Spectral and dose dependence of light-induced ion flux responses from maize [Zea mays] leaves and their involvement in leaf expansion growth
2007
Zivanovic, B.D.(University of Tasmania (Australia)) | Cuin, T.A. | Shabala, S.
Two types of segments (intact leaf tissue and isolated mesophyll tissue respectively) were isolated from basal (still growing) and tip (non-growing) maize leaf regions. The leaf segments were exposed to different light qualities (blue or red light) and quantities, and net fluxes of Ksup(+), Casup(2+) and Hsup(+) were measured non-invasively using ion-selective vibrating microelectrodes (the MIFE technique). A clear dose dependency of all ion flux responses on both red (RL) and blue (BL) light fluence rate was found. We provide evidence that light-induced Ksup(+) flux kinetics are different between growing and non-growing tissues and attribute this difference to the direct involvement of RL-induced Ksup(+) flux in turgor-driven leaf expansion growth controlled by the epidermis, as well as to the charge-balancing role of Ksup(+) in the leaf mesophyll. Generally, BL was much more efficient in stimulating Ksup(+) uptake in the growing basal region compared with RL. We also show a much stronger influence of RL on Casup(2+) fluxes in the basal region compared with BL, which argues in favor of the importance of RL in Casup(2+) signaling during leaf growth.
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