Seedling shoot growth of loblolly pine families under two nitrogen levels as related to 12-year height

Abstract

Seedling shoot elongation and biomass were examined for 23 open-pollinated loblolly pine (Pinustaeda L.) families grown in a greenhouse under two nitrogen regimes. Significant genetic variation was detected among families for the number of growth cycles, total seedling height, cyclic-growth elongation, the number of stem units, and biomass of stem free growth, cyclic growth, total stem, needles, and total shoot. Heritability estimates were generally high for shoot characteristics except for mean stem-unit length. Shoot biomass measures were weakly or negatively correlated with 12-year-height performance. Elongation of cyclic growth, number of growth cycles, and number of stem units showed stronger correlations with field performance than did seedling height. Juvenile–mature correlations were higher for the low nitrogen treatment, suggesting that 12-year height of loblolly pine families can be more accurately predicted when the seedlings are grown under greenhouse conditions that mimic field nitrogen levels.