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【Objective】 Maize is a main staple crop cultivated in central and Northern China but it requires irrigation at certain stages during its growth. In this paper, we present the findings of an experimental study on the effect of irrigation amount on photosynthesis and dry matter accumulation of the crop during its tasseling-silking stage. 【Method】 The field experiment was conducted in the long-term experiment established in 2018 at the experimental base of the academy of agricultural and animal husbandry sciences of Inner Mongolia Autonomous Region. The experiment compared six irrigation amounts: 315 m3/hm2 (W1), 645 m3/hm2 (W2), 945 m3/hm2 (W3), 1 275 m3/hm2 (W4), and 1 605 m3/hm2 (W5); the control was rain-fed (W0). During the experiment, we measured photosynthetic characteristics and dry matter accumulation of the crop in each treatment. The photosynthetic characteristics and its correlation with dry matter accumulation were calculated by fitting the response curve parameters to a non-right-angle hyperbolic model. 【Result】 The leaf SPAD in W3 was lower only than that in W4 in 2019, but in 2020 it increased by 3.96%, 5.12%, 11.10%, 12.64% and 19.90%, respectively, compared with that in W4, W2, W1, W5 and W0. In 2019 and 2020, the average daily net photosynthetic rate was the highest in W3, while in 2019, the dry weights of stems, leaves and ears in W3 were the second highest among all treatments. In 2020, the physiological indexes of the crop in W3 were higher than that in other treatments. There was no significant difference in leaf photosynthesis between W3, W4 and W5. 【Conclusion】 In central and western regions of Inner Mongolia, when the total rainfall during growing season of maize exceeded 365 mm, irrigating 945 m3/hm2 of water can effectively improve photosynthetic efficiency of the maize during its tasseling-silking stage, promote dry matter accumulation and increase grain yield.

SUMMARY: Xylan is one of the major hemicelluloses in plant cell walls and its xylosyl backbone is often decorated at O‐2 with glucuronic acid (GlcA) and/or methylglucuronic acid (MeGlcA) residues. The GlcA/MeGlcA side chains may be further substituted with 2‐O‐arabinopyranose (Arap) or 2‐O‐galactopyranose (Gal) residues in some plant species, but the enzymes responsible for these substitutions remain unknown. During our endeavor to investigate the enzymatic activities of Arabidopsis MUR3‐clade members of the GT47 glycosyltransferase family, we found that one of them was able to transfer Arap from UDP‐Arap onto O‐2 of GlcA side chains of xylan, and thus it was named xylan 2‐O‐arabinopyranosyltransferase 1 (AtXAPT1). The function of AtXAPT1 was verified in planta by its T‐DNA knockout mutation showing a loss of the Arap substitution on xylan GlcA side chains. Further biochemical characterization of XAPT close homologs from other plant species demonstrated that while the poplar ones had the same catalytic activity as AtXAPT1, those from Eucalyptus, lemon‐scented gum, sea apple, 'Ohi'a lehua, duckweed and purple yam were capable of catalyzing both 2‐O‐Arap and 2‐O‐Gal substitutions of xylan GlcA side chains albeit with differential activities. Sequential reactions with XAPTs and glucuronoxylan methyltransferase 3 (GXM3) showed that XAPTs acted poorly on MeGlcA side chains, whereas GXM3 could efficiently methylate arabinosylated or galactosylated GlcA side chains of xylan. Furthermore, molecular docking and site‐directed mutagenesis analyses of Eucalyptus XAPT1 revealed critical roles of several amino acid residues at the putative active site in its activity. Together, these findings establish that XAPTs residing in the MUR3 clade of family GT47 are responsible for 2‐O‐arabinopyranosylation and 2‐O‐galactosylation of GlcA side chains of xylan. Significance Statement: Xylan is one of the major hemicelluloses in plant cell walls and its GlcA side chains may be further substituted with 2‐O‐Arap or 2‐O‐Gal residues. We have uncovered the functions of a subgroup of MUR3‐clade GT47 members in catalyzing the transfer of 2‐O‐Arap and/or 2‐O‐Gal onto GlcA side chains of xylan, which expands our understanding of glycosyltransferases involved in xylan substitutions. [ABSTRACT FROM AUTHOR]

Plant cell walls are largely composed of polysaccharide polymers, including cellulose, hemicelluloses (xyloglucan, xylan, mannan, and mixed-linkage β-1,3/1,4-glucan), and pectins. Among these cell wall polysaccharides, xyloglucan, xylan, mannan, and pectins are often O-acetylated, and polysaccharide O-acetylation plays important roles in cell wall assembly and disease resistance. Genetic and biochemical analyses have implicated the involvement of three groups of proteins in plant cell wall polysaccharide O-acetylation: trichome birefringence-like (TBL)/domain of unknown function 231 (DUF231), reduced wall acetylation (RWA), and altered xyloglucan 9 (AXY9). Although the exact roles of RWAs and AXY9 are yet to be identified, members of the TBL/DUF231 family have been found to be O-acetyltransferases responsible for the O-acetylation of xyloglucan, xylan, mannan, and pectins. Here, we provide a comprehensive overview of the occurrence of O-acetylated cell wall polysaccharides, the biochemical properties, structural features, and evolution of cell wall polysaccharide O-acetyltransferases, and the potential biotechnological applications of manipulations of cell wall polysaccharide acetylation. Further in-depth studies of the biochemical mechanisms of cell wall polysaccharide O-acetylation will not only enrich our understanding of cell wall biology, but also have important implications in engineering plants with increased disease resistance and reduced recalcitrance for biofuel production. [ABSTRACT FROM AUTHOR]

This study prepared resistant starch (RS) from waxy corn starch and normal corn starch and analyzed the effects of its molecular and microstructural characteristics on RS content. The RS content of waxy corn resistant starch (RS-WCS) was highest at 57.8%, whereas that of normal corn resistant starch (RS-NCS) was 41.46%. The short-chain amylose contents of RS-WCS and RS-NCS were 47.08% and 37.24%, respectively, proportional to their RS content. Additionally, RS content positively correlated with crystallinity, short-range order degree, and degree of polymerization (DP), exceeding 25. Electron microscopic images, before and after enzymolysis, revealed that RS-WCS was hydrolyzed from the surface to the center by pancreatic α-amylase, while RS-NCS underwent simultaneous hydrolysis at the surface and center. These results indicate that the higher RS content in RS-WCS, compared to RS-NCS, is attributable to the synergistic effects of molecular structure and microstructure. [ABSTRACT FROM AUTHOR]

Here we introduce a metal‐free, catalytic and enantioselective strategy from α,β‐unsaturated 2‐acyl imidazoles to the chiral phosphorous 2‐acyl imidazoles. Interestingly, this methodology was catalyzed by the classical and commercial oxazaborolidine under mild conditions. This strategy features a wide range of substrates scope with good yields and excellent enantioselectivities. The possible mechanism further suggests the key of this reaction through the cleavage of diarylphosphine oxides using Frustrated Lewis Pairs theory. [ABSTRACT FROM AUTHOR]