Abstract
Relative performance of loblolly pine seedlings and in vitro tissue culture plantlets from four genetic families (two from southeast Texas and two from central Texas) was determined. Growth of root collar diameter, height and leaf area growth, survivability, root/shoot biomass ratio and root system architecture, and physiological attributes such as predawn and diurnal water potential, stomatal conductance and transpiration were investigated. Two adjacent sites in Cherokee County, Texas, were established. Site I was planted with seedlings and plantlets from central Texas which were measured for growth and survival. Site II, planted with seedlings and plantlets from all four families, were observed for all variables. Both sites were established as split-plots. Data were collected through the 1994 and 1995 growing seasons. Seedlings grew considerably more than plantlets in both growing seasons. Survival for all trees exceeded 85% on Site I and 90% on Site II. Trees from central Texas survived better than those from southeast Texas, albeit with negligible differences. Predawn and diurnal water potential was lower for plantlets than for seedlings. Stomatal conductance for plantlets was higher than for seedlings, however stomatal conductance never ceased for either stock type, even when water potential went below-2.0 MPa. During these periods of stress, seedling conductance decreased by a greater percentage than plantlets. Transpiration increased daily from and early morning minimum in all trees, and was higher for plantlets at all measurement times. Plantlet root/shoot biomass ratio was higher than that of seedlings. Higher root/shoot biomass ratio with higher water stress in plantlets was explained by their root system architecture. Plantlets grow a more dichotomous or fibrous root system, whereas seedlings had a herringbone-like structure which can penetrate deep in the soil for a given root length and exploit more soil water.
Rahman, Mohd S. (1997). Performance of loblolly pine (Pinus taeda L.) seedlings and in vitro plantlets on an east Texas site. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1997 -THESIS -R34.