Morphology, relations water and photosyntheses in two cultivate of Coffea canephora submitted the of water déficit / Morfologia, relações hídricas e fotossíntese em duas cultivares de Coffea canephora submetidas ao déficit hídrico

AUTOR(ES)

Paulo Cezar Cavatte

DATA DE PUBLICAÇÃO

2007

RESUMO

In this study we aimed to expand our earlier understanding on the mechanisms associated with drought tolerance within Coffea canephora. Two cultivars of C. canephora, robusta (drought-sensitive) and kouillou (drought-tolerant) were grown in 24-L pots until 12-month old, when an irrigation and a drought treatment were applied. Plants were droughted until predawn water potential ( Ψpd) reached 3.5 MPa, when they were re-watered. Physiological variables were evaluated over the course of drying whereas morphological traits were assessed at the end of the experiment. Under control conditions, robusta showed less dense crowns with larger leaf area (60%), larger biomass accumulation (45%), and larger leaf area to root surface ratio (21%) than kouillou. Internal water stress developed faster in robusta than in kouillou after withholding irrigation. Kouillou, but not robusta, was able to adjust osmotically, although both cultivars showed decreased tissue elasticity (chiefly in kouillou) under drought. Under control conditions, apparent hydraulic conductance KL, long- term transpiration rate (E), rate of net carbon assimilation (A), stomatal conductance (gs) and mesophyll conductance (gm) all were larger in robusta than in kouillou. During the course of drying, decreases in A, gs and gm were stronger in the former. However, the larger stomatal sensitivity to decreasing Ψpd in robusta was not translated into larger decreases in E. Regardless of cultivars and treatments, changes in gm paralleled those of gs. Treatments affected only slightly some of the chlorophyll a fluorescence parameters. Cellular damages were more pronounced in droughted plants of robusta than in those of kouillou. Leaf area was halved, but only in stressed plants of robusta. The lower drought tolerance of robusta in comparison to kouillou was associated with higher absolute values of gs, E and KL, shallower root system and larger shoot-to-root ratio, larger vulnerability towards cavitation and cellular damages for a given water potential.

ASSUNTO(S)

irrigação coffee irrigation fisiologia vegetal gas exchanges arquitetura da copa trocas gasosas potencial hídrico crowns architecture water potential café

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