空心莲子草、大豆和向日葵根部K~+(~(86)Rb~+)的吸收和通量分析

与大豆、向日葵相比,空心莲子草根系具有一个较高效率的K~+吸收机制。它的K_m值很小,I_m值又较高。空心莲子草根系将K~+向地上部运输的能力也比大豆和向日葵高得多。 上述三种植物根组织K~+含量的差异主要是因为液泡中含K~+量的不同,而细胞质的含K~+量影响不大。其中,参数K_cv/K_vc的比值可以表示液泡积累K~+的特征,并且也决定着不同植物根组织积累K~+的能力。

A STUDY OF POTASSIUM ABSORPTION AND COMPARTMENTATION IN ROOTS OF ALTERNANTHERA PHILOXEROIDES (MART.) GRISEB IN COMPAAISON WITH SOYBEAN AND SUNFLOWER SEEDLINGS

The absorption, transport to shoot and compartmentation of potassium werestudied in roots of A. philoxeroides in comparison with soybean and sunflower seed-lings. With remarkably low K_m and high I_m and a great transport rate to shoot,A. philoxeroides possesses more efficient mechanisms of potassium absorption andtransport by roots than those of either soybean or sunflower. The rate constants for unidirectional fluxes through plasmalemma (K_(oc) in-wards or K_(co) outwards) and tonoplast (K_(cv) inwards or K_(vc) outwards) in roots, vary-ing with species, do not correlate apparently with their kinetic parameters of po-tassiun absorption. A. philoxeroides has the lowest K_(co) and K_(vc) among the threespecies, which suggests that potassium is held more firmly by its root cell plasma-lemma than by that of soybean's or sunflower's, and the same is true for tonoplast. The difference in potassium content of root tissues (Q_T) is largely due to thedifference in potassium content of vacuoles (Q_v) which varies with the rate of po-tassium accumulation by vacuoles (J_(cv)), and not that of cytoplasm (Q_c). There-fore, the ratio K_(cv)/K_(vc), which is used to characterize the potassium accumulationin root vacuoles, is found to correlate closely with the ability of root tissues to ac-cumulate potassium, which is to be tested with more plant species.