電信號和細胞分裂素調節玉米和大麥根對離子的吸收
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Conflux + I&E Flux + I&M Flux = 細胞內外離子/分子同時檢測完整方案 |
根部的離子吸收是維持植物細胞營養平衡最重要的一步，成熟區的營養吸收受莖和根尖的系統控制。這個過程受到電信號、壓力、機械刺激、光照和細胞分裂素的調節。 2009年，科學家通過非損傷微測技術研究了玉米和大麥根部的離子流，發現短期的光照使H+外流減小，K+從吸收轉變為外流。切斷的玉米和大麥的根在低鹽環境下H+外流減小，K+內流停止。加入100mM NaCl，壓力劇烈變化，但是離子流不受影響。切除了大麥根尖部分，離子流從小內流轉變為大的內流。激動素（2-4 μM，一種細胞分裂素）引起了K+更大的內流，說明離子的運輸被根尖合成的細胞分裂素所調控。 本研究說明快速的電信號和細胞分裂素能夠調節根的營養吸收，下一步的研究將集中在通過增加光強而引發的電信號如何調節植物離子運輸和營養吸收。這項工作為我們如何調節植物的營養吸收提供了依據。
關鍵詞：激動素(kinetin); 長距離信號(long-distance signalling); K+ ; H+
參考文獻：Shabala S,et al. Plant, Cell and Environment (2009) 32, 194–207
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Abstract： Nutrient acquisition in the mature root zone is under systemic control by the shoot and the root tip. In maize, exposure of the shoot to light induces short-term (within1–2 min) effects on net K+ and H+ transport at the root surface. H+ efflux decreased (from -18 to -12 nmol m-2 s-1) and K+ uptake (~2 nmol m-2 s-1) reverted to efflux (~-3 nmol m-2 s-1). Xylem probing revealed that the transroot (electrical) potential drop between xylem vessels and an external electrode responded within seconds to a stepwise increase in light intensity; xylem pressure started to decrease after a ~3 min delay, favouring electrical as opposed to hydraulic signalling. Cutting of maize and barley roots at the base reduced H+ efflux and stopped K+ influx in low-salt medium; xylem pressure rapidly increased to atmospheric levels.With 100 mM NaCl added to the bath, the pressure jump upon cutting was more dramatic, but fluxes remained unaffected, providing further evidence against hydraulic regulation of ion uptake. Following excision of the apical part of barley roots, influx changed to large efflux (-50 nmol m-2 s-1). Kinetin (2–4 μM), a synthetic cytokinin, reversed this effect. Regulation of ion transport by root-tip-synthesized cytokinins is discussed. |
