局部供应硝酸盐诱导玉米侧根生长的基因型差异

以两个玉米(Zea.mays.L.)自交系478和Wu312为研究材料,采用琼脂培养方法,研究局部供应不同浓度的硝酸盐(NO3-)对侧根生长的影响。结果表明,根系局部供应0.5mmol/L硝酸盐,可以促进两个基因型相应部位的侧根长度,对478的促进效果显著高于Wu312。在双层局部供应0.5mmol/L硝酸盐时,能够刺激两个层次478局部侧根伸长,而Wu312只在上层表现出促进作用。多浓度试验结果表明,在0.5～25mmol/L范围内,局部供应硝酸盐均能在478上表现促进效果。而在Wu312上,当局部硝酸盐浓度超过5mmol/L,刺激作用消失。在低浓度范围内,局部供氮不影响侧根。当局部供应的硝酸盐浓度超过5mmol/L时,Wu312的侧根数量急剧下降,超过15mmol/L后,478的侧根数量开始下降。478侧根对局部硝酸盐刺激的响应能力显著高于Wu312。

Genotypic difference of maize lateral roots in response to local nitrate supply

Lateral roots are primary organs for plant to take up and utilize soil nutrients. Their development is controlled by the internal genetic factors and mineral nutrient levels in the growth environment. In this paper, two maize (Zea mays L.) inbred lines, 478 and Wu312, were used to study the effect of local supplied nitrate (NO~-_3) with different concentrations on lateral roots' growth with an agar culture system. The results showed that a localized supply of 0.5 (mmol/L) nitrate could stimulate lateral roots' length of corresponding place for both maize inbred lines, with a stronger effect on 478 than Wu312. The elongation of lateral roots of 478 had an increase by 41.3% in comparison of control group, whereas in Wu312, it only has an increase by 21.7%. When 0.5 (mmol/L) nitrate was supplied in two segments locally along the radical, elongation of lateral roots in both segments had a increase in 478, whereas in Wu312, only lateral roots in the upper segment increased. External nitrate concentration being 1 (mmol/L) was optimum for the lateral roots growth. When external nitrate concentrations were lower than 1 (mmol/L), they could stimulate lateral roots growth. However, when external nitrate concentrations were higher than 1 (mmol/L), the effect of stimulation reduced. Local supplied nitrate that ranged from 0.5 to 25(mmol/L) displayed a promotion action on 478. Under these conditions the stimulation effect of local nitrate was higher than uniform nitrate. In Wu312, however, the stimulation effect was only displayed as long as (local) nitrate supply was lower than 5(mmol/L). At low nitrate concentration, localized supply of nitrate had no significant influence on the number of lateral roots. When localized nitrate supply was higher than 5(mmol/L), lateral root number of Wu312 decreased sharply. For 478, lateral root number decreased when local nitrate was higher than 15(mmol/L). Comparing the response to local nitrate stimulation, the lateral root of 478 was more responsive than that of Wu312. However, the mechanism involved needs to be further investigated.