Physiological responses of two tropical weeds to shade: II. Leaf gas exchange and nitrogen content

Pesquisa Agropecuária Brasileira

Moacyr Bernardino Dias-filho¹ 

[1] ,Embrapa Centro de Pesquisa Agroflorestal da Amazônia Oriental Belém PA ,Brazil

关键词: photosynthesis;    leaf nitrogen;    Amazonia;    Ipomoea asarifolia;    Stachytarpheta cayennensis;    fotossíntese;    nitrogênio foliar;    Amazônia;    Ipomoea asarifolia;    Stachytarpheta cayennensis;   

DOI  :  10.1590/S0100-204X1999000600005

来源: SciELO

【 摘 要 】

Ipomoea asarifolia (Desr.) Roem. & Schultz (Convolvulaceae) and Stachytarpheta cayennensis (Rich) Vahl. (Verbenaceae), two weeds found in pastures and crop areas in the Brazilian Amazonia, Brazil, were grown in controlled environment cabinets under high (800-1000 µmol m-² s-¹) and low (200-350 µmol m-² s-¹) light regimes during a 40-day period. The objective was to determine the effect of shade on photosynthetic features and leaf nitrogen content of I. asarifolia and S. cayennensis. High-irradiance grown I. asarifolia leaves had significantly higher dark respiration and light saturated rates of photosynthesis than low-irradiance leaves. No significant differences for these traits, between treatments, were observed in S. cayennensis. Low-irradiance leaves of both species displayed higher CO2 assimilation rates under low irradiance. High-irradiance grown leaves of both species had less nitrogen per unit of weight. Low-irradiance S. cayennensis had more nitrogen per unit of leaf area than high-irradiance plants; however, I. asarifolia showed no consistent pattern for this variable through time. For S. cayennensis, leaf nitrogen content and CO2 assimilation were inversely correlated to the amount of biomass allocated to developing reproductive structures. These results are discussed in relation to their ecological and weed management implications.

【 授权许可】

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