| Chlorine is the essential trace element of the higher plants and has many nutritional functions for plants. Many previous studies studied the effects of potassium uptake through high concentrations of Na+ and Cl- under the conditions of salt stress and less to explore the nutritional physiological function of Cl-. Against this background, this article studied the effects of chloride on the potassium transfer and the growth of rice seedlings to provided the theoretical basis for the chloride’s physiological function of plant nutrition. Yangdao 6 and Huaidao10 were used as the experimental materials in this thesis to explore the effects of chloride on growth and root morphology of rice seedlings, and the effects on potassium uptake through ion uptake kinetics, ion flux and membrane potential measurements. The results of the study were as follows:(1) Chloride could promote the growth of rice seedlings. Compared with gluconate,1 mmof L-1 C1- increased the fresh weight and height of rice seedlings, but the impact on root/shoot ratio was not significant. C1- increased the contents of N, P and K of rice seedling in overground part.(2) C1- increased the total length of rice seedlings roots, but had little effect on the root surface area and root volume. C1- increased the length of Yangdao6’s thick roots, while increased Huaidao10’s fine roots.(3) C1- channel inhibitors (Zn2+, NA, DIDS) significantly reduced the absorption rate of C1- by rice seedlings. DIDS showed the highest inhibitory rate under the conditions of 0.2 mmol·L-1 C1-. And there was no differences among the three inhibitors when supplied 2 mmol·L-1 C1-. The uptake rate of K+ had no significant differences between KC1+DIDS treatment and KGlu treatment. Therefore, the impact of DIDS on rice seedlings K+ uptake was caused by inhibiting the chloride channel. Zn2+ and NA not only inhibited the activity of chloride channels, but also had influence on K+ uptake.(4) Potassium uptake kinetics experiments showed that, at the concentration with less than 2 mmol·L-1 KC1, K+ uptake rate was still consistent with the description of the Michaelich-Menten equation after adding C1- channel inhibitor DIDS. Adding DIDS did not reduce K+ maximum uptake rate Vmax, but increased Km value. Compared with Glu- treatment, C1- treatment showed similar Vmax, but lower Km value. This meant, the positive effect of C1- (≤ 2 mmol· L-1) on potassium uptake mainly led from the increase of affinity between potassium transmembrane transfer system, rather than from the increase of Vmax.(5) With the NMT technology K+ flux velocity on root surface of rice seedling under the conditions of 0.15 mmol·L-1 and 1 mmol·L-1 KC1 was explored and the results also showed that C1-could increase the rate of K+ uptake. With 0.15 mmol·L-1 KC1, adding NEM led to K+ efflux from roots, and adding DIDS increased K+ efflux. With lmmol · L-1 KC1, after adding TEA to inhibit potassium channels, rice still kept K+ uptaking through NSCCs and DIDS could reduce the net K+ uptake rate. It showed that, under the condition of low KC1, C1- reduced the K+ efflux of NSCCs, while under high KC1, C1- promoted K+ uptake of potassium channel.(6) Glass microelectrode technique was used to explore the response of transmembrane potential differences to C1- under 1 mmol·L-1 K+ conditions.1 mmol·L-1 KC1 or 1 mmol·L-1 KGlu caused depolarization of transmembrane potential first and then gradually restored to near original resting membrane potential. Depolarization degree of KC1 treatment was higher than that of KGlu treatment. After inhibiting potassium channels with TEA, the membrane potential showed a slow hyperpolarization response to lmmol·L-1 KC1 and 1mmol·L-1 KGlu. Under the condition of 1 mmol·L-1 K+, compared with Glu-, C1- reduced the hyperpolarization degree of membrane potential in the K+ uptake process with NSCCs, and increased the depolarization degree in the total process of K+uptake.(7) Levels of pH and Na+ in media affected the relationship between C1- and K+ uptake by rice seedlings roots. The inhibitory rate of DIDS on potassium uptake changed with pH and reached highest at pH4.1 mmol·L-1 Na+ promoted the potassium absorption by Huaidao10, but had little effect on the Yangdao6. For DIDS treatments, the existence of Na+ had no significant impact on potassium uptake rate.1.0 mmol·L-1 Na+ had no effect on potassium uptake by rice seedling suppressed chloride channel. This indicated that the positive effects of 1.0 mmol·L-1 Na+ on K+ uptake of rice seedlings was related to the activity of chloride channels. |
