期刊
TREES-STRUCTURE AND FUNCTION
卷 26, 期 2, 页码 459-468出版社
SPRINGER HEIDELBERG
DOI: 10.1007/s00468-011-0606-2
关键词
Carbohydrates; Coffea arabica; Photosynthesis down-regulation; Photoinhibition; Stomatal conductance; Vapour pressure deficit
类别
资金
- Foundation for Research Assistance of the Minas Gerais State, Brazil [CAG APQ-3995-3.08/7]
- National Council for Scientific and Technological Development, CNPq [301313/2007-5]
- Brazilian Federal Agency
- CNPq
It has long been held that the regulation of photosynthesis in source leaves may be controlled by carbohydrates. The mechanisms that govern the diurnal fluctuation of photosynthesis and the potential role of feedback regulation by carbohydrates during photosynthesis in coffee (Coffea arabica) leaves were investigated in three independent and complementary experiments. An integrative approach using gas exchange measurements in addition to carbon isotope labelling and steady-state carbohydrate and amino acid analysis was performed. Canonical correlation analysis was also performed. In field-grown plants under naturally fluctuating environmental conditions (Experiment I), the overall pattern of gas exchange was characterised by both low stomatal conductance (g (s)) and net carbon assimilation rate (A) in the afternoon; no apparent signs of photoinhibition were observed. Under conditions of low air evaporative demand (Experiment II), only slight decreases (similar to 20%) in A were observed at the end of the day, which were associated with a reduction (similar to 35%) in g (s). For both conditions, any increase in carbohydrate and amino acid pools over the course of the day was small. In leaves from girdled branches (Experiment III), a remarkable decrease in A and particularly in g (s) was observed, as were increases in starch but not in hexoses and sucrose pools. Furthermore, the rate of (CO2)-C-14 uptake (assessed under saturating CO2 conditions) and the partitioning of recently fixed C-14 were not affected by girdling. It is proposed that the diurnal oscillations in A and the differences in A in leaves from girdled and non-girdled branches were merely a consequence of diffusive limitations rather than from photochemical constraints or direct metabolite-mediated down-regulation of photosynthesis.
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