Growth characteristics and soluble carbohydrate concentrations of containerized eastern white pine seedlings

This study investigated relationships between growth characteristics and soluble carbohydrate concentrations of 10-month old eastern white pine (Pinus strobus L.) seedlings grown in four different greenhouse environments: (1) augmented photoperiod and ambient carbon dioxide, (2) augmented photoperiod and supplemental carbon dioxide, (3) continuous photoperiod and ambient carbon dioxide, and (4) continuous photoperiod and supplemental carbon dioxide. Within each of these environments, four different media were used in two rootrainer sizes with each rootrainer tray further divided such that 50 percent received foliar mist fertilization. Root collar diameters, heights, root fresh weights, root dry weights, top fresh weights, top dry weights, leaf dry weights, stem dry weights, total fresh weights, total dry weights, and root/shoot ratio were recorded. Total soluble sugars, ketose sugars, and reducing sugars were determined for leaf, stem, and root tissues and for the total seedlings.

Continuous photoperiod increased all growth characteristics, except height, by 20-25 percent. Ketose and reducing sugar concentrations in stem tissue were least in seedlings grown in continuous light. Enriched carbon dioxide environments produced larger seedlings (20-25 percent) than those grown under ambient environments and also resulted in significantly higher total sugar and ketose sugar concentrations within root tissue. Pine bark-vermiculite and Redi-Earth media were superior for promoting diameter, height, and biomass growth. Soluble sugar concentrations were approximately 25 percent greater within seedlings grown in Redi-Earth medium. Seedlings in Hillson rootrainers had larger diameter, height, and biomass (5 percent, 25 percent, and 25 percent, respectively). Foliar mist fertilization showed very little effect on seedling growth and no effect on sugar concentrations.

Leaf soluble carbohydrate concentrations were positively correlated with height, root collar diameter, and root growth; whereas, root soluble sugar concentrations were positively correlated with top growth and root collar diameter growth. Soluble carbohydrate concentrations within stem tissue were negatively correlated with biomass growth.

Greenhouse environments can be manipulated to produce desired seedling growth characteristics and seedling soluble carbohydrate concentrations by extending the photoperiod, increasing the carbon dioxide atmospheric concentration, and using Redi-Earth growing medium in Hillson rootrainers.