Photosynthetic activity of cassava plants under weed competition

Abstract

The objective of this work was to evaluate characteristics associated with the photosynthetic activity of cassava plants under weed competition. The trial was carried out under field conditions, and experimental units consisted of 150 dm³ fiberglass boxes containing red yellow Latosol, previously corrected and fertilized. Treatments consisted in the cultivation of cassava plants which were free of weed competition and associated with three weed species: Bidens pilosa, Commelina benghalensis or Brachiaria plantaginea. After manioc sprouting started, 15 days after being planted, weeds that had been sown when manioc was planted were thinned, there were then eight plants left per experimental unit in accordance with specified treatments: cassava free of competition, cassava competing with B. pilosa, cassava competing with C. benghalensis and cassava competing with B. plantaginea. Sixty days after crop emergence leaf internal CO2 concentration (Ci), leaf temperature at the time of evaluation (Tleaf) and photosynthetic rate (A) were evaluated, also the CO2 consumption rate (ΔC) of cassava plants was calculated. A correlation matrix between variables was also obtained. All characteristics associated with photosynthesis in cassava plants were influenced by weed species. Cassava was more affected by B. pilosa and B. plantaginea in which concerns its exposition to solar radiation and water, while C. benghalensis seems to mostly affect the composition of incident light on the culture, allowing cassava to anticipate imposition when competing, even before it reaches harmful levels.

Phytosociology in agricultural areas submitted to distinct wintercropping management

“…Recently in a concept-breaking study, Aspiazú et al (2010) proved that cassava (Manihot esculenta) plants increased their growth rate, presented a higher photosynthesis rate, and consumed more CO 2 when grown under competitive circumstances with small densities of C. benghalensis (a slow growth, poorly competitive weed species) than when grown free of competition. In the same study, Brachiaria plantaginea and B. pilosa were highly harmful to cassava plants.…”

Physiology of Crops and Weeds Under Biotic and Abiotic Stresses

“…Usually, cassava producers believe that this crop is rustic and there is no need to worry too much about weed control (Albuquerque, 2008). However, the competition between weeds and cassava can affect its production in quantitative and qualitative ways (Aspiazú et al, 2010a(Aspiazú et al, , 2010b. This competition alters the efficiency of use of environmental resources such as water, light, nutrients and space among species that occupy the same ecological niche (Melo et al, 2006;Floss, 2008).…”

“…This competition alters the efficiency of use of environmental resources such as water, light, nutrients and space among species that occupy the same ecological niche (Melo et al, 2006;Floss, 2008). Aspiazú et al (2010b) studied the physiological interactions of cassava with three weed species in order to determine the mechanism the crop plants used to overcome the stress imposed by weed competition. One cassava plant was submitted to competition with one of these weed species: Bidens pilosa (three plants m -2 ), Brachiaria plantaginea (six plants m -2 ) or Commelina benghalensis (three plants m -2 ).…”

“…Based on these studies, it was proposed that the Far Red radiation, which is reflected by adjacent leaves, is a means of early detection that signals the imminence of competition during canopy development (Ballaré et al, 1990;Merotto Jr. et al, 2009;Aspiazú et al, 2010b). In addition, some species are capable of recognizing others by the amount of radiation reflected in each wave lengthessentially, the composition of the light reflected (Larcher, 2004;Aspiazú et al, 2010b Table 3. Parameters associated to the photosynthesis of cassava plants 60 days after emergence, as a function of the weed species with whom cassava plants were under competition.…”

“…Means followed by the same letter at the column, are not different by the DMRT test at 5% probability. Source: Aspiazú et al (2010b).…”