Armstrong Jean, Armstrong William
Department of Biological Sciences, University of Hull, Kingston upon Hull HU6 7RX, UK.
Ann Bot. 2005 Sep;96(4):625-38. doi: 10.1093/aob/mci215. Epub 2005 Aug 10.
Akagare and Akiochi are diseases of rice associated with sulfide toxicity. This study investigates the possibility that rice reacts to sulfide by producing impermeable barriers in roots.
Root systems of rice, Oryza sativa cv. Norin 36, were subjected to short-term exposure to 0.174 mm sulfide (5.6 ppm) in stagnant solution. Root growth was monitored; root permeability was investigated in terms of polarographic determinations of oxygen efflux from fine laterals and the apices of adventitious roots, water uptake, anatomy and permeability to Fe2+ using potassium ferricyanide.
Both types of root responded rapidly to the sulfide with immediate cessation of growth, decreased radial oxygen loss (ROL) to the rhizospheres and reduced water uptake. Profiles of ROL measured from apex to basal regions of adventitious roots indicated that more intense barriers to ROL than normal were formed around the apices. Absorption of Fe2+ appeared to be impeded in sulfide-treated roots. In adventitious roots, deposition of lipid material (suberisation) and thickenings of walls within the superficial cell layers were obvious within a week after lifting the treatment and could prevent the emergence of laterals and commonly result in their upward longitudinal growth within the cortex. Death of laterals sometimes occurred prior to emergence; emergent laterals eventually died. In adventitious roots, blockages formed within the vascular and aeration systems in response to the sulfide.
In both adventitious and lateral roots, sulfide-induced cell wall suberization and thickening of the superficial layers were correlated with reduced permeability to O2, water and Fe2+. This study sheds light on some of the symptoms of diseases such as Akiochi. The results correlate with the authors' previous findings on the effects on roots of sulfide and lower organic acids in Phragmites and of acetic acid in rice.
赤枯病和赤苗病是与硫化物毒性相关的水稻病害。本研究调查了水稻通过在根部形成不透性屏障来应对硫化物的可能性。
将水稻品种“Norin 36”的根系在停滞溶液中短期暴露于0.174毫米硫化物（5.6 ppm）。监测根系生长；通过极谱法测定细侧根和不定根尖的氧气外流、水分吸收、解剖结构以及对亚铁离子的渗透性来研究根系通透性。
两种类型的根对硫化物反应迅速，生长立即停止，向根际的径向氧气损失（ROL）减少，水分吸收降低。从不定根的根尖到基部区域测量的ROL曲线表明，根尖周围形成了比正常情况更强的ROL屏障。在经过硫化物处理的根中，亚铁离子的吸收似乎受到阻碍。在不定根中，解除处理一周内，脂质物质的沉积（栓化）和表层细胞壁增厚明显，这可能会阻止侧根的出现，并通常导致它们在皮层内向上纵向生长。侧根有时在出现之前就死亡了；已出现的侧根最终也会死亡。在不定根中，维管系统和通气系统会因硫化物而形成堵塞。
在不定根和侧根中，硫化物诱导的细胞壁栓化和表层增厚与对氧气、水分和亚铁离子的渗透性降低相关。本研究揭示了赤苗病等病害的一些症状。这些结果与作者之前关于硫化物和低有机酸对芦苇根系以及乙酸对水稻根系影响的研究结果相关。
