Shengqun Liu

Low solar radiation is an important factor affecting maize root growth and development. Roots have an anchoring function, and their important components are cellulose and lignin. Here, shade experiments were conducted using shade nets with 50% light transmittance (L₅₀). The experiment was conducted in 2021 and 2022 using the ‘Xianyu 335’ maize variety under two nitrogen conditions (N₁ = 180 kg ha⁻¹ and N₂ = 240 kg ha⁻¹) to investigate the effect of shading on the structural carbohydrate content of maize nodal roots. The results showed that light had a highly significant effect on cellulose and lignin contents. Compared with normal light (L₁₀₀), the cellulose content significantly decreased by 10.36%–13.87% and the lignin content significantly decreased by 12.96%–18.68% under shading (L₅₀). Shading decreased the sucrose and soluble sugar contents and the cellulose and lignin‐related enzyme activities. The cellulose and lignin contents were significantly positively correlated with the sucrose content. The cellulose content at the silking (R1) stage was significantly positively correlated with the soluble sugar content and sucrose synthase (SS) and sucrose phosphate synthase activities at the 15th leaf (V15) stage; the lignin content at R1 was significantly positively correlated with the soluble sugar content and SS, acid invertase, tyrosine ammonia‐lyase, cinnamyl alcohol dehydrogenase, polyphenol oxidase and peroxidase activities at V15. Genes related to cellulose synthesis, including sucrose synthase (SS), cellulose synthase (CESA), cellulose synthase‐interactive protein 1 (CSI1), Chitinase‐Like1 (CTL1) and STELLO2 (STL2), were downregulated under shading, as were the lignin synthesis‐related phenylalanine/tyrosine ammonia‐lyase (PTAL), 4‐coumarate‐CoA ligase (4CL) and peroxidase (POD) genes. Auxin and jasmonic acid were significantly affected by light and decreased under shading, thereby reducing cellulose and lignin synthesis. These findings provide theoretical support for the development of appropriate maize cultivation practices under reduced solar radiation.

The transgenerational effect of elevated atmospheric CO₂ concentration (e[CO₂]) on low temperature response in wheat is still little investigated, through the interaction of e[CO₂], and low‐temperature stress has been reported in a single generation. Here, the low temperature‐induced modifications of chloroplast ultrastructure and carbohydrate metabolism in wheat after four generations continuously grown under ambient CO₂ concentration (a[CO₂]) and e[CO₂] (2014–2018) were investigated. The results indicated that the transgenerational exposure to e[CO₂] increased the number of grana lamellae and the amounts of osmiophilic lipid droplets, attenuating the negative effect of low temperature on chloroplast ultrastructure. The transgenerational e[CO₂] enhanced the activities of antioxidant enzymes (i.e. SOD, POD and CAT) and concentrations of osmotic substances (i.e. proline and soluble sugar), which alleviated the low temperature‐induced oxidative damage to the chloroplast ultrastructure. In addition, transgenerational exposure of wheat to e[CO₂] increased activities of vacInv and cwInv, while decreased fructokinase activity, which affected the sucrose metabolism in wheat leaf. These findings elucidated that transgenerational exposure to e[CO₂] could improve low temperature tolerance of winter wheat, which provide novel insights to the response of wheat to future climate change.

Row direction and plant spacing influence crop senescence. An experiment was conducted to analyze the effect of row direction and plant spacing on the husk leaf senescence. Physiological indicators related to husk leaf senescence at days after silking (DAS) 12, 22, and 40 were investigated under two row directions (east to west and south to north, abbreviated as EW and SN, respectively) and three plant patterns (single rows spaced at 65 cm, 40 cm twin rows spaced at 90 cm between the paired rows of narrow–wide rows, and 40 cm twin rows spaced at 160 cm between the paired rows of narrow–wide rows, abbreviated as SR, WN1, and WN2, respectively). Row direction affects the chlorophyll content and dehydration rate according to our results. Superoxide dismutase activity at DAS 22, catalase (CAT) activity at DS, and abscisic acid (ABA) concentrations at DAS 12, 22, and 40 were significantly affected by plant spacing. The CAT activities of WN1 and WN2 were significantly higher than those of SR, and WN2 had a lower ABA concentration than WN1 and SR. Our results suggest that row direction from SN and plant spacing from WN1 and WN2 were the suitable conditions for delaying the senescence of husk leaves of maize in the experimental site.