光照和生长阶段对菖蒲根系泌氧的影响

以自然湖泊沉积物为研究基质,利用微型电机控制溶氧微电极实现纵向精确微位移,在照光与遮光条件下,对典型湿地植物菖蒲幼苗、成株根系根基部起总根长1/4处(根1/4)、根系中部(根1/2)、从根基部起总根长3/4处(根3/4)及根尖(根1)处根系微界面径向溶氧浓度变化进行原位精确测定。结果表明:无论有无光照,菖蒲幼苗、成株根系不同部位均存在从根表面至沉积物氧饱和度由高到低的氧扩散层,其厚度0.18—0.68 mm;根1/2、3/4、1处氧扩散能力菖蒲成株较幼苗显著增强(P<0.01),根1/4处二者则无显著差异(P>0.05);光照对菖蒲幼苗、成株根系不同部位氧扩散能力的影响存在差异,光照对菖蒲幼苗根1/2及菖蒲成株根1/2、根3/4处影响显著(照光组显著高于遮光组,P<0.01),而对菖蒲幼苗根1/4、根3/4、根1及菖蒲成株根1/4、根1处无显著影响(P>0.05);从根系泌氧空间差异上看,照光条件下菖蒲幼苗、成株分别表现为根1/2>根3/4≈根1≈根1/4(P<0.01,P>0.05)和根1/2>根3/4>根1>根1/4(P<0.01),遮光条件下菖蒲幼苗、成株分别表现为根1/2≈根3/4≈根1≈根1/4(P>0.05)和根1/2>根3/4≈根1>根1/4(P<0.01,P>0.05)。

The influence of light and growth stage on oxygen diffusion capacity of Acorus calamus roots

Under light or dark conditions, the change of the radial oxygen loss at the points of 1/4, 1/2 and 3/4 far from root stem base (root 1/4, 1/2, 3/4) and root tip (root 1) and its micro-interface were measured in-situ by soluble oxygen microelectrode for A. calamus seedlings and adult A. calamus plants in a typical wetland.Sediment from natural lakes was used as experimental substrates and a micro motor was used to control the soluble oxygen microelectrode to verify the accuracy of the vertical micro position. The result showed that: there was always an oxygen diffusion layer with an increasing gradient of oxygen saturation from the root surface to the anaerobic layer of sediment in the A.calamus roots in light or dark conditions. Oxygen diffusion layer thickness was 0.18-0.68 mm and maximum oxygen saturation was 42.9% under light condition and oxygen diffusion layer thickness was 0.22-0.38mm and maximum oxygen saturation was 21.5% under dark condition.The oxygen diffusion capacity of root points at 1/2, 3/4, 1 of adult plants was significantly higher than those of the seedlings but was insignificant at the point of 1/4, oxygen diffusion layer thickness increased from 0.40, 0.32, 0.26mm to 0.68, 0.52, 0.46mm and maximum oxygen saturation increased from 6.4%, 3.6%, 4.1% to 42.9%, 22.5%, 10.2% under light condition. Oxygen diffusion layer thickness increased from 0.30, 0.28, 0.24mm to 0.38, 0.34, 0.36mm and maximum oxygen saturation increased from 3.5%, 4.0%, 3.1% to 21.5%, 12.5%, 11.6% under dark condition.The influence of light on oxygen diffusion capacity of different root part at different plant growth stages were different. Light had significant influence on root 1/2 of seedlings and root 1/2, 3/4 of adult plant (light treatment exceeded dark treatment significantly, P<0.01), but had no significant influence on root 1/4, 3/4, 1 of seedlings and root 1/4, 1 of adult plant (P >0.05). As to the spatial variation of root oxygen release, it showed a tendency of root 1/2> root 3/4, root 1, root 1/4(P<0.01,P >0.05)and root 1/2> root 3/4> root 1> root 1/4(P<0.01)respectively for seedlings and adult plants under light condition. It showed a tendency of no significant difference among root 1/2, 3/4, 1, 1/4 and root 1/2> root 3/4, 1> root 1/4(P<0.01)respectively for seedlings and adult plants under dark condition.The phenomenon of minimum oxygen diffusion capacity at root 1/4 was mainly induced by the oxygen diffusion barrier in root stem base. Spatial difference of the oxygen diffusion capacity of root 1/2, 3/4, 1 were mainly affected by internal oxygen diffusion capacity and root biomass differences. The stronger the internal oxygen diffusion capacity, the more significant influence on spatial difference of the root oxygen diffusion capacity induced by root biomass differences. On the contrary, root biomass difference would not lead to spatial difference of the root oxygen diffusion capacity. For example, the oxygen diffusion capacity of the seedlings had no significant difference among root 1/2, 3/4, 1 under dark condition.