Correlation between early root production, carbohydrate metabolism, and subsequent biomass production in hybrid poplar

Abstract

The relationship between the rooting patterns of five poplar hybrids and stem carbohydrate dynamics was investigated to determine if the availability or metabolism of carbohydrates was limiting early root production of cuttings. Differences in early root production (i.e., number, length, and dry weight) after 17 days paralleled the subsequent differences in accumulation of aboveground biomass that were observed when two Populus balsamifera L. × deltoides Bartr. (Jackii 4 and Jackii 7) and three Populus deltoides Bartr. × nigra L. (DN 2, DN 22, and DN 15) hybrids were compared. Total root length and dry weight of Jackii 4 was four times that of Jackii 7. Both DN 2 and DN 22 had a total root length twice that of DN 15. Rooting characteristics may be useful criteria for selection of productive clones. Carbohydrate analysis of stem cuttings suggested that hybrids differing in biomass production displayed different patterns of carbohydrate utilization. The concentrations of glucose and myoinositol declined more in faster growing hybrids (Jackii 4, DN 2, DN 22) than in slower growing hybrids (Jackii 7, DN 15). The results suggest that faster growing hybrids consume monosaccharides in growth processes, whereas the slower growing hybrids convert monosaccharides into alternative storage forms and use less in growth processes. The initial myoinositol concentration in stem cuttings of poplar hybrids was correlated (r2 = 0.95) with root dry weight produced after 17 days, but the initial starch concentration was unrelated to later root biomass production. The results suggest that initial myoinositol concentration in cuttings may be used in early selection for rooting performance.