Physiological Consequences of Structural and Ultra-structural Changes Induced by Zn Stress in<I> Phaseolus vulgaris</I>. I. Growth and Photosynthetic Apparatus
Title:
Physiological Consequences of Structural and Ultra-structural Changes Induced by Zn Stress in<I> Phaseolus vulgaris</I>. I. Growth and Photosynthetic Apparatus
Author:
Wedad A. Kasim
Appeared in:
International journal of botany
Paging:
Volume 3 (2007) nr. 1 pages 15-22
Year:
2007
Contents:
Seeds of <I>Phaseolus vulgaris </I>L. cv. Limburgs vroege were sown in peat moss supplemented with ZnSO<SUB>4</SUB> (600 mg kg<SUP>-1</SUP>) and irrigated with distilled water for 14 days. Ten growth criteria and 12 anatomical measurements in the shoot (hypocotyl, epicotyl and primary leaves) were reduced by ZnSO<SUB>4</SUB> but remained unaffected in the root, despite greater accumulation of Zn<SUP>2+</SUP> in roots. Shoots and roots of <I>P. vulgaris</I> seedlings seemed to show differential sensitivity to Zn stress. Reduction in shoot growth criteria seemed to result from a decrease in parenchyma cell size and diameters of metaxylem vessels in the leaf midrib. Scanning Electron Microscope (SEM) revealed the presence of compacted grana with reduced thylakoids in chloroplasts, which might have contributed to the recorded loss of chl-a, chl-b and carotenoids. In primary leaves, occlusion of intercellular spaces and impregnation of middle lamellae with Zn seemed to hamper substomatal CO<SUB>2</SUB> diffusion, while increased K<SUP>+</SUP>-leakage indicated Zn-induced injury to cell membranes. The Zn-induced 6-fold increase in stomatal deformation, reduction in frequency of normal stomata, photosynthetic pigments and substomatal CO<SUB>2</SUB> concentration in primary leaves, coupled with reductions in cell enlargement, transport capacity of xylem in the shoot, might have resulted collectively in the measured reduction in the photosynthetic rate which would in turn lead to the observed reductions in shoot growth criteria.
Publisher:
Asian Network for Scientific Information (provided by DOAJ)
Journal description