In recent years, global climate change has continued to intensify, with extreme weather events occurring frequently, posing increasingly severe challenges to agricultural ecosystems. Late spring coldness, as a typical low-temperature meteorological disaster in spring, often occurs suddenly during the key growth stages of crops such as the germination period, flowering period or the growth of seedlings, causing damage to the plant cell membrane system and physiological metabolic disorders. In severe cases, it can lead to wilting or even death of plants, significantly affecting the stability of crop yields and the quality of agricultural products. It has become one of the important environmental stress factors restricting the sustainable development of agricultural production. Against this backdrop, delving deeply into the response mechanisms of plants to late spring coldness not only holds significant theoretical importance but also provides a solid theoretical foundation for the breeding of new crop varieties resistant to late spring coldness. This is of profound practical and strategic significance for enhancing the stress resistance of crops, stabilizing agricultural production levels, ensuring national food security, and promoting sustainable agricultural development. This article systematically reviews the multi-level response mechanisms of plants to the stress of late spring coldness. At the physiological and biochemical level, it includes the accumulation of osmotic adjustment substances (such as soluble sugars, proline, betaine, etc.), the activation of the antioxidant enzymes system (such as superoxide dismutase, peroxidase, catalase, etc.), and the adjustment of fatty acid saturation in membrane lipid composition (mainly manifested as an increase in the proportion of unsaturated fatty acids and a relative decrease in the proportion of saturated fatty acids). At the molecular level, the focus is on the perception and transmission pathways of low-temperature signals, covering the cascade regulatory network mediated by CBF/DREB-type transcription factors and the expression dynamics of downstream cold response genes, as well as a systematic analysis of the interactive regulatory roles of calcium ion signals and plant hormones (such as abscisic acid, jasmonic acid, cytokinin, brassinolide and ethylene) in response to low temperatures. In addition, this article also reviews the application progress of cutting-edge technologies such as high-throughput sequencing and CRISPR/Cas9 gene editing in the research of plant cold tolerance mechanisms, revealing the functional characteristics of multiple key cold tolerance genes and their regulatory networks. This article aims to construct a systematic theoretical framework of the molecular mechanism of plant resistance to late spring coldness through systematic integration and in-depth review of existing research results, providing solid scientific and technological support for the breeding of new crop varieties resistant to late spring coldness, the optimization of field management strategies, and the formulation of scientific and effective disaster prevention and mitigation measures.
【Objective】The fruit branch angle is a key determinant of cotton plant architecture. Previous studies revealed differential expression of GhPDF1 in materials with extreme fruit branch angles. This study aimed to functionally characterize GhPDF1 and systematically dissect its superior allelic variations, thereby providing genetic resources and a theoretical basis for improving plant architecture and breeding machine-harvestable cotton varieties.【Method】The sequences of PDF1 homologs from 25 species, including upland cotton (Gossypium hirsutum), were obtained through homology alignment for phylogenetic analysis. A virus-induced gene silencing (VIGS) vector targeting GhPDF1 was constructed using double digestion and transformed into upland cotton to investigate its role in regulating the fruit branch angle. Single nucleotide polymorphisms (SNPs) within GhPDF1 were identified using resequencing data from 418 upland cotton accessions, with key SNPs validated by Sanger sequencing. The distribution of superior allelic variations of GhPDF1 was analyzed across Chinese cotton varieties from different breeding eras.【Result】A phylogenetic tree of the PDF1 gene from Gossypium hirsutum and its homologous genes from different species revealed that it is most closely related to Malvaceae, while being distantly related to Poaceae. Expression analysis showed that GhPDF1 was lowly expressed in large‑angle materials but highly expressed in small‑angle materials. Tissue‑specific expression profiling revealed high transcript levels in pistils, petals, and stems. VIGS‑mediated silencing of GhPDF1 significantly reduced the cell number at the fruit branch junction by approximately 170 and increased the fruit branch angle by 8.2° compared with empty‑vector controls, demonstrating its crucial role in regulating fruit branch angle. Phenotypic comparison between two allelic variants, GhPDF1GG and GhPDF1CC, indicated a significantly smaller branch angle in GhPDF1GG carriers. Moreover, the frequency of this superior allele (GhPDF1GG) increased from 92% to 98% over successive breeding periods.【Conclusion】Silencing GhPDF1 in upland cotton reduces cell proliferation at the branch junction, leading to a significant increase in the fruit branch angle. The superior allelic variant GhPDF1GG has been progressively enriched during modern cotton breeding in China.
【Objective】To study the effects of different irrigation volumes on the agronomic traits, lodging resistance and yield formation of rice, and to explore a more suitable water management plan for high-yield and stable-yield green cultivation of rice, and to provide a theoretical basis for sustainable rice production.【Method】Using WYD4 and JND667 as experimental materials, six different irrigation volume treatments were carried out: W1 (12 000 m3·hm-2), W2 (10 500 m3·hm-2), W3 (9 000 m3·hm-2), W4 (7 500 m3·hm-2), W5 (6 000 m3·hm-2) and W6 (natural rainfall). By studying the effects of different irrigation volumes on the plant architecture, resistance to lodging, photosynthetic characteristics, dry matter accumulation and yield of rice, the regulatory effects and mechanisms of different irrigation volumes on these aspects were clarified.【Result】Reducing irrigation properly increased the final tiller number, the percentage of productive tillers, leaf length of the top three leaves, and leaf area index of rice, while reducing the leaf width and leaf base angle of the top three leaves, as well as plant height. The W4 treatment can optimize the plant morphology of rice, promote plant growth, and form a good population structure. With the decrease in irrigation volume, the length of the second internode at the base of rice decreased, and the internode plumpness, breaking resistance, lodging index, and the contents of lignin and cellulose in the stem and sheath first increased and then decreased. Proper irrigation was beneficial for improving the lodging resistance of rice stems. Appropriate irrigation volume not only improves water use efficiency but also enhances the photosynthetic performance of the flag leaves of rice, the accumulation and transportation capacity of dry matter in the stem and sheath, which is beneficial to yield formation. Compared with the W1 treatment, the W4 treatment saved 37.50% of the irrigation water consumption, and the yield significantly increased by 9.07%-12.47%.【Conclusion】Under the W4 (7 500 m3·hm-2) treatment, rice has better plant morphology, lodging resistance, photosynthetic performance, and dry matter accumulation compared with other treatments. Therefore, it has the highest yield while having a high water use efficiency and can be used as a more suitable irrigation volume in this region.
