The Relationship Among Photoinhibition, Photooxidation and Early Aging at a Late Development Stage in Different Varieties with High Yield

Using six high yield varieties from different ecological districts in China the parameters of Chl fluorescence, the performance of membrane lipid peroxidation and the reduction of Chl content in flag leaf under natural condition at the later developmental stages (from heading stage to mature stage). The results showed that Fv/Fm , decreased gradually, the excessive light energy led to the accumulation of active oxygen O2-, H2O2 and the product of membrane-lipid peroxidation, MDA, which resulted in the reduction of Chl content and early aging due to photooxidation during the course of senescence of flag leaf. This phenomenon varied obviously in rice varieties. When comparina japonica tolerant to photooxidation, Fv/Fm in indica shanyou 63 susceptible to photoxidation decreased significantly. An increase of active oxygen and a sharp drop of Chl content, resulted in 'yellowish' early aging and influenced filling and setting of rice grain. The mechanism on early aging in indica was related to light and temperature conditions in filling stages. On a fine day (above 251), PS Ⅱ reaction center exhibited a dynamic change on revisable inactivation. Under strong midday light, PS Ⅱ function in indica exhibited obvious down-regulation and photoinhibition; Under strong light with low temperature, PS Ⅱ resulted in photodamage, showing early aging, which were related to the degradation of PSⅡ - D1 Protein and the inhibition of the endogenous protecting system such as Xanthophyll cycle and the enzymes of scavenging active oxygen. The results suggested that for a view of high-yield breeding, on the basis of a good type-plant, giving consideration to the utilization of heterosis and resistance to early aging, selecting japonica or a sterile line with japonice genotype as maternal was a breeding strategy worthy of being paid more attention.

Green Tea Polyphenols Prevent Early Vascular Aging Induced by High-Fat Diet via Promoting Autophagy in Young Adult Rats

Objective Epidemiology studies indicate that green tea polyphenols(GTP)perform a protective effect on cardiovascular diseases,but the underlying mechanisms are complex.The present study aimed to investigate the effect of GTP on high-fat diets(HFD)induced-early vascular aging.Methods Six-week young adult Wistar rats were fed with standard chow or HFD in the presence and absence of GTP(200 mg/kg body weight)for 18 weeks.In vitro experiment,human umbilical vascular endothelial cells(HUVECs)were treated with palmitic acid(PA)and GTP.Results The results showed that GTP alleviated the disorganized arterial wall and the increased intima-media thickness induced by HFD.In addition,the vascular oxidative injury was suppressed following GTP treatment.Furthermore,GTP elevated the ratio of LC3-II/LC3-I and suppressed expression of p62/SQSTM1,and restored SIRT3 expression in the aorta of HFD rats.Consistently,in cultured HUVECs,GTP inhibited cell senescence indicated by SA-β-gal and promoted endothelial autophagy compared with the PA treatment group.The activity of SIRT3 was specifically inhibited by 3-TYP,and the protective effect of GTP was consequently abolished.Conclusion The findings indicated that GTP protected against early vascular senescence in young HFD rats via ameliorating oxidative injury and promoting autophagy which was partially regulated by the SIRT3 pathway.