K+ is the most abundant cation in plant cells and plays an important role in many ways.K+ uptake of plant has respect to its salt resistant capacity.There are two categories of channel transportation for plants to uptake K+,one is through K+ channels and the other is through nonselective cation channels(NSCCs).The transmembrane localization of K+ may change membrane potential(MP).In this paper,three wheat varieties with different salt tolerance were selected and the MP was measured by microelectrode during K+ uptake.The results showed that the effects of K+ uptake on MP through K+ channels or NSCCs were distinct.K+ influx through K+ channels led to MP hyperpolarization,while K+ influx through NSCCs resulted in depolarization.Diverse MP alteration of wheat varieties with different salt tolerance was mainly due to NSCCs-mediated K+ uptake.Compared with the salt-tolerant wheat,the MP hyperpolarization during K+ uptake of saltsensitive wheat was much more evident,probably because of the cation outflux through NSCCs during this process.
WANG Yu-qianWANG Xiao-liSHAN Yu-huaSHENG Hai-junFENG Ke
Plants need to be efficient in nutrient management, especially when they face the temporal nutrient defficiencies. Understanding how crops respond to nitrogen (N) starvation would help in the selection of crop cultivars more tolerant to N deficiency. In the present work, the physiological responses of two wheat cultivars, Yannong 19 (YN) and Qinmai 11 (QM), to N starvation conditions were investigated. The two cultivars differed in biomass and N rearrangement between shoots and roots during N starvation. QM allocated more N to roots and exhibited higher root/shoot biomass ratio than YN. However, tissue measurement indicated that both cultivars had similar nitrate content in leaves and roots and similar remobilization rate in roots. Microelectrode measurement showed that vacuolar nitrate activity (concentration) in roots of QM was lower than that in roots of YN, especially in epidermal cells. Nitrate remobilization rates from root vacuoles of two cultivars were also identical. Moreover, vacuolar nitrate remobilization rate was proportional to vacuolar nitrate activity. During N starvation, nitrate reductase activity (NRA) was decreased but there were no significant differences between the two cultivars. Nitrate efflux from roots reduced after external N removal and QM seemed to have higher nitrate efflux rate.
