PARENT SESSION
Oral Session #13: Plant Ecology: Light Relationships. Presiding: J. Rebbeck.
Monday, August 6, 2001. 1:00 PM to 4:30 PM. Hall of Ideas P&Q.
Morpho-physiological responses of nine neotropical shrubs to contrasting light and water regimes in Panama.
Cordero, Roberto1,2, Pearcy, Robert1, Wright, Joseph2, Galvez, David2, 1 2
ABSTRACT- We studied the physiological and morphological adjustments of nine neotropical Psychotria (Rubiaceae) shrubs grown in contrasting light and watering regimes in the moist forests of central Panama. We compared twenty-one physiological, architectural, and growth variables collected from plants grown in twelve gardens (six gaps and six understories, half of each treatment watered during two dry seasons). Species were grouped by their habitat preference (a moisture/light preference ranking) and sub-genus ascription to identify ecological and phylogenetic influences on plant performance. Sixteen variables were strongly affected by light treatment, which it was also significant in 18 variables when based on their habitat preference and sub-genus ascription of the species. There was not evidence of irrigation effects in any variable or any species grouping level. The efficiency of PAR absorption (Ea) and the effective leaf area ratio (LARe) were strongly affected by light treatment at the species, habitat preference and sub-genera levels. Ea and LARe were different among species and habitat preferences, but light interception and hydraulic functions were not different between sub-genera. Most architectural variables distinguished between species of different sub-genera and different habitat preference. Species belonging to the Heteropsychotria subgenus had smaller biomass and leaf area, were more slender, and had smaller crowns and higher height growth efficiency than species in the sub-genus Psychotria. Species grouping were distinguished by differences in morphological characters rather differences in either leaf photosynthetic or stem hydraulic functions.
KEY WORDS: ligth interception, hydraulic conductance, Neotropical Psychotria, crown architecture