缺钾诱导早衰条件下,根-冠互作对棉花叶片早衰的调节包括地上部主导型和根系主导型.本研究主要观察缺钾条件下2种根-冠互作类型单接穗单砧木(I型)和双接穗单砧木(Y型)嫁接接穗下胚轴的解剖结构,并判断其与下胚轴木质部中CTK和ABA的流量是否有关.结果表明,地上部主导型I型嫁接接穗下胚轴解剖结构与砧木品种更为相似,与其木质部CTK和ABA的流量主要受地上部调节不符;Y型嫁接2个不同品种接穗之间下胚轴解剖结构的差异与其木质部CTK和ABA流量的差异虽然具有相关性,但可能是一种伴生现象.根系主导型I型嫁接砧木对接穗的影响很大,但这与砧木对接穗下胚轴木质部CTK和ABA流量的调节可能也是一种伴生现象;Y型嫁接2个不同接穗之间下胚轴解剖结构差异较大,与二者之间CTK和ABA流量无显著差异的结果不符.因此,棉花叶片早衰2种根-冠互作类型接穗下胚轴解剖结构与其木质部中CTK和ABA的流量无关.此外,无论是地上部主导型还是根系主导型,2个品种自身嫁接的接穗下胚轴结构差异在Y型嫁接与I型嫁接中不一致,可能与Y型嫁接的2个接穗之间存在冠-冠互作有关.%Under potassium (K) deficiency, effect of root-shoot interaction on cotton leaf premature senescence includes shoot-dominated and root-dominated patterns. Indirect evidences from grafting study under K deficiency have suggested that scion hypocotyl of shoot-dominated pattern (CCRI41 and SCRC22 combination) may have the ability to synthesize, metabolize and/or radially transport cytokinin (CTK) and abscisic acid (ABA), while that of root-dominated pattern (CCRI41 and CCRI49 combination) mainly delivers CTK and ABA from roots. In the present study, we observed the anatomy of scion hypocotyls of both patterns under K deficiency (0.03 mmol L–1), and evaluated if it is associated with the flux of CTK and ABA in xylem. In terms of I type grafts (one scion grafted onto one rootstock) of shoot-dominated pattern, the anatomy of scion hypocotyl was clearly influenced by rootstocks, which is inconsistent with the fact that the delivery rate of CTK and ABA in scion xylem was mainly affected by shoot. For Y type grafts (two scions grafted onto one rootstock) of shoot-dominated pattern, the scion with greater CTK flux and lower ABA flux showed growth superiority as compared with its counterpart. However, the two processes referring to flux of phytohormone in scion xylem and scion growth likely occurred concomitantly but not causally. As the results of CTK and ABA flux in scion xylem, the anatomy of scion hypocotyls of root-dominated pattern was obviously altered by root-stock in I grafts. Nevertheless, they might be also concomitant processes rather than the relationship of cause and effect. Addition-ally, there were significant differences in anatomy between two different scions of Y grafts of root-dominated pattern, which was disagreement with the similar CTK and ABA flux in xylem of two scions. In conclusion, the scion hypocotyl anatomy of either shoot- or root-dominated pattern regarding cotton leaf premature senescence induced by K deficiency is independent of CTK and ABA flux in its xylem. In addition, the differences in scion hypocotyl anatomy between two cultivars in I graft type were incon-sistent with those in Y graft type, which is possibly due to shoot-shoot interaction in Y graft.
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