宛氏拟青霉提取物增强水稻抗低温胁迫的最佳施用水平

【目的】施用生物刺激素是可持续农业中缓解作物低温胁迫的重要措施。本文主要研究了本课题组从野生沙棘内生菌提取的一种新型生物刺激素（宛氏拟青霉提取物）增强水稻抗低温胁迫的最佳施用浓度和生物学机制。【方法】通过室内培养，于野生沙棘体内分离出宛氏拟青霉 (Paecilomyces variotii) 菌株，菌株再经发酵和提纯获得供试生物刺激素PVE (Paecilomyces variotiiextracts)。以水稻为试验材料设置了萌发和液培试验，试验设0、0.05、0.10、0.20、0.50和1.00 μg/L 6个PVE施用水平，研究了低温 (15℃) 胁迫下不同浓度PVE对水稻种子萌发、幼苗生长、根系发育、光合特性和氧化损伤的影响。【结果】1)施用PVE的各处理提前打破了种子休眠，种子发芽率在第5天和第6天较CK分别提高66.7%～106.7%和28.2%～47.8%。2) PVE在0.05～0.50 μg/L浓度范围较CK显著增加地上部生物量7.9%～20.4%，提高了根系重量12.5%～28.1%。3) PVE在0.10 μg/L浓度条件下，较CK显著提高水稻总根长、根表面积、根体积和根平均直径48.0%、36.6%、36.2%和35.2%。4) PVE在0.05～0.50 μg/L浓度范围较CK显著提高水稻叶片光合速率5.1%～34.4%，并提高了叶片气孔导度和蒸腾速率。5) PVE在0.10 μg/L浓度条件下较CK显著提高叶片SOD、CAT和POD活性46.9%、9.6%和18.4%，提高根系SOD、CAT和POD活性28.0%、12.7%和16.4%，并显著降低叶片和根系中MDA含量22.0%和29.8%。6) PVE在0.05～0.50 μg/L浓度范围内均具有缓解低温胁迫的能力，以0.10 μg/L为最佳施用浓度。当超过0.10 μg/L，PVE对低温胁迫的缓解能力随着施用浓度的提升反而减弱。【结论】PVE在0.10 μg/L的浓度下可提高叶片光合能力和减少细胞氧化损伤，增加根系吸收养分的面积，显著缓解低温对水稻幼苗的胁迫。建议PVE的施用水平为0.10 μg/L。

Optimum levels of Paecilomyces variotii extracts in regulating resistance of rice seedlings to low temperature stress

【Objectives】Biostimulants are capable of alleviating abiotic stress, especially low temperature stress, and have been widely used in agriculture production. We extracted and testified a new type of biostimulant from the endophytic fungus in wild sea buckthorn. The proper dosage for the best effect was studied for rice seedlings against low temperature stress.【Methods】The tested Paecilomyces variotii extracts (PVE) was obtained through fermentation and purification of the strain Paecilomyces variotii. Germination and hydroponic pot experiments were conducted using rice as tested materials. The rice seeds were germinated and grown in nutrient solution under low temperature stress (15℃). The treated PVE dosages in the nutrient solution were 0, 0.05, 0.10, 0.20, 0.50 and 1.00 μg/L, respectively. The seed germination rate, activities of antioxidant enzymes (SOD, POD and CAT), indices of photosynthetic and growth of rice seedlings were measured.【Results】Comparing with no PVE (CK), the germination rates of rice seeds in PVE treatments were increased by 66.7%–106.7% on the 5th day, and by 28.2%–47.8% on the 6th day; the aboveground biomass increased by 7.9%–20.4% and the root weights by 12.5%–28.1% in the concentration range of 0.05–0.50 μg/L; the total root length, root surface area, root volume and average root diameter were increased by 48.0%, 36.6%, 36.2% and 35.2% under PVE concentration of 0.10 μg/L, respectively. Within the PVE concentrations of 0.05–0.50 μg/L, the photosynthetic rate of rice leaves was significantly increased from 5.1% to 34.4%, and the stomatal conductance and transpiration rate of leaves were increased as well. Under PVE concentration of 0.10 μg/L, the SOD, CAT and POD activities in leaves were increased by 46.9%, 9.6% and 18.4%, and those in roots were increased by 28.0%, 12.7% and 16.4%; the MDA contents in leaves and roots were reduced by 22.0% and 29.8%, respectively. The PVE could alleviate low temperature stress in the range of 0.05–0.50 μg/L, with the best effect in concentration of 0.10 μg/L.【Conclusions】PVE could alleviate the low temperature stress of rice seedlings by increasing nutrient uptake area of roots, leaf photosynthetic capacity and reducing cellular oxidative damage at 0.10 μg/L concentration. The appropriate dosage of PVE is 0.10 μg/L.