Water relations, gas exchange, and early growth rates of outcrossed and selfed Pinus banksiana families

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Abstract
Seedlings of six outcrossed jack pine (Pinus banksiana Lamb.) families from a diallel cross of jack pine were mainly larger than those of three selfed families at the time they were tarnsplanted to the field in Ontario. Outcrossed families also exhibited a greater absolute and relative (percent) growth in total dry matter at the end of the first growing season. Outcrossed families exhibited a higher net photosynthesis, a lower transpiration rate, and a higher water use efficiency on hot, but not mild, days in mid-August. Stomatal conductance, transpiration rate, and net photosynthesis were greater in outcrossed families in September. There were significant, positive correlations between stomatal conductance, transpiration rate, and shoot and root growth in August and September. The results suggest that maintenance of a higher stomatal conductance and net photosynthesis until late in the growing season may contribute to the faster growth rates observed in outcrossed families.
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