棉花幼苗钾吸收的系统反馈调节初步研究

Systemic Feedback Regulation of K^+ Uptake in Cotton at Seedling Stage

以中棉所41和辽棉17为材料,采用单接穗双砧木嫁接的方法构建分根体系,在营养液培养条件下研究棉花幼苗钾吸收的系统反馈调节。分根处理6 d后,高钾侧(2.50 mmol L–1)根系(Sp.+K)的吸收能力受到低钾侧(0.01 mmol L–1)K+需求信号的诱导,吸收动力学参数Imax(最大吸收速率)与整根高钾对照(C.+K)相比增加了79%~92%;低钾侧根系(Sp.-K)的Imax则受到高钾侧K+供应信号的抑制,与整根低钾对照(C.K)相比下降了27%~40%。中棉所41分根处理3 d后去除低钾侧根系,保留的高钾侧根系失去K+需求信号的诱导,其Imax下降。棉花幼苗K+吸收的这种反馈调节与地上部和根系的K+含量关系不大。

This hydroponic split-root experiment was conducted to elucidate the long-distance systemic regulation of K＋uptake in cotton（Gossypium hirsutum L.）seedlings with two cotton cultivars CCRI41 and Liaomian17 as materials.Inverted Y grafting（one scion/two rootstocks,hypocotyl-to-hypocotyl）was used to establish split-root plants.The K＋-uptake characteristics of cotton seedlings were measured by depletion method and described by kinetic parameters,Imax（the maximum rate of uptake）,Km（the external concentration at which the uptake rate is 0.5 Imax）and Cmin（the external concentration at which no net flux occurs）.In relative to the sufficient K＋control（both root halves supplied with 2.50 mmol L–1K＋）,the root half supplied with 2.50 mmol L–1 K＋for six days showed 79% to 92% more Imax owing to the induction of K＋-demand signal derived from the root half starved with K＋.Compared with the K＋starvation control（both root halves supplied with 0.01 mmol L–1K＋）,Imax of root half supplied with 0.01 mmol L–1K＋for six days decreased by 27% to 40% due to the suppression of K＋-supply signal initiated by the root half grown in sufficient K＋.When the root half starved with K＋in CCRI41 was removed after three days of split-root treatment,the remained root half incessantly supplied with 2.50 mmol L–1K＋for six days had less Imax relative to the whole split-root plants,which is likely attributed to the loss of K＋-demand signal from the other root half during last three days.This systemic feedback regulation of K＋uptake in cotton seedlings was independent of K＋content of either root or shoot.