慈姑(Sagittaria trifolia)根系泌氧特征

借助高精度溶解氧微电极,研究了自然沉积物中慈姑(Sagittaria trifolia)根不同部位的泌氧能力差异以及光照对根系泌氧能力的影响。结果表明,慈姑根系不同部位的泌氧能力存在差异,光照和黑暗条件下根区氧气扩散层厚度由大到小依次为1/2根长(0.98、0.72 mm)、3/4根长(0.68、0.28 mm)、根尖(0.58、0.44 mm)和1/4根长(0.42、0.32 mm);光照条件下不同根长部位根表面溶解氧含量由大到小依次为1/2根长〔64.56%(以%空气饱和度计)〕、3/4根长(52.73%)、根尖(38.55%)和1/4根长(20.55%),这与根部泌氧屏障、通气组织发育程度和根组织呼吸代谢有关。无论有无光照,慈姑根均有泌氧产生,光照条件下根表面溶解氧含量和根区氧气扩散层厚度均高于黑暗条件;在光照和黑暗条件下1/2根长处根表面溶解氧含量均显著高于其他测定点(P<0.05);除1/2根长处以外的其他测定点,在光照条件下的根表面溶解氧含量差异显著(P<0.05),但在黑暗条件下趋于相同(P>0.05)。

Oxygen Excretion by Roots of Sagittaria trifolia

Root excretion of oxygen is an important feature of Sagittaria trifolia.For better understanding the characteristics of the radial oxygen loss(ROL) from roots of the plant in natural sediment,high-precision dissolved oxygen microelectrodes were used to measure penetration depth and distribution of oxygen under different light intensities(dark and light).Substantial difference in oxygen distribution was observed between parts of the roots.Thickness of the oxygen diffusion layer in the rhizosphere under light and in dark varied along the root in the following order:at 1/2 of the root length(0.98 and 0.72 mm)>at 3/4(0.68 and 0.28 mm)>at root tip(0.58 and 0.44 mm)>at 1/4 of the root(0.42 and 0.32 mm).Content of dissolved oxygen on root surface under light varied along the root in the following order:at 1/2 of the root length(64.56% of air saturation)>at 3/4(52.73%)>at root tip(38.55%)>at 1/4(20.55%),which was related to barrier to ROL,development of aerenchyma,and metabolism and respiration of the tissue.ROL from the roots of S.trifolia,no matter under light or in dark,occurs all the time,and is significantly affected by light intensity.Both the content of dissolved oxygen on root surface and the thickness of the oxygen diffusion layer in the rhizosphere are higher under light than in dark.Among all the measuring points,the point at 1/2 of the root length had the highest ROL in both light conditions(P<0.05).Under light significant differences were found between all the other points in content of dissolved oxygen,but in dark the contents of dissolved oxygen at these points tended to be on the same level(P>0.05).