EVIDENCE OF UVB EFFECT ON THE PHOTOCONVERSION OF ACTIVE PROTOCHLOROPHYLLIDES INTO CHLOROPHYLLIDES IN ETIOLATED BARLEY LEAVES

摘要

The effect of ultraviolet B (UVB) radiation on photoconversion of active protochlorophyllides (PChlide(638,650)) into chlorophyllide(672) (Chl(ide)(672)) in etiolated barley leaves, triggered by low and strong light intensity, was investigated. After etiolated barley leaves have been exposed to UVB radiation, conversion of photoactive PChlide induced by saturating flash or by continuous low photosynthetically active radiation was measured by a spectrograph equipped with an intensified diode-array system. Here, for the first time, we are reporting a strong inhibitory effect of UVB radiation on chlorophyllide(684) (Chlide(684)) formation triggered by high-intensity flash. The formation of Chlide(684) was inhibited by 85% when etiolated barley leaves were exposed to 2 h of UVB radiation. However, during regeneration in the dark, the extent of PChlide(650) phototransformation gradually returns to the control value, For the same UVB irradiation time, the inhibitory effect on the Shibata shift was not so evident because the efficiency of the Shibata shift was decreased by only 15%, However, Chl(ide)(672) formation was accelerated when etiolated barley leaves were exposed to low-intensity continuous illumination supplemented with UVB radiation. [References: 30]