Diversidade funcional da partição de biomassa, ganho de carbono e do uso da água em Coffea canephora, em resposta à disponibilidade hídrica

• Autor(a) principal: Silva, Paulo Eduardo de Menezes
• Data de Publicação: 2010
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/4329
• topic: Déficit hídrico; Coffea canephora; Análise multivariada; Taxas fotossintéticas; Water deficit; Coffea canephora; Multivariate analysis; Photosynthetic rat; CNPQ::CIENCIAS BIOLOGICAS::BOTANICA::FISIOLOGIA VEGETAL::ECOFISIOLOGIA VEGETAL

The functional divergence associated with biomass partitioning, carbon gain and water use was studied in 10 clones of Coffea canephora. Seedlings, raised as rooted stem cuttings, with four leaf pairs were grown under full sunlight in 24 dm3 pots. When 8 months old, the plants were submitted to varying irrigation treatments: a group of plants was watered regularly as needed (control plants); a second group was maintained at 66% field capacity for 90 days (mild water deficit). Half of the plants of each clone were then analyzed, the other half were kept at 33% field condition for more 30 days (severe water deficit). Multivariate analysis was performed in order to evaluate the functional divergence among clones and possible strategies to cope with water deficit. In general, the total biomass was dramatically decreased in droughted plants; this was accompanied by increases in the root mass ratio and decreases in the leaf biomass ratio, whereas only minor, if any, changes in the stem biomass ratio was found, although the stem density having increased significantly in most clones under drought conditions. In control plants, higher photosynthetic rates were associated with higher stomatal conductance and increased internal-to-atmospheric CO2 concentration ratio; however, gas exchange parameters and carbon isotopic composition did not correlate significantly. Regardless of water deficit, nitrogen isotopic composition did not change consistently among the treatments. In general, clones displaying higher hydraulic efficiency (lower stem density, higher root biomass ratio, transpiration rates, apparent hydraulic conductance, and more negative water potentials) showed improved carbon gain. These clones were able to keep higher net photosynthetic rates under mild water deficit at the expense of higher water use. Under severe water deficit, partial maintenance of photosynthetic rates was, to a great extent, dependent on a more favorable leaf water status associated with more conservative traits linked to water use. It should be emphasized that decreases in photosynthesis rates were accompanied by reductions in stomatal conductance under severe drought, resulting in negative correlation between photosynthesis rates and internal-to-atmospheric CO2 concentration ratio; as a result, negative correlation between gas exchange parameters and carbon isotopic composition was observed. Traits associated with water use, such as stem density, midday water potential and transpiration rate, in addition to carbon isotopic composition (under water deficit), could be useful tools for screening promising clones in response to water availability, specially because these traits are easily obtained and showed substantial amplitude among the clones.