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Title: Drought effects on leaf abscission and leaf production in Populus clones
Author: Pallardy, Stephen G.; Rhoads, Julie L.
Publication: In: Pallardy, Stephen G.; Cecich, Robert A.; Garrett, H. Gene; Johnson, Paul S., eds. Proceedings of the 11th Central Hardwood Forest Conference; Gen. Tech. Rep. NC-188. St. Paul, MN: U.S. Department of Agriculture, Forest Service, North Central Forest Experiment Station: 373-383
Abstract: Leaf abscission and foliation responses to water stress were studied in potted plants of five Populus clones grown in a greenhouse. As predawn leaf water potential (Ψ1) fell to -3 MPa, drought-induced leaf abscission increased progressively to 30% for data pooled across clones. As predawn Ψ1 fell below -3 MPa, drought-related abscission was about 50%. When combined with abscission rates in well-watered "phenological control" plants, abscission exceeded 80-90% in the most severely water-stressed plants. Clonal variation in water stress-induced abscission was statistically significant, but appeared to be confounded with clonal differences in leaf loss in control plants. Production of new leaf area ranged from 0 to 1,389 cm². Pooled across clones, maximum production of leaf area occurred in plants previously subjected to moderate water stress (-0.5 to -0.75 MPa). This stimulation of leaf development was associated with greater areas of individual leaves. At predawn Ψ1 < -2 MPa leaf area production was greatly decreased (<120 cm²). Generally, leaf area production during and after water stress did not vary systematically among clones. However, one clone of Populus trichocarpa appeared more capable than others of producing new leaves when severely stressed and allowed to recover. Results indicate substantial sensitivity of Populus clones to leaf abscission under water stress, a capacity for refoliation if water stress does not become severe, and some possibility of genetic variation among clones in these responses.
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