水氮耦合对黍稷幼苗形态和生理指标的影响

盆栽试验条件下,研究水氮耦合对黍稷幼苗形态和生理指标的影响。结果表明,在供水量相同条件下,黍稷幼苗株高、叶面积、根系总表面积、总体积与总根长均随施氮量的增加而增加,供水量相同时根冠比随施氮量增加而降低;施氮量相同条件下随灌水量的增加黍稷幼苗各指标呈相似变化趋势,各处理与对照差异均达到了显著水平。不同的水氮处理组合,黍稷叶片叶绿素含量差异显著,以高水高氮的W3N3处理[土壤田间持水量70%~80%,尿素用量4.6 g.kg 1(土)]为最大值,低水低氮的W1N1处理[土壤田间持水量30%~40%,尿素用量为0 g.kg 1(土)]为最小值;灌水量相同,叶绿素含量随施氮量增加而增加;施氮量相同,叶绿素含量也随灌水量增加而增加,水分和氮素对叶片叶绿素含量的影响表现为明显的协同效应;黍稷幼苗叶片电解质外渗率的变化趋势则相反。黍稷根系超氧化物歧化酶活性以低水中氮的W1N2处理[土壤田间持水量30%~40%,尿素用量2.3 g.kg 1(土)]为最高,达213.71 U.g 1(FW);W3N3最低,为72.93 U.g 1(FW)。水分相同条件下黍稷幼苗根系过氧化物酶活性、丙二醛含量、可溶性糖含量均随施氮量的增加而降低,施氮量相同时则随灌水量的增加而降低。根系活力则相反,且各处理间差异均达到显著水平。在干旱胁迫条件下,适当的增施氮肥可以提高苗期黍稷的叶绿素含量和根系活力,增加根系总表面积、总体积与总根长,降低根系丙二醛含量,在一定程度上缓解干旱胁迫的影响。

Effect of irrigation and nitrogen supply on physio-morphologicalindices of broomcorn millet at seedling stage

The effects of irrigation and nitrogen application on physio-morphological indices of broomcorn millet at seedling stage was studied in a pot experiment. The results indicated that plant height, leaf area, total root surface area, root volume and root length increased with increasing nitrogen supply at equivalent moisture. However, root to shoot ratio decreased with increasing nitrogen supply. All indices were similar in trends to the water and nitrogen supply, with each treatment significantly different from the control. Chlorophyll content of broomcorn millet at seedling stage remarkably changed under different water and nitrogen conditions. High water and nitrogen treatments [at soil moisture of 70%~80% field capacity and urea nitrogen at 4.6 g·kg^-1(soil), W3N3] had the maximum chlorophyll content while low water and nitrogen treatments [at soil moisture of 30%~40% field capacity and 0 g(urea)·kg^-1(soil), W1N1] had the minimum content. At constant moisture, chlorophyll content increased with increasing nitrogen supply. Also at constant nitrogen supply, chlorophyll content increased with increasing water supply. Hence water and nitrogen had an apparent synergetic effect on leaf chlorophyll content of broomcorn millet at seedling stage. Electrolyte leakage rate showed the reverse tendency. Root SOD activity of broomcorn millet at seedling stage was maximum [213.71 U·g^-1(FW)] under W1N2 [soil moisture of 30%~40% field capacity and 2.3 g(urea)·kg^-1(soil)] and minimum [72.93 U·g^-1(FW)] under W3N3. POD activity, MDA content and soluble sugar content decreased with increasing nitrogen at constant soil moisture and decreased with increasing water at constant soil nitrogen. The reverse was noted for root activity with each treatment significantly different. Under drought stress conditions, increase in nitrogen fertilizer proportionately improved chlorophyll content and root activity of broomcorn millet at seedling stage. It also increased total root surface area, root volume and root length. Increase in nitrogen fertilizer, however, reduced root MDA content. To a certain extent, increased nitrogen fertilizer responsively relieved the impact of drought stress.