Table 1_Regulation effect of seed priming on sowing rate of direct seeding of rice under salt stress.pdf

Direct seeding of rice (DSR) is a widely used method for its labor- and cost-saving advantages. However, the global intensification of soil salinization presents a significant challenge to food security. Increasing sowing rates is a common practice to enhance germination under salt stress, although it leads to higher seed costs. Recently, seed priming has emerged as an effective technique to improve seedling emergence under abiotic stress, but the regulation of seed priming treatment on the sowing rate of DSR under saline soil conditions has rarely been reported. Therefore, field experiments were conducted at two salinity levels of 1.5‰ (1.5 g kg−1) (T2) and 3.0‰ (3 g kg−1) (T3) and under one non-saline condition (0‰) (T1). The control (P1) consisted of non-primed seeds, while priming treatments included 160 mg L−¹ ascorbic acid (P2), γ-aminobutyric acid (P3), and 200 mg L−¹ zinc oxide nanoparticles (P4); three sowing rates were applied: 90 (S1), 150 (S2), and 240 seeds m−2 (S3). Our results demonstrated that under T1–T3, the germination rate, α-amylase activity, and soluble sugar and protein contents were significantly increased after priming treatments. The contents of reactive oxygen species (i.e., O2− and H2O2) and malondialdehyde (MDA) were decreased, while the activities of enzymatic antioxidants (i.e., superoxide dismutase, peroxidase, and catalase) and the K+/Na+ ratio of rice were significantly increased after the above seed priming treatments. Under T1–T3, the grain yield increased by 13.39%–36.94% after priming treatments, primarily due to enhanced seed germination, which boosted panicle number per unit area. Among P2–P4 treatments, P4 treatment consistently resulted in the highest yield increase (26.96%–36.94%) compared to P1, outperforming P2 and P3 under T1–T3. Furthermore, under T1–T3, the grain yield with priming treatment at 90 seeds m−2 was equivalent to that obtained without priming treatment at 240 seeds m−2. The potential mechanisms by which priming treatments enhance rice salt tolerance include increased levels of osmoregulatory substances and elevated activities of antioxidant enzymes, which collectively support improved seed germination. Therefore, to optimize the economic benefits of DSR when the salt concentration is below 3‰, the sowing rate could be reduced to 90 seeds m−2 using ZnO-nanoparticle priming treatment.

水稻直播（Direct Seeding of Rice, DSR）因具备省工、节本的优势而被广泛应用。然而，全球范围内土壤盐渍化的加剧对粮食安全构成了严峻挑战。生产中常通过提高播种量来提升盐胁迫下的种子萌发率，但这会增加种子成本。近年来，种子引发（seed priming）作为一项可改善非生物胁迫下幼苗出苗的有效技术逐渐受到关注，但针对盐渍土条件下种子引发处理对水稻直播播种量调控效应的研究鲜有报道。为此，本研究设置了0‰（T1，非盐胁迫）、1.5‰（T2，1.5 g·kg⁻¹）和3.0‰（T3，3 g·kg⁻¹）三个盐度水平的田间试验。试验设置对照组（P1，未引发种子），以及三种引发处理组：160 mg·L⁻¹抗坏血酸（ascorbic acid, P2）、160 mg·L⁻¹γ-氨基丁酸（γ-aminobutyric acid, P3）和200 mg·L⁻¹氧化锌纳米颗粒（zinc oxide nanoparticles, P4）；同时设置3个播种量梯度：90粒·m⁻²（S1）、150粒·m⁻²（S2）和240粒·m⁻²（S3）。研究结果表明，在T1至T3盐度条件下，经种子引发处理后，水稻的萌发率、α-淀粉酶活性以及可溶性糖和可溶性蛋白含量均显著提升；活性氧（reactive oxygen species, 即O₂⁻和H₂O₂）含量与丙二醛（malondialdehyde, MDA）含量显著降低，而抗氧化酶（超氧化物歧化酶、过氧化物酶和过氧化氢酶）活性以及水稻K⁺/Na⁺比值均显著升高。在T1至T3条件下，引发处理后水稻籽粒产量较对照提升13.39%~36.94%，这主要得益于种子萌发性能改善，进而提升了单位面积穗数。在P2至P4三个引发处理中，P4处理的增产效果始终最优，较P1增产26.96%~36.94%，在T1至T3条件下均优于P2和P3。此外，在T1至T3条件下，采用90粒·m⁻²播种量结合种子引发处理的籽粒产量，与未引发处理下240粒·m⁻²播种量的产量相当。种子引发提升水稻耐盐性的潜在机制包括：渗透调节物质含量升高与抗氧化酶活性增强，共同促进了种子萌发性能。因此，当土壤盐浓度低于3‰时，为优化水稻直播的经济效益，可采用氧化锌纳米颗粒引发处理，并将播种量降至90粒·m⁻²。