Effect of sink on carbohydrate metabolism in stems and roots of the phasey bean (Macroptilium Lathyroides (L.) Urb.) during regrowth

Abstract

AbstractThe objectives of this study were to investigate the changes in the effect of sink on storage carbohydrate content and the relationship between amylase activity and storage carbohydrate content in stems and roots of the phasey bean (Macroptilium lathyroides (L.) Urb.) following defoliation. Plants were grown for 53 days after sowing in pots and then cut at a height of 10 cm. One lateral bud remaining by selective trimming at the cotyledonary node (N0), the second leaf node (N2), or the fourth leaf node (N4) was regrown under dark conditions at 22°C, and new shoot production, carbohydrate content and amylase activity in the stems and roots were measured 0, 1, 3, 6 and 10 days after defoliation. Plants having upper buds produced higher new shoots on day 10 post‐defoliation, indicating that the growth of buds correlated with sink demand and affected dry weight production. Fructose, glucose and sucrose contents decreased in the stems and roots after defoliation and correlated negatively with sink demand especially in the stems. Starch content decreased more than sugar contents in stems and roots, and more considerably in the plants having upper buds (higher sink tissues) especially in stems. Total amylase and α‐amylase activities changed slightly, and α‐glucosidase activity decreased in stems and roots after defoliation. The lack of increase in α‐amylase with the decrease in starch under sink demand indicates that starch content could fluctuate without changes in α‐amylase activity during phasey bean regrowth.