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- Author or Editor: D. C. Morgan x
Trees of apple cv. Gala (Malus domestica Borkh.), which had previously been dormant pruned, were pruned in mid-December (early summer pruned—73 days after full bloom), mid-January (late summer pruned—108 days after full bloom), or were only dormant pruned (control). On 2 harvest dates (late February and early March) fruit from 4 different regions of the tree canopy were assessed for red blush, background color, soluble solids concentration, and fresh weight. Penetration of photosynthetic photon flux density (PPFD) to each region was measured at the summer pruning times and at the First harvest. Summer pruning increased the percentage of red blush—but not background color—for both pruning dates, decreased fresh weight of fruit from the early pruned trees, and decreased the soluble solids concentration of fruit from the late-pruned trees. The percentage of red blush and fruit fresh weight both showed a highly positive correlation with PPFD penetration, but for fruit fresh weight, the correlation also was dependent on the pruning treatment. The concentration of soluble solids also was related to PPFD penetration although, in comparison with fresh weight, the differences were reduced. Background color was relatively independent of tree position or pruning treatment.
Plants of lettuce (Lactuca sativa L. cv. Grand Rapids), spinach (Spinacia oleracea cv. Bouquet), white mustard (Sinapis alba L.), and wheat (Triticum aestivum L. cv. Karamu) were grown at 2 photosynthetic photon flux densities (PPFD 400 to 700 nm at 320 and 700 μmol s−1m−2 under 4 lamp treatments: metal halide lamps alone, high-pressure sodium lamps alone, metal halide plus tungsten halogen lamps (ca. 1:1 installed wattage), and metal halide plus high-pressure sodium lamps (ca. 1:1 installed wattage). Plants of all species grew well under all treatments and no growth abnormalities were apparent at harvest. It is concluded that dry-weight increase was determined by PPFD and not by spectral irradiance. However, lettuce, spinach, and mustard hypocotyl elongation was greater in young plants grown under the high-pressure sodium lamps in comparison with those grown under the metal halide or metal halide plus tungsten halogen treatments. A strong negative relationship between hypocotyl length and blue photon flux density (400–495 nm) was demonstrated. Anthesis of wheat occurred at the same time under all lamp treatments, but anthesis of mustard differed by 2 days at the higher PPFD and 4 days at the lower PPFD among lamp treatments. The time of anthesis for mustard was found to be weakly but positively correlated with the calculated phytochrome photoequilibrium. Chlorophyll concentrations in young lettuce and spinach plants growing under the high-pressure sodium lamps were 55% and 26% lower, respectively, than those in plants growing under metal halide lamps at the high PPFD level. However, final dry weight was unaffected by any of these morphological differences in the early growth stages.
Stem cuttings taken from rooted propagules of a 2-year old South Texas live oak, Quercus virginiana Mill., and maintained for 2 years in a greenhouse rooted in greater numbers than did cuttings taken directly from the original tree 2 years later. Rooting of cuttings from trees 5-8 years decreased with tree age.