Interferência de plantas daninhas em características fisiológicas de plantas de mandioca / Weed interference in physiological characteristics of cassava

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The objective of this work was to evaluate characteristics associated with photosynthesis and water use in cassava plants in competition with three weed species. For this, experiments were mounted in open environment conditions, with experimental units consisting of fiber glass vases containing 150 dm3 of Red Yellow Latosol, previously fertilized. Treatments consisted in cultivating cassava plants alone and associated with three weed species (Bidens pilosa, Commelina benghalensis and Brachiaria plantaginea). After cassava shooting, about 15 days after planting, the excess of weeds, sown at the time of cassava planting, was removed, leaving three or six plants m-2, according to the treatments. In the first trial, it were evaluated leaf internal CO2 concentration (Ci), leaf temperature (Tleaf) and photosynthetic rate (A), being also calculated the CO2 consumption (ΔC) of cassava plants. In the second trial, it were evaluated stomatal conductance (Gs), vapor pressure in the substomatal chamber (Ean), temperature gradient between leaf and air (ΔT), transpiration rate (E) and water use efficiency (WUE). In the third trial, it were evaluated characteristics associated with the water use (transpiratory rate, stomatal conductance, vapor pressure in the substomatal chamber, water use efficiency) and photosynthesis (leaf internal CO2 concentration, CO2 consumed during evaluation, leaves average temperature at the evaluation time and photosynthetic rate) of weeds. In the first trial, B. pilosa and B. plantaginea competed more efficiently with the cassava plants by amounts of sunlight and water, while C. benghalensis seems to affect mostly the composition of incident light on the culture. In the second trial, B. pilosa was the species that most affected the development of the cassava plants. B. plantaginea showed high efficiency in water use and high photosynthetic rate. In the third trial, B. plantaginea surpassed B. pilosa by showing lower transpiratory rates, higher water use efficiency and higher photosynthetic rate. B. pilosa, in turn, was inferior to C. benghalensis as for CO2 consumption and leaf temperature.

ASSUNTO(S)

manihot esculenta fitotecnia manihot esculenta stomatal resistance resistência estomática

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