Boron requirement for vegetative growth of Sacha inchi (Plukentia volubilis L.)

Abstract

Sachi inchi is a useful traditional plant in South America that has recently gained notoriety as a nutritional food crop and hence is being cultivated outside its native range. In Thailand, the crop is being grown on soils where boron (B) may be limiting to growth. To determine the response of early vegetative growth of sacha inchi to B supply, to identify B deficiency symptoms, and to define leaf B concentrations for optimum growth. The two experiments were conducted in sand-culture pot arranged in a randomized complete block design with three independent replications. Plants were grown in the preliminary experiment consisted of complete nutrient solution and complete nutrient solution without B. The main experiment was continued by growing plants in the five series of B rate (0, 2.5, 5.0, 7.5 and 10.0 µM B). Plant growth parameters were recorded and B concentration in different plant parts were analyzed. B deficiency strongly inhibited root and shoot development causing stunting and organ malformation. In a sand-culture experiment, maximum growth was obtained with 7.5 µM B and 10 µM B reduced growth. Leaf B concentration of 27–29 mg kg−1 was associated with 90% of maximum vegetative yield. Symptoms of B deficiency and the foliar B concentrations are useful for extension workers and producers looking to improve the productivity of sacha inchi on nutrient poor soils.