HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Aragão, D. V. Articles by de Carvalho, C. J. R. Search for Related Content PubMed Articles by Aragão, D. V. Articles by de Carvalho, C. J. R. Agricola Articles by Aragão, D. V. Articles by de Carvalho, C. J. R.

Correlation but no causation between leaf nitrogen and maximum assimilation: the role of drought and reproduction in gas exchange in an understory tropical plant Miconia ciliata (Melastomataceae)¹

²Universidade Federal Rural da Amazônia, Departamento de Ciências Florestais, Av. Presidente Tancredo Neves, n°2501—Bairro Terra Firme—Caixa Postal 917. CEP 66077-530—Belém—Pará—Brazil; ³School of Forest Resources and Conservation, Institute of Food and Agricultural Sciences, University of Florida, P.O. Box 11070, Gainesville, Florida 32611-0760 USA; ⁴Department of Botany, College of Liberal Arts and Sciences, University of Florida, P.O. Box 118526, Gainesville, Florida 34002-8526 USA; ⁶Laboratório de Ecofisiologia e Propagação de Plantas, Empresa Brasileira de Pesquisa Agropecuária—Amazônia Oriental, Trav. Dr. Enéas Pinheiro S/N—Bairro Marco—Caixa Postal 48. CEP 66092-100—Belém—Pará—Brazil

Alternative hypotheses were tested to explain a previously reported anomaly in the response of leaf photosynthetic capacity at light saturation (A_max) in Miconia ciliata to dry-season irrigation. The anomaly is characterized by an abrupt increase in leaf A_max for nonirrigated plants at the onset of the rainy season to values that significantly exceeded corresponding measurements for plants that were irrigated during the previous dry season. Hypothesis 1 posits that a pulse in leaf nitrogen increases CO₂ assimilation in nonirrigated plants at the onset of the wet season and is dampened for irrigated plants; this hypothesis was rejected because, although a wet-season nitrogen pulse did occur, it was identical for both irrigated and nonirrigated plants and was preceded by the increase in assimilation by nonirrigated plants. Hypothesis 2 posits that a reproduction-related, compensatory photosynthetic response occurs in nonirrigated plants following the onset of the wet season and is dampened in irrigated plants; consistent with hypothesis 2, high maximum assimilation rates for control plants in the wet season were significantly correlated with fruiting and flowering, whereas irrigation caused flowering and fruiting in the dry season, spreading M. ciliata reproductive activity in irrigated plants across the entire year.

Key Words: Amazon • compensatory photosynthesis • drought seasonality • nitrogen content • reproductive phenology • secondary forest