降雨条件下叶面喷施纳米氧化锌改善作物锌营养的效果及机制

Effects and mechanism of foliar application of zinc oxide nanoparticles on improving crop zinc nutrition under rainfall conditions

【目的】降雨条件下叶面喷施传统锌肥面临高损失率和有效性大幅降低的问题。基于纳米材料所具备的小尺寸、表面与界面效应以及强吸附效应等特性,探讨降雨条件下叶面喷施纳米锌肥的肥效及改善作物锌营养的机制,具有重要生产应用价值。【方法】试验设置5个处理:全营养液处理(CT_(1))、喷施0.1%吐温对照处理(CT_(2))、喷施ZnSO_(4)·7H_(2)O (CT_(3))、喷施EDTA-Zn (CT_(4))、喷施Nano-Zn (CT_(5))。采用室内水培试验方法,在模拟降雨条件下,比较叶面喷施纳米锌肥(ZnO-NPs)与传统锌肥(离子态锌肥ZnSO_(4)·7H_(2)O和螯合态锌肥EDTA-Zn)对花生的锌营养效果。测定3种锌肥处理对花生植株生长、生物量、净光合速率、抗氧化酶活性以及叶片中锌含量与分布的影响,探讨造成这些影响差异的生理机制。【结果】非降雨条件下,叶片喷施传统锌肥对花生生长的促进效果优于纳米锌肥,但在降雨条件下花生叶面喷施纳米态锌肥可以有效促进花生生长,花生株高较空白组CT_(2)和传统锌肥CT_(3)、CT_(4)分别显著提升16.80%、9.68%和12.85%;其地上部生物量和叶片锌含量分别达到2.48 g/株和0.078 mg/株,与对照组相比分别提高75.05%和466%,与离子态锌肥相比分别提高20.97%和19.54%,与螯合态锌肥相比分别提高24.37%和9.22%;此外,与非降雨条件下相比,降雨条件下喷施纳米锌肥的花生叶片锌含量提高77.36%,抗氧化酶活性有所上升,丙二醛含量有所下降。相反,离子态锌肥ZnSO_(4)·7H_(2)O和螯合态锌肥EDTA-Zn在降雨条件下花生地上部生物量较非降雨条件下分别降低了8.17%和23.70%,叶片锌含量分别降低了25.53%和34.28%,光合作用效率下降幅度大于纳米锌肥。利用同步辐射X射线荧光显微镜(XFM)分析表明,降雨条件下纳米态锌肥处理叶片中的信号强度显著高于其他锌肥处理。就抗淋洗能力而言,纳米锌肥的淋洗量仅为0.01 mg/株,是传统锌肥的45%~50%,而附着在叶片上的锌量为0.02 mg/株,是传统锌肥的4~5倍。这取决于肥料与叶片间的接触面积与表面张力的大小。纳米态锌肥接触角小于传统锌肥,表面张力大于传统锌肥,其粘附功(27.95 mN/m)较传统锌肥(CT_(3)和CT_(4)分别为20.33 mN/m和21.67 mN/m)分别显著增加37.48%和28.98%。【结论】在雨季及其他极端天气条件下,叶面喷施纳米锌肥可有效增强肥料与叶片之间的附着力,从而减少淋洗损失,促进花生叶片对锌的吸收,显著提高花生植株锌营养水平。

【Objectives】Rainfall leads to a high loss rate of traditional zinc fertilizers sprayed on the leaf surface,greatly reducing the effectiveness of zinc fertilizers.Based on the characteristics of nanomaterials,such as small size,surface and interface effects,and strong adsorption effects,exploring the efficacy and mechanisms of foliar application of nano zinc fertilizers under rainfall conditions has significant application value.【Methods】The experiment was setup with 5 treatments:CT_1,complete nutrient solution treatment;CT_(2),control reatment,spraying 0.1%Tween;CT_(3),spraying ZnSO_(4)·7H_(2)O;CT_(4),spraying EDTA-Zn;CT_(5),spraying Nano-Zn.Adopting the method of indoor hydroponic experiments to compare the zinc nutritional effects of foliar application of nano zinc fertilizer (ZnO-NPs) with traditional zinc fertilizers (ionic zinc fertilizer ZnSO_(4)·7H_(2O) and chelated zinc fertilizer EDTA-Zn) on peanut leaves under simulated rainfall conditions.By measuring the effects of three types of zinc fertilizer treatments on peanut plant growth,biomass,net photosynthetic rate,antioxidant enzyme activity,as well as zinc content and distribution in leaves,the physiological mechanisms causing these differences in effects were explored.【Results】Under non-rainfall conditions,foliar application of traditional zinc fertilizer was more effective for peanuts than nano zinc fertilizer.However,under rainfall conditions,foliar application of nano zinc fertilizer effectively promoted the growth of peanuts.The plant height of peanuts was significantly increased by 16.80%,9.68%,and 12.85%compared to the blank control group CT_(2) and traditional zinc fertilizers CT_(3),CT_(4),respectively.The above-ground biomass and leaf zinc content reached 2.48 g/plant and 0.078 mg/plant,respectively,which were increased by 75.05%and 466%compared to the blank group,20.97%and 19.54%compared to ionic zinc fertilizer,and 24.37%and 9.22%compared to chelated zinc fertilizer.Moreover,compared to non-rainfall conditions,leaf zinc content of peanuts under rainfall conditions was increased by 77.36%,antioxidant enzyme activity was slightly increased,and malondialdehyde content was slightly decreased.In contrast,ionic zinc fertilizer ZnSO_(4)·7H_(2O) and chelated zinc fertilizer EDTA-Zn reduced aboveground biomass by8.17%and 23.70%,and decreased leaf zinc content by 25.53%and 34.28%under rainfall conditions,with a greater decrease in photosynthetic efficiency compared to nano zinc fertilizer.Analysis using synchrotron X-ray fluorescence microscopy (XFM) showed that the signal intensity in leaves treated with nano zinc fertilizer under rainfall conditions was significantly higher than that in other zinc fertilizer treatments.In terms of rain resistance,the leaching amount of nano zinc fertilizer is only 0.01 mg/plant,which was 45%-50%of that of traditional zinc fertilizer,while the zinc content adhered to the leaves was 0.02 mg/plant,4-5 times that of traditional zinc fertilizer.This depended on the contact area and surface tension between the fertilizer and the leaves.Contact angle measurements of the three zinc fertilizers showed that the contact angle of nano zinc fertilizer was smaller than that of traditional zinc fertilizers,with a greater surface tension,and its adhesion work (27.95 mN/m) was increased by 37.48%and 28.98%compared with traditional zinc fertilizers CT_(3)’s 20.33 mN/m and CT_(4)’s 21.67mN/m,respectively.【Conclusions】Foliar application of nano zinc fertilizer can effectively enhance the adhesion between fertilizer and leaves during the rainy season and other extreme weather conditions,thereby reducing leaching losses,promoting the absorption of zinc by plant leaves,and significantly increasing the zinc nutrition levels in peanuts.