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Abstract Detail


Photosynthesis(Carbon)

Hozain, Mohd [1], Salvucci, Michael E [2], Holaday, A. Scott [3].

Photosynthetic response to moderate heat stress for a temperate and boreal Populus species.

The objective of our study is to elucidate the mechanism that constrains photosynthesis for Populus species under moderate heat stress using two species adapted to contrasting thermal environments. Populus deltoides and P. balsamifera seedlings were grown in 41-L pots in a greenhouse at 25/17 oC (day/night). Rates of CO2 assimilation (A) in photorespiratory conditions were collected at 27, 36 and 40 oC. Above 27 oC, a decline in A occurred for both species. However, at 36 oC, A for P. deltoides was reduced by only 14.0%, whereas A for P. balsamifera was reduced by 28.3 %. Under non-photorespiratory conditions, increasing pCO2 increased A for both species at 36 and 40 oC. A-Ci curves indicated that when temperature increased from 27  to 36 oC, values of maximum carboxylation increased 100% (P. deltoides) and 42% (P. balsamifera) and the RuBP regeneration capacity mediated by the maximum rate of electron transport increased 25% (P. deltoides) and 33.5% (P. balsamifera), whereas a significant reduction in carboxylation efficiency occurred for both species. Preliminary measurements of minimal chlorophyll fluorescence of dark-acclimated leaf discs indicated that the species do not differ with respect to the temperature (~45 °C) at which fluorescence rises as a result of a phase change of thylakoid membrane lipids. Taken together, these data support our hypothesis that the inactivation of Rubisco and not electron transport factors is the major constraint of poplar photosynthesis between 27 and 40 oC.


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1 - Texas Tech University, Biological Sciences, Flint and Main St., Lubbock, Texas, 79409-3131, USA
2 - USDA-ARS
3 - Texas Tech University, Biological Sciences

Keywords:
heat stress
Photosynthesis
rubisco
Populus.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P13015
Abstract ID:2202


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