Superior growth potential in trees: What is its basis, and can it be tested for at an early age?

Abstract

Inherently rapid growth in black spruce (Piceamariana (Mill.) B.S.P.) and radiata pine (Pinusradiata D. Don) could be characterised at a relatively early age (e.g., 3–6 months from germination) by growing progeny of family crosses in near-optimal phytotron or glasshouse environmental conditions. This observation was retrospective in nature, in that the studies of very early performance utilized stored seed from families that had been already tested to age 10+ years in field progeny trials. The very early traits that show the most significant family correlation with the field performance (height or stem volume) are total height, height growth, stem volume, or stem dry weight. The possibility that inherently rapid growth in trees may be causally related to concentration of endogenous plant hormones of the gibberellin class is discussed in relation to the recent finding (S.B. Rood, R.I. Buzzell, L.N. Mander, D. Pearce, and R.P. Pharis. 1988. Science (Washington, D.C.), 241: 1216–1218.) that heterotic growth (hybrid vigour) in maize was strongly related to the concentration of gibberellin A1 (a shoot growth effector in maize) and gibberellin A19 (a precursor to gibberellin A1). Preliminary evidence, based on analysis of hybrid and parental poplar tissue, and on the positive and significant growth response of black spruce slow-growing families (but not fast-growing families) to applied gibberellin (A4/7 mixture), supports the possibility that rapid-growing conifer families may have near-optimal (high) concentrations of endogenous gibberellins, and conversely, that some slow-growing families, at least, may have lower endogenous gibberellin concentrations.