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With twelve peanut cultivars grown under artificial water control, the drought resistance related physiological and biochemical traits and the drought resistance mechanism of peanut leaves were studied. Two water treatments were designed, that were 50% and 70% of the soil relative water content of the 0-80 cm soil layer, respectively, at pod-setting stage. The results showed that the twelve peanut cultivars could be grouped into three different resistance levels based on their yield drought resistance coefficient. The A596, Shanhua 11 and Rugaoxiyangsheng were grouped as cultivars with high resistance, while Huayu 20, Nongda 818, Haihua 1, Shanhua 9 and 79266 with moderate resistance, and the ICG6848, Baisha 1016, Hua 17 and Penglaiyiwohou with weak resistance. The mechanism of high drought resistance in peanut cultivars of A596, Shanhua 11 and Rugaoxiyangsheng were due to more powerful antioxidant capacity, higher activity of photosystem II (PS II) and photosynthetic rate (Pn). By contrast, the moderate resistant cultivars Haihua 1 had stronger antioxidant protection capability, and the Shanhua 9 had much higher PS II activity. The Pn, stomatal limitation value (Ls), maximal photochemical efficiency of PS II (Fv/Fm), photochemical quenching coefficient (q(p)), content of malondialdehyde (MDA), relative electric conductivity and superoxide dismutase (SOD) activity of leaves were very significantly correlated with the drought resistance coefficient. Therefore, they were important indicative traits for the drought resistance at pod-setting stage of peanuts. These traits could be evaluated under normal irrigation condition except that the SOD activity should be identified under drought stress. Based on this study, we proposed that Shanhua 11 and 79266 could serve as standard cultivars of high drought resistance and weak drought resistance, respectively. Shanhua 11 could also serve as a standard cultivar for identification of leaf drought resistance traits in peanut.

One of the critical enzymes involved in vitamin E biosynthesis in plants is 2-methyl-6-phytyl-1,4-benzoquinol methyltransferase (MPBQ MT). The full-length VTE3 cDNA (designated rVTE3-1 and -2) encoding MPBQ MT and the full-length DNA of VTE3 (designated gVTE3-1 and -2) were isolated from cultivated peanuts (Arachis hypogaea). The full-length DNA of VTE3 (designated gVTE3-A and -B) was isolated from the wild groundnut species A. duranensis (A-genome) and A. ipaënsis (B-genome), and polymorphism analysis of VTE3 was performed. The results demonstrated that rVTE3-1 and -2 both have a DNA sequence that is 1059 bp long and encodes 351 amino acids; the homology of the 2 amino acid sequences was 98.6%. The gVTE3-1 of cultivated Fenghua 2 peanut samples was 2710 bp long, with 3 introns located at 44-163, 772-1295, and 1603-2437 bp, and the Fenghua 2 gVTE3-2 was 2706 bp long, with 3 introns located at 44-169, 778-1291, and 1599-2433 bp. The homology for gVTE3-1 and -2 across 13 cultivated peanut samples was 99.9 and 100%, respectively. gVTE3-1 and -2 were from A- and B-genome, respectively, with 96.6% homology between the 2 sequences. The present study demonstrated that abundant polymorphisms were present in the VTE3 genes from different genomes. Additionally, polymorphisms were observed in the gVTE3-1 alleles of the 13 cultivars and wild A. duranensis species but not in the gVTE3-2 alleles of the 13 cultivars and wild A. ipaënsis species.

To investigate the effects of shading and light recovery on the photosynthetic characteristics of peanut seedlings leaves, different shading treatments including no shading, 27% shading, 43% shading, and 77% shading were performed with black sunshade net at the seedling stage of two peanut cultivars Fenghua 1 and Fenghua 2, with related parameters determined. It was shown that with the increase of shading degree, the leaf chlorophyll content, actual PSII photochemical efficiency under irradiance (phi(PS II)), and maximum PS II photochemical efficiency (Fv/Fm) of test cultivars increased, while the Chl a/b ratio and photosynthetic rate (Pn) decreased. On the first day after light recovery, the Pn and stomatal conductance (Gs) decreased while the intercellular CO2 concentration (Ci) increased with increasing shading degree when measured under high light, but the Pn increased and the Gs and Ci decreased with increasing shading degree when measured under low light. The ratio of Pn measured under low light to that measured under high light increased significantly. With increasing shading degree, the light compensation point, light saturation point, CO2 compensation point, CO2 saturation point, and carboxylation efficiency decreased, while the apparent quantum yield increased. After the removal of shading, the Pn, phi(PS II), and Fv/Fm under natural light decreased immediately, but increased gradually 3-5 days after. 15 days after light recovery, the Pn, phi(PS II) and Fv/Fm in treatment 27% shading recovered to the level of no shading. As for the other treatments, the restored extent differed with shading degree and test variety. In the same treatments, the leaf chlorophyll content, Pn and phi(PS II) of Fenghua 1 were higher than those of Fenghua 2. The results demonstrated that shading at seedling stage improved the capabilities of test varieties in using low light, but reduced the capabilities in using high light.