Effect of sucrose supplementation by stem injection on the development of soybean plants

Abstract

Over the past half decade several stem injection methods have been developed for cereal plants. These methods allow researchers to administer solutions to cereal plants to study their effects on plant physiology. However, little work has been done to extend this technique to non-cereals. An experiment was conducted to test an injection technique that could be suitable for soybean plants (Glycine max [L.] Merr.), and to study the effect of long-term injection of sucrose on the growth of soybean plants. An injection setup comprising a supporting stand and a fluid injection system was established. Pressure was applied to the plunger of a 5 ml syringe using ceramic bricks to force test solutions into the plants. Solutions of 0, 150, and 300 g sucrose I−1 were injected into soybean plants for 8 weeks starting at the seedling VC stage. Distilled water had the greatest uptake rate, followed by the 150, and then the 300 g sucrose I−1 solutions. The overall average uptake during the injection period was 77.3 ml. Average sucrose uptake values were 11.8 and 13.5 g per plant for the 150 and 300 g sucrose I−1 treatments. This represented approximately 65% of the total dry weight of the plants. Sucrose injection increased leaf area and pod number relative to the control plants. Nodule numbers were lower for sucrose injected treatments, but their dry weights were higher than the control. Above-soil dry matter was higher for the plants injected with 300 g sucrose I−1 than those injected with water. The injection system tested was able to administer concentrated solutions into soybean plants for most of their period of growth and development. The sucrose supplementation had positive effects on soybean growth but suppressed photosynthesis.