Carbohydrate Distribution in Dormant <i>Populus</i> Shoots and Hardwood Cuttings

Abstract

Abstract Stems from two hybrid Populus clones were collected from September to May to determine the effect of harvest date and sampling position on carbohydrate availability. Total sugars increased to a December maximum of 25 percent of dry weight in the shoot tip, then declined through early spring. Raffinose concentrations increased to 7 percent and stachyose to 6 percent of dry weight in December; less than 0.2 percent of both sugars were present in September and May. Sucrose levels were highest in early March, up to 10 percent of dry weight. Concentrations of fructose, glucose, myo-inositol, and melibiose remained less than 1 percent of dry weight during the entire year. Maximum starch content of 7 percent was measured in clone 5262 in early October and 12 percent in clone 5334 in early September. Total carbohydrates ranged from 4.3 to 27.2 percent of dry weight, with significantly lower levels in September and May. Concentrations of sugars and starch were significantly greater at upper shoot positions. Total quantities of sugars and starch were greatest in the larger basal stem sections, and thus in cuttings harvested from lower shoot positions. Starch content was higher and sugar content lower in hardwood cuttings stored at 2° and -3° for 5 to 7 months, when compared with cuttings stored at - 10° and -20°. During storage and soaking, interconversions occurred between starch and sugars, and among sugars. Forest Sci. 30:999-1010.