Abstract:

Frequent extreme climate events such as droughts and high temperatures caused by global warming have led to a 32%-53% decrease in the emergence rate of direct-seeded rice compared with the baseline level, seriously threatening food security. Hydropriming, as a low-cost seed pretreatment technology without chemical residues, can enhance germination efficiency and stress resistance by regulating seed metabolism and gene expression. In this study, four different rice varieties, namely Wuyoudao 4, Yuxiangyou 8133, Yongyou 4949, and Yuxiangnuo 1, were used as materials. Combined with the determination of seed coat thickness, the seed germination process and physiological responses under hydropriming (T treatment, hydropriming treatment) and non-priming (CK, control treatment) were analyzed to explore the effect of seed coat thickness on priming efficacy. The results showed that there were differences in seed coat thickness among the four varieties, which were closely correlated with germination and resistance indices after priming. The T treatment significantly advanced the initiation time of germination by 1-2 days, and the germination index was significantly increased. For example, the germination indices of Wuyoudao 4 and Yongyou 4949 increased by 42.87% and 24.03%, respectively. However, the germination energy and mean germination time decreased, and there was no significant difference in the final germination rate between the T treatment and CK. In terms of resistance, the T treatment reduced the malondialdehyde (MDA) content and increased the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) of all varieties. For instance, the POD activity of Wuyoudao 4 in the T treatment was 65.52% significant higher than that in CK. Yuxiangnuo 1, with a thicker seed coat, showed an 22.39% increase in root length under the T treatment compared to CK. Its biomass and root-shoot ratio, and SOD activity increased singnificantly, with its biomass and root-shoot ratio being the highest among the four cultivars. In contrast, Yongyou 4949, with a thinner seed coat, exhibited the lowest germination energy and the largest decrease in MDA content(43.62%). The study indicated that seed coat thickness affects the germination response and resistance performance of rice seeds to hydropriming by regulating water absorption and the antioxidant system, providing a theoretical basis for drought-tolerant variety screening and optimization of direct-seeding techniques.

Key words: rice, seed coat thickness, germination rate, priming, antioxidant characteristics

摘要：

全球气候变暖导致干旱、高温等极端气候事件频繁发生，这使得直播稻的出苗率相较于基线水平下降32%~53%，对粮食安全构成了严重威胁。清水引发作为一种低成本且无化学残留的种子预处理技术，能够通过调控种子的代谢过程与基因表达，提高种子的萌发率以及抗逆能力。本研究选取了五优稻4号、渝香优8133、甬优4949、渝香糯1号4个不同类型的水稻品种作为试验材料，结合种皮厚度测定，对比分析清水引发（T处理）与未引发（CK）条件下种子的萌发进程和生理响应情况，同时探究种皮厚度对引发效果的影响。结果显示，这4个水稻品种的种皮厚度存在差异，并且与引发后的萌发及抗性指标密切相关。经过T处理后，种子的萌发起始时间较CK显著提前1~2 d，发芽指数亦显著提高，五优稻4号、甬优4949的发芽指数分别提升42.87%和24.03%；不过，发芽势和平均发芽时间有所降低，最终发芽率与 CK无显著差异。在抗性方面，T处理使所有参试品种的丙二醛（MDA）含量降低，超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）活性提升，五优稻4号T处理下的POD活性比CK显著高65.52%。种皮较厚的渝香糯1号在T处理下根长较CK增加22.39%，生物量、根冠比和SOD活性提升显著，且生物量和根冠比在4个品种中最高；而种皮较薄的甬优4949则表现出发芽势最低、MDA 降幅（43.62%）最大的特点。研究表明，种皮厚度通过调控水分吸收和抗氧化系统，影响水稻种子对清水引发的萌发响应以及抗性表现，这一发现为耐旱品种的筛选和直播技术的优化提供了理论依据。

关键词: 水稻, 种皮厚度, 发芽率, 引发, 抗氧化特性