THE EFFECTS OF POTASSIUM APPLICATIONS ON DROUGHT STRESS IN SUGAR BEET: PART I. SUGAR BEET QUALITY COMPONENTS

Abstract

This is the first in a series of papers describing the effects of potassium applications on drought stress in sugar beet. Drought stress is the stress to which there is the most exposure in agricultural areas. In this research, the effect of potassium applications under drought stress on some quality parameters of sugar beet, which is a strategic plant, was investigated. In the experiment, irrigation levels were kept at 33%, 66% and 100% of field capacity. Different doses (10-20-40-80 mg kg-1) of potassium were applied to the plants. The plants were grown in the growth chamber under controlled conditions (day/night 16/8 hours, 25/15 0C, 60-70% humidity). A comparison of the plants irrigated at the level of 100% of the field capacity and stressed plants showed that the root sugar content decreased by 53.18% and 65.1%, and shoot sugar content by 20.8% and 17.8% respectively at 66% and 33% irrigation levels. Root white sugar content (58.61 mg g-1) was obtained at the dose of 10 mg kg-1 potassium level, while the lowest (32.61 mg g-1) was obtained at the dose of 80 mg kg-1 potassium level. Shoot protein content has increased significantly with an increasing level of potassium under drought (33% and 66%) condition. The root α-amino nitrogen content decreased under drought stress with increasing potassium concentrations while it increased in non-stressed plants. According to the results obtained from the experiment, the potassium applied to the plants under drought stress led to the increase of the root sugar, root white sugar content and shoot protein content the reduction of root α-amino nitrogen content. Therefore, it can be said that potassium may play a critical role in reducing the negative effect of drought stress in sugar beet.