| Abstract: | In the leaf of rice (Oryza sativa L.) cultivar Yunnan purple rice, the anthocyanins with an obvious absorption peak at 530nm were distributed in the cells
of upper and lower epidermis, bulliform tissue and bristle. The maximal photosynthetic oxygen evolution rate and chlorophyll
content in flag leaves were 28% and 23%, respectively, more than the common green leaf rice cultivar Chijiaoruanzhan. Higher
chlorophyll content is probably one of the physiological adaptations for enhancing light harvesting capacity of the antenna
in photosystems in this cyanic leaves species. Upon the photooxidation of leaf segments mediated by methyl viologen in weak
light for 3 days, the distinct bleaching of anthocyanins in purple rice was associated with the reduction of scavenging ability
to DPPH · free radical ability and the increase in membrane leakage rate. But almost no changes in contents of flavonoids
and total phenolics were observed. Chlorophyll fluorescence parameters Fv/Fo, qP and ϕPSII decreased with the increase in NPQ and DES of xanthophylls cycle after photooxidation treatment. Green rice leaves showed
more decrease in DPPH · scavenging rate and more increase in cell membrane leakage rate but showed a trace of anthocyanins
during photooxidation. It is suggested that anthocyanin may be a beneficial and primary antioxidant in sun cyanic rice leaves
against oxidative stress induced by environmental adversity. And photooxidation could induce different changing patterns of
anthocyanins between the tested purple and green rice leaves. |
