Leaf physiology and fractional dry weight allocation were examined in four
open-pollinated families of loblolly pine (Pinus taeda L.) and slash pine (
Pinus elliottii Englm. var. elliottii) in response to growth under low and
high N supply for six months. Nitrogen greatly influenced dry weight alloca
tion, total mass, leaf net photosynthesis and leaf conductance in seedlings
of both species. Family variation in fine root allocation was observed und
er low but not high N treatment, but for the majority of physiological and
growth traits, family variation was stable under varying N treatment. Famil
y rankings based on juvenile height, diameter and biomass accretion were si
milar to rankings based on field performance at 22 years in slash pine but
not loblolly pine. Lower leaf maintenance respiration rates were associated
with families exhibiting the most rapid juvenile growth.