Morphological and Physiological Responses of Sugar Beet to Alkaline Stress

To explore the morphological and physiological responses of sugar beet to alkaline soils, four levels of alkaline (NaHCO3 + Na2CO3) concentration, including 0.0% (designated as A(0.0%), control), 0.5% (designated as A(0.5%)), 0.7% (designated as A(0.7%)), and 0.9% (designated as A(0.9%)), were applied to sugar beet cultivars KWS0143 and Beta464 in a pot experiment in 2015 and 2016. The growth indexes, osmolyte content, and antioxidase activity of both cultivars were measured. Alkaline stress significantly decreased the emergence rate of both cultivars. Dry matter weight per plant and leaf chlorophyll content first increased but then decreased with increasing alkaline concentration at different stages in both years. The content of leaf osmolytes and the activity of antioxidases were enhanced at A(0.5%) and A(0.7%) but inhibited at A(0.9%). These findings suggested that sugar beet adapted well to alkaline soil stress by osmotic adjustment and antioxidation and that its growth increased when stress was relatively low (A(0.5%) and A(0.7%)) at different stages. Moreover, proline content, CAT activity, and APX activity of KWS0143 under the same treatment were higher than those of Beta464. Our results confirmed that sugarbeet variety KWS0143 was showing tolerant behaviour to alkalinity.