硝酸盐供应对玉米侧根生长的影响

Effect of NO_3^- Supply on Lateral Root Growth in Maize Plants

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,研究不同浓度NO3- 对侧根生长的影响。结果表明,在外部浓度0.01-1.0 mmol／L范围内,NO3-供应能显著增加侧根的长度及根 生物量。但当NO3-供应超过1.0 mmol/L后,侧根长度 开始下降。当NO3-供应分别在超过5.0(Wu312)与10 (478)mmol／L后,侧根密度显著下降。在10 mmol／L NO3-下,Wu312的侧根生长几乎完全被抑制。而478在 20 mmol／L时,侧根密度仍可达到其最大值的30％(主 根)-50％(胚根)。植株地上部全氮及硝酸盐含量随 NO3-供应的增加而升高,二者与侧根长度、侧根密度 及冠根比的数学函数关系相同。

Growth of lateral roots is regulated by both environmental factors and nitrate (NO3-) content of the plant. The mechanism involved is not clearly understood. Two maize (Zea mays L.) inbred lines (478 and Wu312) were used to study the effect of different nitrate supply on lateral root (LR) growth by a whole plants agar culture. The results showed that increasing NO3-concentration in nutrient solution from 0.01 to 1.0 mmol/L significantly increased the LR length and root biomass (Fig.1, Fig.4). Lateral root density changed little with NO3- increase up to 5×10-3 mol/L (for Wu312) -10×10-3 mol/L (for 478), then decreased significantly with increasing NO3-(Fig.3). The inhibitory effect of high NO3- on root growth was weaker in 478 than in Wu312. The growth of lateral roots in Wu312 was completely inhibited by NO3- at a concentration of 10× 10-3 mol/L, whereas LR density of 478 could reach 30% (axial) and 50% (radicle) of its maximum even at NO3- 20×10-3 mol/L (Fig. 3). Both the shoot total N and shoot nitrate con- tent increased with increasing NO3- level (Fig.5, Fig.6). They had similar mathematic functions with shoot/root ratio (Exponential Decay), LR density (Gaussian) and LR length (Parabola). When shoot N content exceed about 1.6 mol/kg and NO3- content exceed 0.22 mol/kg, shoot/root ratio increased rapidly (Fig.7); when the shoot N content exceed about 1.5 and NO3- exceed 0.16 mol/kg, LR densities began to decrease (Fig. 8); when shoot N content reached about 1 mol/kg and NO3- content reached 0.10 mol/kg, the LR lengths began to decrease (Fig.9). The possible relationship between shoot NO3- content and lateral root growth was discussed.