1
Department of Bioenergy, School of Energy, Environment and Natural
resources, Madurai Kamaraj University, Madurai, India. 2 Laboratory for Electron Microscopy, Chemical Resource
Beneficiation (CRB), North-West University, Potchefstroom Campus,
Potchefstroom, South Africa.
Seedlings of bean plants (Phaseolus vulgaris L. Sel 9) were
grown for 2 weeks with half strength Hoagland solution containing 0 ppm
(deficient), 5 ppm (sufficient) and 50 ppm (excess) ZnSO4*7H2O.
Changes in photosynthetic pigments, soluble proteins, soluble starch,
photosystem (PSII) activities and thylakoid membrane proteins were
investigated. The degree of photoinhibition was determined by the
ratio of variable to maximum chlorophyll (Chl) fluorescence (Fv/Fm).
Photosynthetic pigments, soluble proteins and soluble starch decreased
significantly in Zn-deficient and Zn-excess leaves. Though the maximum
quantum yield of primary photochemistry (Fv/Fm), maximum variable
fluorescence (Fv) were significantly decreased to a greater extent in
Zn-excess leaves the restoration was excellent. The exogenous electron
donors, diphenylcarbazide (DPC) and NH2OH restored the loss
of PSII activity in Zn-deficient and Zn-excess leaves. A slight
degradation 33, 28-25, 23 and 17 kDa polypeptides were observed in the
Zn-deficient and Zn-excess leaves. Upon recovery from HI stress, the
Zn-excess leaves restored the 47, 33, and 28-25 kDa polypeptides.
Key
words: Bean; Chlorophyll fluorescence; High irradiance; PSII; Zinc
