PHYSIOLOGICAL R ESPONSES O F Vismia guianensis TO C ONTRASTING L IGHT ENVIRONMENTS

Resumo

Changes in growth, biomass allocation patterns and CO2 exchange were investigated in Vismia guianensis (Aubl.) Choisy, a medium tree known to invade forest gaps, active pastures and abandoned agricultural areas in Brazilian Amazonia. Plants were grown in controlled environment cabinets, under high (800-1000 μmol m -2 s -1 ) and low (120-200 μmol m -2 s -1 ) Iight regimes, during a 60-day period. No significant differences in CO2 assimilation could be detected between high-light and low-light grown plants in the light response curve. However, dark respiration was higher on high-light grown plants. Relative growth rates were initially similar between light regimes, becoming higher for high-light at the subsequent harvests. Leaf area per unit dry mass of whole plant and leaf area per unit of leaf dry mass were higher for low-light grown plants. The proportion of biomass allocated to leaves was similar between treatments, while root matter per plant dry matter was 15 % higher for high-light and stem matter per plant dry matter was 13 % higher for low-light grown plants. These results suggest that the differential responses of this species to light conditions may contribute to or detract from its ability to succeed in natural and agricultural environments or to respond to weed control strategies. Additional index terms: Biomass allocation patterns, growth analysis, photosynthesis, Amazonia.

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Palavras-chave

• Vismia guianensis
• light environment
• high light
• low-light conditions
• biomass allocation
• relative growth rate
• carbon assimilation
• dark respiration
• leaf area
• root allocation
• weed control
• Amazonian trees
• forest gaps

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