As a major component of the plant primary cell wall, structure changes in pectin may affect the formation of the secondary cell wall and lead to serious consequences on plant growth and development. Pectin-modifying enzymes including pectate lyase-like proteins (PLLs) participate in the remodeling of pectin during organogenesis, especially during fruit ripening. In this study, we used Arabidopsis as a model system to identify critical PLL genes that are of particular importance for vascular development. Four PLL genes, named AtPLL15, AtPLL16, AtPLL19, and AtPLL26, were identified for xylem-specific expression. A knock-out T-DNA mutant of AtPLL16 displayed an increased amount of pectin, soluble sugar, and acid-soluble lignin (ASL). Interestingly, the atpll16 mutant exhibited an irregular xylem phenotype, accompanied by disordered xylem ray cells and an absence of interfascicular phloem fibers. The xylem fiber cell walls in the atpll16 mutant were thicker than those of the wild type. On the contrary, AtPLL16 overexpression resulted in expansion of the phloem and a dramatic change in the xylem-to-phloem ratios. Altogether, our data suggest that AtPLL16 as a pectate lyase plays an important role during vascular development in Arabidopsis.

This study reports on extensive and in-depth investigations into the morphological, photosynthetic, and physiological indices of 10 different types of Cypripedium plant introduced from Changbai Mountain. It is an important prerequisite for the ex situ conservation of Cypripedium plants to provide new insights into their photosynthesis. This result can not only promote the production of vegetative plants but also promote the production of plants with lots of flowers and the physiological characteristics of Cypripedium plants for promoting the artificial introduction and cultivation of wild resources. A critical comparison of the results showed that high light intensity is one of the causes of the reduction in photosynthesis in the samples. Cypripedium macranthum had the most morphological advantages, while Cypripedium guttatum, the smallest plant type, had the lowest plant morphogenesis. Photoinhibition began daily at 12:00 pm and reached a second peak at 14:00 pm in all 10 types. C. macranthum, Cypripedium ventricosum, and Cypripedium calceolus had greater photosynthetic capacity than the other types. Using principal component analysis, the order of photosynthetic physiological characteristics of the 10 Cypripedium plants was CCMY > CVPP > CCRY > CMPP > CVRR > CSPY > CMWW > CMLL > CMDD > CGWW. These results lay the groundwork for future research on Cypripedium resource distribution and artificial conservation.