Environmental physiology of wild Ricinus communis L. in Sri Lanka.
Item
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Title
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Environmental physiology of wild Ricinus communis L. in Sri Lanka.
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Identifier
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AAI9530927
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identifier
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9530927
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Creator
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Weerasuriya, Suresh Manitha.
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Contributor
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Adviser: Dwight T. Kincaid
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Date
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1995
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Ecology | Biology, Plant Physiology | Biology, Botany
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Abstract
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Ecophysiological experiments were performed on wild castor (Ricinus communis L.) with the goal of understanding ecotypic differentiation and phenotypic plasticity in this tropical weed. Field and laboratory studies were performed on castor from self-perpetuating wild populations in three Sri Lankan ecosystems: dry shrubland (DS), lowland tropical rainforest (LTR) and wet coastal halophytic zone (WCH). In the field, measurements were made of net photosynthetic rate (P{dollar}\sb{lcub}net{rcub}{dollar}), leaf specific mass (LSM), and leaf stomatal density. Average values for P{dollar}\sb{lcub}net{rcub}{dollar} were 26.6, 23.5, and 21.1 {dollar}\mu{dollar}mol m{dollar}\sp{lcub}-2{rcub}{dollar}s{dollar}\sp{lcub}-1{rcub}{dollar} for castor leaves in the DS, LTR, and WCH sites, respectively. Net photosynthesis was significantly different (F = 57, df = 2,362, P {dollar}<{dollar} 0.0001, R-sq. = 0.14) among the three ecosystems in two-way analysis of covariance with site and time-of-day as main effects and photosynthetically active radiation, air temperature and vapor pressure deficit entered as covariates. Leaves in each ecosystem had similar diurnal trends for P{dollar}\sb{lcub}net{rcub}{dollar}. There was no midday stomatal closure and stomatal density was conserved about a grand mean of 202 mm{dollar}\sp{lcub}-2{rcub}{dollar}. Leaf specific mass was significantly different among the sites, varied over 3-fold, did not overlap between DS and WCH leaves, and averaged 48.9, 39.6, and 27.2 {dollar}\mu{dollar}g dry weight mm{dollar}\sp{lcub}-2{rcub}{dollar} of adaxial leaf surface area for DS, LTR, and WCH, respectively. Average P{dollar}\sb{lcub}net{rcub}{dollar} increased with increasing LSM.;Photosynthetic rates for plants in the common garden in New York, averaged 23.2 {dollar}\mu{dollar}mol m{dollar}\sp{lcub}-2{rcub}{dollar}s{dollar}\sp{lcub}-1{rcub}{dollar} for DS, 20.9 for LTR and 17.7 for WCH plants; trends comparable to field data. Leaf chlorophyll content of WCH plants (19.5 {dollar}\mu{dollar}g/cm{dollar}\sp2{dollar}) was significantly lower on average than for DS plants (21.2) and LTR plants (22.4). Photosynthetic light curves for these plants revealed genetically determined differences among the plants from the three ecosystems. Leaf specific mass of LTR plants (26.8 {dollar}\mu{dollar}g mm{dollar}\sp{lcub}-2{rcub}{dollar}) was significantly higher than DS (20.6) and WCH plants (22.5) but LSM was homogeneous between plants of DS and WCH. Results from drought experiments indicate a possible physiological trade-off among wild castor from different ecosystems for carbon gain under optimal conditions versus under drought conditions. In the glasshouse, xylem water potential was not statistically significantly different among the plant types (pre-dawn mean {dollar}-{dollar}0.25, midday {dollar}-{dollar}0.77 MPa) but temporary wilting point was different at {dollar}-{dollar}0.93 for DS, {dollar}-{dollar}1.1 for LTR, and {dollar}-{dollar}1.2 MPa for WCH plants. This study provides substantial evidence to classify wild castor from the three ecosystems as ecotypes.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
