作 者 ：李永旗,董合林,李鹏程,刘敬然,刘爱忠,王晓茹,杜军,李亚兵
期 刊 ：植物营养与肥料学报 2014年 20卷 6期 页码：1553-1559
Keywords:foliagespray, 15N-urea, absorption, utilization, physiologicalandbiochemicalcharacteristics,
摘 要 ：【目的】苗期棉花根系发育缓慢,吸收能力弱,根系吸收的氮素不能满足棉株生长发育的需要,很容易出现僵苗、 弱苗。叶面施氮可以及时补充氮素营养,解决棉花苗期阶段性营养不足的问题。本研究利用15N同位素示踪技术研究喷施尿素对棉花苗期氮素吸收利用及生理生化特性的影响,以明确棉花苗期叶面喷施尿素的适宜浓度,了解其促进棉花生长发育的机理。【方法】本试验选用黄河流域常规栽培品种中棉所79为试验材料,采用随机区组设计,在棉花苗期叶面喷施0.5%、 1%和2%的15N-尿素溶液,以喷清水为对照,调查了尿素不同喷施浓度棉花氮素的吸收利用及生理生化特性。【结果】1)叶面喷施15N-尿素能显著提高棉株15N含量,各施氮处理棉株内15N含量随时间的变化趋势一致,即叶面喷施后2～96 h之间,逐渐升高,96 h达到最高,此后出现下降。2)棉株可以快速吸收叶面喷施的15N-尿素,各处理棉株叶面氮素平均吸收速率的变化趋势一致,因中午气孔关闭,2～4 h出现降低;4～6 h达到最大,期间急剧上升;6～8 h急剧下降,8～12 h下降也较快,12 h后缓慢下降。0～12 h平均吸收速率非常高,为0.23～0.29 mg/(g·h)。棉株对于叶施氮素的吸收主要出现在喷施后12 h之内。3)15N-尿素浓度为0.5%、 1%时,叶面吸收显著促进了根系氮素吸收,且根系吸收的氮很快被转运到地上部分。4)1%尿素喷施浓度内,硝酸还原酶、 谷氨酰胺合成酶活性,叶绿素含量的变化趋势一致,均随尿素喷施浓度的增加而提高,在喷施浓度为1%时达到峰值,超过1%后开始下降。【结论】叶面尿素喷施浓度在0.5%～2%之间均能显著提高棉株15N含量,促进棉株的氮素代谢,以1%效果最佳。棉株对于喷施氮素的吸收主要发生在喷施后0～12 h,平均吸收速率为0.23～0.29 mg/(g·h),96 h棉株中15N含量达到最高。棉花叶面施氮促进了根系对氮素的吸收。叶面施氮主要通过增强硝酸还原酶、 谷氨酰胺合成酶活性,提高叶绿素含量,增加叶面积,促进叶片的光合作用,以此提高氮素利用效率,增加棉花株高和总生物量。
Abstract:【Objectives】Cotton roots grow slow at the seedling stage, so the absorption of nitrogen by roots can not meet the needs of growth and development of cotton plants, deadlock or weak seedlings are often happened as a result. Foliar nitrogen application can replenish nitrogen nutrition in time and solve problem of periodic innutrition at the seedling stage. In order to clarify the optimum urea concentration of foliar spraying and understand its mechanism of promoting cotton growth and development, the 15N isotope tracer technique was used to investigate effects of foliage spraying urea on nitrogen uptake and utilization, and physiological and biochemical characteristics of cotton.【Methods】A field experiment with randomized complete-block design were conducted with cotton cultivar CCRI79 as an experimental material. Four foliage spraying concentration of 15N-urea solution: 0%, 0.5%, 1% and 2% were sprayed at the seedling stage of cotton seedlings. The uptake and utilization, and the physiological and biochemical characteristics of cotton were investigated. 【Results】1) The foliage spraying of 15N-urea can significantly improve the 15N content of cotton plants. The 15N uptake by cotton leaves is increased gradually from 2 to 96 h after spraying, then declined. 2) The sprayed 15N-urea can be absorbed quickly by cotton plants, and the average N absorption rates with time are consistent in all the treatments. The main uptake of the sprayed N is occured within 12 h.. The absorption rates sharply rise to the highest from 4-6 h after spraying, then decline sharply from 6-8 h, keep fast from 8-12 h and slowdown after 12 h. The average nitrogen absorption rates from 0-12 h is 0.23-0.29 mg/(g·h). 3) The foliar supplement of N nutrition can significantly promote the uptake and up transport of the nitrogen absorbed by roots under the treatments of 0.5% and 1% urea concentrations. 4) Under the urea spraying concentrations from 0% to 1%, the nitrate reductase activity, glutamine synthetase activity and chlorophyll content are increased with the increase of spraying concentrations. The physiological and biochemical indexes are the highest under the treatment of 1% concentration. 【Conclusions】The foliar spraying of urea can improve the N nutrition of cotton seedlings significantly by both the direct absorption of foliar sprayed N and accelerated N uptake and up transport by root. The uptakes of sprayed 15N by cotton plants are mainly occurred within the 12 hours after spraying, with the average absorption rates of 0.231-0.293 mg/(g·h), depending on the spraying concentrations. The contents of 15N in cotton plants keep increasing until the 96 hours after spraying. The foliar supplement of N nutrition promote photosynthesis by increasing the activities of nitrate reductase and glutamine synthetase, increasing the chlorophyll content, and improve leaf area of cotton plants. The suitable spray concentration is 1% of urea at the seedling stage of cotton.
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