Differential responses of six Chinese cabbage (Brassica rapa L. ssp pekinensis) cultivars to potassium ion deficiency

作者：Li H Y; Si D X^*; Lv F T

来源：Journal of Horticultural Science & Biotechnology, 2015, 90(5): 483-488.

DOI：10.1080/14620316.2015.11668704

Genotypes of crop species differ in their potassium (K+) efficiency, including K+-uptake efficiency and K+-utilisation efficiency, but we have little knowledge concerning genetic variations in K+-efficiency in Chinese cabbage (Brassica rapa L. ssp.pekinensis). Therefore, we investigated different responses to K-deficiency in six Chinese cabbage cultivars and identified the mechanisms behind the differences. Based on dry matter (DM; g plant(-1)) content and relative DM content under K+-deficiency (as a percentage of their DM content under K-sufficiency), the cultivar 'Defeng 1' was considered K+-efficient and 'Fengkang 70' was considered K+-inefficient. Under low K conditions (0.3 mM), Defeng 1' had a significantly higher plant K+ content and K+-uptake efficiency than 'Fengkang70,' while there was no obvious difference in plant K+-utilisation efficiency. Therefore, the higher K+ efficiency of Defeng 1' resulted mainly from a higher K+-uptake efficiency rather than a higher K+-utilisation efficiency. Although total root lengths, root surface. areas, and root volumes in `Defeng 1' were 1.4-, 1.5-, and 1.5- fold those of 'Fengkang 70', respectively, the proportion of the length of roots of diameter <= 0.2 mm was not significantly different between the two cultivars. Thus, the proportion of fine roots (diameter <= 0.2 mm) was not a key determinant of the efficiency of K+-uptake. Furthermore, the more K+-efficient cultivar 'Defeng 1' had a lower K-m (Michaelis constant; i.e., the K+ concentration in the substrate at which K+-uptake proceeds at half the maximum rate) for K+-uptake and C-mm value (the minimum K+ concentration at the root surface at which the net uptake of K+ is zero), as well as a higher I-max (the maximum K+ uptake rate) under low-K stress, which resulted in a more efficient uptake of K+ ions. These results indicated that K+-efficiencies among the six Chinese cabbage cultivars tested were different, and that the difference lay mainly in K+-uptake efficiency, which was largely due to a better-developed root system, as well as to more efficient K+ ion uptake.

• 出版日期2015-9
• 单位聊城大学