Physiological Study of Cupuaçu [Theobroma grandiflorum (Willd. ex. Spreng.) Schum.,] Tree Progenies Subjected to Water Deficiency

Aims: The study aimed to investigate the physiological behaviour of cupuaçu tree progenies subjected to water deficiency.

Study Design: The experimental design was completely randomised, in a 2x7 factorial scheme (2 water regimes: with and without water deficiency and 7 cupuaçu tree genotypes), totalling 14 treatments with 5 replications.

Place and Duration of Study: The experiment was carried out from March to November 2016, in a greenhouse of Embrapa Eastern Amazon in the municipality of Belém, State of Pará, Brazil, located at the geographic coordinates 01º 27' of South Latitude and 48º 30' of West Longitude.

Methodology: The following parameters were evaluated: predawn water potential (Ψpd), water potential of xylem (Ψx), stomatal conductance (GS), transpiration (E), photosynthesis (PS), internal carbon concentration (CI), internal and external carbon ratio (CI/CA), chlorophyll a (Chl a), b (Chl b), total (Chl total), anthocyanin (ANT), carotenoids (CAR), instantaneous carboxylation efficiency (ICE), and water-use efficiency (WUE). The variables were submitted to multivariate analysis.

Results: Two distinct groups were resulted. Group 1 retained the treatments with water deficiency and group 2 retained the control treatments. This result occurred because the water conditions were different. The MC1 was influenced by PS because photosynthetic pigments are essential for photosynthesis. PS, GS, Chl total, Chl a, CAR, CI, CI/CA, Ψpd, Ψx, E, and ICEresulted with greater intensity in the control treatments, and with less intensity in the genotypes submitted to water deficiency.

This behaviour is because of water deficiency that reduces photosynthesis. The MC2 was influenced by Chl b, ANT, and WUE. In water deficiency, the distinction in the physiological behaviour of cupuaçu tree progenies occurs in relation to the progenies that did not undergo water stress.

Conclusion: The cupuaçu tree progenies under water restriction condition have a positive effect on water-use efficiency.