Physiological aspects of coffee growth and production / Aspectos fisiológicos do crescimento e da produção do cafeeiro

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

In this work, changes in vegetative growth, crop production, branch die-back, gas exchange, carbohydrate metabolism, nitrogen and pigment concentration were investigated in leaves and branch segments in coffee trees grown (north-south orientation) under field conditions along two years. Samplings and measurements were conducted using outer leaves from the upper and lower strata from east- and west-faced sides of a coffee hedgerow in branches of three classes of leaf-to-fruit ratio (0 to 6; 6.1 to 14; >14 cm2 fruit-1) in 2006-2007 and leaf-to-fruit ratio >20 cm2 fruit-1 in 2007-2008. Growth evaluations were accomplished from November 2006 to March of 2007 and from November 2007 to May 2008. Evaluations of gas exchange, carbon metabolism, nitrogen and pigment concentration were accomplished in March 2007 and March 2008, while crop yield was evaluated in April 2007 and May 2008, and branch die-back in July 2007 and July 2008. Branch growth rate was larger, whereas production and branch die-back were smaller with increasing leaf-to-fruit ratio regardless of canopy positions in 2006-2007. In 2007-2008, branch growth rate was larger in the upper strata in comparison with the lower strata in both east and west positions of the hedgerow. In 2007, total crop yield and production of welldeveloped fruits in east and west faces were both larger in upper strata than in the lower strata, while the production of partially-empty fruits was larger in upper than in lower strata in the east canopy position. Among the faces of the row, total crop yield and production of well-developed- and partially-empty-fruits, as well as branch dieback in the upper strata, all were larger in the east face than in the west one. Total crop yield was remarkably larger in 2006- 2007 than in 2007-2008 regardless of canopy position. Relationships among crop production with photosynthetic rates, carbon isotope composition and carbohydrate concentration could not be found, which could be explained by the loss of branch autonomy, particularly in periods of high demand of assimilates by the fruits. In support to these results, substantial alteration in activities of key enzymes associated with carbon metabolism was not verified. Relationships among branch die-back with availability of minerals and carbohydrates as well as with oxidative stress were also not found. In addition, variations in biennial production were not verified among the faces of the tree canopies. Possibly, larger production of the east face could be associated with larger light supply. Maintenance of gas exchange along the day could be largely associated with lower atmospheric demand than with feedback inhibition of photosynthesis. In this sense, stomata seemed strongly responsive to increasing evaporative demand; however, endogenous rhythms might also be associated with stomatal closure, especially at the end of afternoon.

ASSUNTO(S)

coffee produção ecofisiologia vegetal bienalidade café carbon metabolism metabolismo do carbono production

ACESSO AO ARTIGO

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