treatments. Neither radiation quality nor photon flux under plant cultivation influenced the amount of non QB-transferring centres of PS2 except in leaves of seedlings grown under BR of 0.3 μmol m-2 s-1, in which the amount of such centres increased threefold. Both BR and RR stimulated the development of photochemically competent PS2 at photon fluxes as low as 3 μmol m-2 s-1. Three exponential components with highly different half times were distinguished in the kinetics of Fv dark decay. This indicates different pathways of electron transfer from QA-, the reduced primary acceptor of PS2, to other acceptors. Relative magnitudes of the individual decay components did not depend on the radiation quality or the photon flux during plant cultivation. Significant differences were found, however, between plants grown under BR or RR in the rate of the middle and fast components of Fv dark decay, which showed 1.5-times faster intersystem linear electron transport in BR-grown leaves. and E. A. Egorova, N. G. Bukhov.
Stomatal responses of attached bean (Phaseolus vulgaris L.) leaves to changing spectral composition ("white" - WL., blue - BL, or red - RL radiation), air humidity (100 % or about 4 % RH), and water potential of the root medium (close to 0 or -1.2 MPa) were determined by air flow porometer. Opening of stomata always increased under BL and decreased under RL. In response to decline in air humidity, leaf conductance showed transient increase before it reached lowered steady state. BL enhanced and RL diminished this response. and S. Maleszewski ... [et al.].