Peng Chen Yin, Wu Yu, Hua Qi Long, Shen Yong Bao
College of Forestry, Nanjing Forestry University, 159 Longpan Road, Xuanwu District, Nanjing, Jiangsu, 210037, PR China; State Key Laboratory of Rice Biology and Breeding, Zhejiang Provincial Key Laboratory of Crop Genetic Resources, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, 310058, PR China.
College of Forestry, Nanjing Forestry University, 159 Longpan Road, Xuanwu District, Nanjing, Jiangsu, 210037, PR China; Co-innovation Center for Sustainable Forestry in Southern China, Southern Tree Inspection Center National Forestry Administration, 159 Longpan Road, Xuanwu District, Nanjing, Jiangsu, 210037, PR China.
J Plant Physiol. 2025 Jan;304:154405. doi: 10.1016/j.jplph.2024.154405. Epub 2024 Dec 9.
Seed germination is a pivotal stage in the plant life cycle, with endosperm weakening and radicle elongation serving as crucial prerequisites for successful endospermic seed germination. Tilia henryana seeds exhibit deep dormancy, necessitating a period of 2-3 years to germinate in a natural environment, and the germination rate is extremely low. This study employed morphological and physiological approaches to dynamically analyzing the hydrological mechanism and the endosperm weakening process during the dormancy release of T. henryana seeds. It was found that there was no physiological post-ripening effect of embryos, but there were mechanical and physiological obstacles in endosperm. During the dormancy release process of T. henryana seeds, initial endosperm weakening occurred at the radicle-endosperm interface. In this process, the GA/ABA level is imbalanced along with a continuous decrease in IAA and SA levels. Substantial depletion of storage materials within cells resulted in degradation of endosperm cell contents, forming numerous cavities through which significant amounts of free water entered. As moisture content increased, endosperm hardness gradually decreased to approximately 5 N/0.09 cm. Furthermore, the area and content of lignin and cellulose were reduced by 58.91% and 84.49%, respectively, while the hemicellulose and pectin contents were decreased by 72.11% and 83.50%, in that order. Following treatment, the activity of pectin lyase, propectinase, galacturonase, and cellulase was observed to be 5.81, 8.72, 5.96, and 9.43 times higher, respectively, in comparison to their respective activities before treatment. The physiological changes facilitated the rapid rupture of the endosperm cell wall, leading to a transition in cell morphology from palisade-like to irregular and interlocking, thereby further expediting the weakening and cleavage of the endosperm. Additionally, T. henryana seeds exhibited high carbohydrate composition content throughout their dormancy release process, this extensive utilization of storage substances provided energy for radicle elongation and expansion.
种子萌发是植物生命周期中的一个关键阶段,胚乳弱化和胚根伸长是有胚乳种子成功萌发的关键前提条件。天目椴种子具有深度休眠特性,在自然环境中需要2至3年才能萌发,且萌发率极低。本研究采用形态学和生理学方法,动态分析了天目椴种子休眠解除过程中的水分机制和胚乳弱化过程。研究发现,胚不存在生理后熟效应,但胚乳存在机械和生理障碍。在天目椴种子休眠解除过程中,胚乳弱化最初发生在胚根 - 胚乳界面。在此过程中,GA/ABA水平失衡,同时IAA和SA水平持续下降。细胞内贮藏物质大量消耗,导致胚乳细胞内容物降解,形成许多空腔,大量自由水通过这些空腔进入。随着含水量增加,胚乳硬度逐渐降低至约5 N/0.09 cm。此外,木质素和纤维素的面积和含量分别降低了58.91%和84.49%,半纤维素和果胶含量依次降低了72.11%和83.50%。处理后,果胶裂解酶、原果胶酶、半乳糖醛酸酶和纤维素酶的活性分别比处理前高出5.81、8.72、5.96和9.43倍。这些生理变化促进了胚乳细胞壁的快速破裂,导致细胞形态从栅栏状转变为不规则且相互嵌合,从而进一步加速了胚乳的弱化和裂解。此外,天目椴种子在整个休眠解除过程中碳水化合物组成含量较高,这种贮藏物质的广泛利用为胚根伸长和扩展提供了能量。