Initiation of reproductive primordia in Pinus taeda L. relative to soil water stress
1968
Dewers, Robert S.
Adequate available soil water throughout the growing season does not appear to be conducive to a high potential cone crop. A timing of soil water stress seems to favor initiation of ovulate primordia during a yet undefined critical period in the latter part of the growing season. Forty high cone producing ramets in an eastern Texas loblolly pine seed orchard were subjected to combinations of irrigation and drought treatments during the 1967 growing season (April through September) to determine possible effects on the conelet crop the following spring. Water regimes in the deep sands were characterized by water tension curves and neutron scattering measurements of water in the root zone. Treatments under irrigation maintained levels near field capacity while stress treatments had less than 50% field capacity levels after July 15 and depletion continued to near the wilting range on September 30. Covariance analysis and orthogonal comparisons were used to test difference of adjusted treatment means. Trees subjected to 6 months irrigation did not display a significant increase in megasporangeate strobili, but the treatment may have contributed to a high microsporangeate cone crop. Trees subjected to 3 months irrigation followed by 3 months drought produced a significantly higher conelet crop than the treatment subjected to natural rainfall or any of the other treatments. ...
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