photosynthesis

Spatial and temporal patterns of water quality indicators in reef systems of southwestern Puerto Rico

Otero E.E. Spatial and temporal patterns of water quality indicators in reef systems of southwestern Puerto Rico. Carribbean journal of science, Vol 45, Is 2-3, 2009, pp. 168-180

Acclimation of tropical tree species to hurricane disturbance: ontogenetic differences

Wen, S.Y., Fetcher, N. & Zimmerman, J.K. (2008) Acclimation of tropical tree
species to hurricane disturbance: ontogenetic differences. Tree Physiology,
28, 935–946.

Abstract: 
We investigated acclimation responses of seedlings and saplings of the pioneer species Cecropia schreberiana Miq. and three non-pioneer species, Dacryodes excelsa Vahl, Prestoea acuminata (Willdenow) H.E. Moore var. montana (Graham) Henderson and Galeano, and Sloanea berteriana Choisy ex DC, following a hurricane disturbance in a lower montane wet forest in Puerto Rico. Measurements were made, shortly after passage of the hurricane, on leaves expanded before the hurricane (pre-hurricane leaves) and, at a later time, on recently matured leaves that developed after the hurricane (post-hurricane leaves) from both seedlings and saplings at sites that were severely damaged by the hurricane (disturbed sites) and at sites with little disturbance (undisturbed sites). Pre-hurricane leaves of the non-pioneer species had relatively low light-saturated photosynthetic rates (Amax) and stomatal conductance (gs); neither Amax nor gs responded greatly to the increase in irradiance that resulted from the disturbance, and there were few significant differences between seedlings and saplings. Pre-hurricane leaves of plants at undisturbed sites had low dark respiration rates per unit area (Rd) and light compensation points (LCP), whereas pre-hurricane leaves of plants at disturbed sites had significantly higher Rd and LCP. Post-hurricane leaves of plants at disturbed sites had significantly higher Amax and Rd than plants at undisturbed sites. Compared with seedlings, saplings had higher Amax and Rd and showed greater acclimation to the increase in irradiance that followed the disturbance. Post-hurricane leaves of the non-pioneer species had significantly lower Amax and were less responsive to changes in irradiance than the pioneer species C. schreberiana. Variation in Amax across light environments and stages was strongly related to differences in leaf mass per unit area (LMA), especially in the non-pioneer species. As indicated by Vcmax or Jmax per unit nitrogen, light acclimation of Amax was determined by leaf morphology (LMA) for the nonpioneer species and by both leaf morphology and leaf biochemistry for C. schreberiana. Ontogenetic changes in Amax were attributable to changes in leaf morphology. The ontogenetic component of variation in Amax across light environments and stages differed among species, ranging from 36 to 59% for the non-pioneer species (D. excelsa, 59.3%; P. acuminata var. montana, 44.7%; and S. berteriana, 36.3%) compared with only 17% in the pioneer species C. schreberiana.

Lack of Ecotypic Differentiation: Plant Response to Elevation, Population Origin, and Wind in the Luquillo Mountains, Puerto Rico

Fetcher, Ned; Cordero, Roberto A.; Voltzow, Janice 2000. Lack of Ecotypic Differentiation: Plant Response to Elevation, Population Origin, and Wind in the Luquillo Mountains, Puerto Rico. BIOTROPICA 32(2) :225-234 .

Abstract: 
How important is ecotypic differentiation along elevational gradients in the tropics? Reciprocal transplants of two shrubs, Clibadium erosum (Asteraceae) and Psychotria berteriana (Rubiaceae), and a palm, Prestoea acuminata var. montana (Palmaceae), were used to test for the effect of environment and population origin on growth and physiology in the Luquillo Experimental Forest of Puerto Rico. Two sites were used, one at Pico del Este (1000 m in cloud forest) and one at El Verde (350 m in lower montane rain forest). At the cloud forest site, plastic barriers were erected around a subset of the plants to examine if protection from wind affected survival or biomass accumulation. Survival of C. erosum and P. berteriana was not affected by site, population origin, or the presence of barriers. For P. acuminata var. montana, survival was higher for plants with barriers, but not affected by site and population origin. Plants of C. erosum and P. berteriana at El Verde grew larger than at Pico del Este, but there was no effect of population origin or barrier treatment on biomass accumulation for these species. For P. acuminata var. montana, there was no effect of environment, population origin, or barrier treatment on biomass accumulation. Light-saturated photosynthetic rate (Amax) of C. erosum, P. berteriana, and P. acuminata var. montana, as well as leaf anatomical characteristics of C. erosum, were unaffected by environment, population origin, and barrier treatment. On balance, there seems to be little evidence of ecotypic differentiation in these species along the gradient.
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