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Abstract In this study, we investigated the function of OsAAI1 in yield and drought tolerance by constructing overexpression line OE-OsAAI1 and mutant line osaai1. Bioinformatics analysis showed that the AAI gene-OsAAI1- belongs to the HPS_like subfamily of the AAI_LTSS superfamily, and OsAAI1 was localized in the nucleus. The expression of OsAAI1 was significantly induced by ABA and drought stress. OsAAI1 overexpression (OE19) significantly increased, and gene mutant (osaai1-1) repressed plant height, primary root length, lateral root number, grain size and yield in rice. Moreover, physiological and biochemical analyses showed that osaai1 was sensitive to drought stress, while OE19 enhanced the drought tolerance in rice. DAB and NBT staining revealed that under drought treatment, osaai1 accumulated a large amount of ROS compared with the wild type, while OE19 accumulated the least, and CAT, APX, GPX, GR activities were higher in OE19 and lower in osaai1, suggesting that OE19 improves rice tolerance to drought stress by enhancing ROS scavenging ability. OE19 also induce the expression of ABA-mediated regulatory pathway genes and enhance accumulation of ABA content in rice seedling. Predictably, OE19 displayed enhanced sensitivity to ABA, and ROS accumulation was significantly higher than in wild type and osaai1 under 3 µM ABA treatment. Thus, these results suggest that OsAAI1 is a positive regulator of rice yield and drought tolerance dependent on the ABA-mediated regulatory and ROS scavenging pathway.

Based on the Glivenko-Cantelli theorem and Weibull distribution functions, the fatigue life of foam concrete with different sisal fibre volume fraction (0–0.3% vol.) was performed. When the two-parameter Weibull function was selected, a linear regression analysis showed that the fatigue life had high correlation between the independent and dependent variables (correlation coefficients above 0.75). But the three-parameter Weibull analysis gave more accurate results (correlation coefficients above 0.90). Then, the corresponding Weibull probability density function distributions of the fatigue lives were compared. Based on the parameters obtained, the fatigue lives of foam concrete with different survival probabilities were analyzed and compared with results taken from the literature. Finally, for specific survival probabilities, the fatigue limit and fatigue life of foam concrete under specified stress level were predicted.

To investigate the relationship between mineral elements and plum gummosis disease, Prunus salicina Lindl. trees with four grades of gummosis were used as the experimental materials. The contents of N, P, K, Ca, Mg, B, Fe, Mn, Zn and Cu in the branches and leaves were measured, and the correlation between mineral elements and gummosis was systemically analyzed through multiple comparisons, binary logistic regression analysis, and ordinal logistic regression analysis. In addition, the effects of prevention and control of the necessary mineral elements on the gummosis disease of P. salicina were verified after a fertilization experiment. The results indicate that the contents of nitrogen and manganese positively correlate with the occurrence of gummosis. In contrast, the contents of calcium and boron significantly negatively correlate with the occurrence of gummosis. A fertilization experiment facilitated the discovery that the control of nitrogen, as well as the increased application of boron and calcium fertilizers, contributed to the prevention and control on gummosis disease in P. salicina.

Expansins are unique plant cell wall proteins that are involved in cell wall modifications underlying many plant developmental processes. In this work, we investigated the possible biological role of the root-specific α-expansin gene OsEXPA8 in rice growth and development by generating transgenic plants. Overexpression of OsEXPA8 in rice plants yielded pleiotropic phenotypes of improved root system architecture (longer primary roots, more lateral roots and root hairs), increased plant height, enhanced leaf number and enlarged leaf size. Further study indicated that the average cell length in both leaf and root vascular bundles was enhanced, and the cell growth in suspension cultures was increased, which revealed the cellular basis for OsEXPA8-mediated rice plant growth acceleration. Expansins are thought to be a key factor required for cell enlargement and wall loosening. Atomic force microscopy (AFM) technology revealed that average wall stiffness values for 35S::OsEXPA8 transgenic suspension-cultured cells decreased over six-fold compared to wild-type counterparts during different growth phases. Moreover, a prominent change in the wall polymer composition of suspension cells was observed, and Fourier-transform infrared (FTIR) spectra revealed a relative increase in the ratios of the polysaccharide/lignin content in cell wall compositions of OsEXPA8 overexpressors. These results support a role for expansins in cell expansion and plant growth.

Expansins are cell-wall-loosening proteins known to be involved in a wide range of physical processes during plant development. OsEXPA3, a rice a-expansin gene, was found to be preferentially expressed in the root and highly induced by NaCl, while suppressed by nitrate (N) and phosphate (Pi) starvation. Repression of OsEXPA3 expression by RNA interference (RNAi) in rice (Oryza sativa L.) severely impaired the growth of the root system. A significant reduction in the primary root length and lateral root density was observed in 1-wk-old OsEXPA3-RNAi lines at seedling stage, and the total size and density of the root system was clearly decreased in 1-mo-old plants. Besides, the root hair of RNAi seedlings was clearly shorter than that of wildtype plants. Moreover, RNAi plants exhibited clearly inhibited growth, which is mostly attributed to the poorer root system architecture. Further study indicated that the cell length of root vascular bundles and cell growth in suspension cultures in OsEXPA3-RNAi lines decreased significantly, which revealed the cellular basis for OsEXPA3-mediated rice root growth. Further, the cell-wall mechanical properties of suspension cells probed by atomic force microscopy (AFM) showed that repression of OsEXPA3 led to a significant increase in cell-wall stiffness, and cell-wall polymer compositions revealed by Fourier transform infrared (FTIR) spectra were also strongly changed. Taken together, the results suggest that OsEXPA3 is required for root system development in rice and involved in mediating root growth by mediating cell-wall loosening. [ABSTRACT FROM AUTHOR]