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Grafting desirable scion on stress-tolerant rootstocks provides an opportunity to improve the cryotolerance of scion. Genic male sterile (GMS) lines of plant could be used as sterile line and maintainer in breeding, and they have the conspicuous characteristics that the fertility of which is easy to regain but hard to maintain by sexual reproduction. In order to maintain the fertility of GMS cotton by means of its perennial growth on the basis of frostless winters in Nanning, Guangxi autonomous region, GMS line A4 was grafted onto 7 cryotolerant rootstocks (F118, F697, F098, F112, F113, P098 and P113), and the cryotolerance and the overwintering survivorship of scions were investigated. In consequence, when compared with control (self-grafted A4), the relative conductivity of the grafted plants in shoot bark was reduced (8.80%), the content of soluble sugar, soluble protein and free proline were higher, 25.00, 1.55, 3.46%, respectively; the overwintering survival rate and the height of regeneration bud under field condition of grafted plants were higher, 10.44, 15.75%, respectively; the order of the grafted plants based on the average subordinate function value of overwintering survivorship was A4/F113>A4/F118>A4/F098>A4/F697>A4/F112>A4/P098>A4/P113>A4/A4(CK); the correlation analyses indicated that the physiological parameters of cryotolerance could be used for forecasting the overwintering survivorship, and the relative conductivity could be chosen as the first physiological parameter for forecasting cryotolerance or overwintering survivorship. The results indicate that the cryotolerance and the overwintering survivorship of GMS cotton could be improved by grafting, and F113 appeared to be a valuable rootstock. [ABSTRACT FROM AUTHOR]

Coronatine [COR] is a novel type of plant growth regulator with similarities in structure and property to jasmonate. The objective of this study was to examine the relationship between increased root vitality induced by 10nM COR and reactive oxygen species scavenging under potassium (K)-replete (2.5mM) and K-deficient (0.05mM) conditions in hydroponic cultured cotton seedlings. K-replete and K-deficient conditions increased root vitality by 2.7- and 3.5-fold, respectively. COR treatment significantly decreased lipid peroxidation in cotton seedlings determined by reduction in MDA levels. These results suggest that COR improves the functioning of both enzymatic and non-enzymatic antioxidant systems. Under K-replete and K-deficient conditions, COR significantly increased the activities of antioxidant enzymes SOD (only for K-repletion), CAT, GPX, and APX comparing; COR also significantly increased DPPH-radical scavenging activity. However, COR led to 1.6- and 1.7-fold increases in superoxide anion (O2•-) concentrations, and 5.7- and 2.1-fold increases in hydrogen peroxide (H2O2) levels, respectively. Additionally, COR intensified the DAB staining of H2O2 and the NBT staining of O2•-. Therefore, our results reveal that COR-induced ROS accumulation stimulates the activities of most antioxidant enzymes but does not induce oxidative stress in cotton roots. [ABSTRACT FROM AUTHOR]

Abstract: Agricultural crops experience diverse mechanical stimuli, which may affect their growth and development. This study was conducted to investigate the effects of mechanical stresses caused by hanging labels from the flower petioles (HLFP) on plant shape and cotton yields in four cotton varieties: CCRI 41, DP 99B, CCRC 21, and BAI 1. HLFP significantly reduced plant height by between 7.8% and 36.5% in all four lines and also significantly reduced the number of fruiting positions per plant in the CCRI 41, DP 99B and CCRC 21 lines. However, the number of fruiting positions in BAI 1 was unaffected. HLFP also significantly reduced the boll weight for all four cultivars and the seed cotton yields for CCRI 41, DP 99B and BAI 1. Conversely, it significantly increased the seed cotton yield for CCRC 21 by 11.2%. HLFP treatment did not significantly affect the boll count in the fruiting branches of the 1st and 2nd layers in any variety, but did significantly reduce those on the 3rd and 4th fruiting branch layers for CCRI 41 and DP 99B. Similar trends were observed for the number of bolls per FP. In general, HLFP reduced plant height and boll weight. However, the lines responded differently to HLFP treatment in terms of their total numbers of fruiting positions, boll numbers, seed cotton yields, etc. Our results also suggested that HFLP responses might be delayed for some agronomy traits of some cotton genotypes, and that hanging labels from early-opening flowers might influence the properties related with those that opened later on. [ABSTRACT FROM AUTHOR]