Greenhouse growth of Pinus x rigitaeda seedlings in response to water stress and correlations with 7 year plantation performance

Abstract

Seedlings of two P. rigida and four P. taeda families and six P. x rigitaeda crosses were grown in a greenhouse under two moisture regimes. Water stress decreased growth in every case in every variable measured. Water stress also elicited some genetic differences in the pitch pine and loblolly pine that were not apparent under the non-stressed treatment. The major differences between pitch and loblolly seedlings seemed to be primarily a function of large differences in seed size. Free growth may also play a major role in differences between the two species.

The theory that allometric coefficients are a good indicator of growth under moisture stress was not substantiated by this experiment. In addition, k-values were found to remain relatively constant despite changes in moisture stress.

It appears that genetic variance components in P. x rigitaeda may have importance under one set of environmental conditions, and be unimportant in another. Inter-relationship of crosses and confounding of genetic expectations, however, make it difficult to speculate which variance components are most important under moisture stress. Correlations were made between seedling growth characteristics and 1, 2, 3, 4, 5 and 7 year height and a 7 year volume index. Many significant correlations were found with 7 year height and volume. These correlations indicate that greenhouse experiments may be useful as an early genetic screening technique in P. x rigitaeda.