Physiological Traits and Metabolites of Cacao Seedlings Influenced by Potassium in Growth Medium

Yan-Mei Li, Marshall Elson, Dapeng Zhang, Richard C. Sicher, Hang Liang, Lyndel W. Meinhardt, Virupax Baligar

College of Natural Resources and Environment/College of Computer and Information Science, Southwest University, Chongqing, China.
Crop Systems and Global Change Laboratory, USDA ARS, Beltsville, USA..
Sustainable Perennial Crops Laboratory, USDA ARS, Beltsville, USA.
Sustainable Perennial Crops Laboratory, USDA ARS, Beltsville, USA;.

DOI: 10.4236/ajps.2013.45133                

Abstract

Cacao (Theobroma cacao L.) is of significant economic importance in several tropical countries but its yield potentials are low mainly because of poor soil fertility especially low levels of potassium (K). Cacao has a high demand for K to maintain healthy growth and production. Knowledge of K use in cacao will help the development of suitable crop management practices and will aid breeding varieties adapted to environments with a limited soil K supply. Using a plant growth chamber, we investigated the growth and physiological traits among three cacao varieties at three levels of growth medium K (52, 156, and 469 mg·plant^-1). Significant K effects were observed on growth traits including stem diameter, root length, chlorophyll b, and the ratio of chlorophyll a/b. Significant K effect was also found on carbohydrate metabolites, such as fructose, glucose, myo-inositol, raffinose and starch. However, no K effect was observed in other growth and physiological indicators, including biomass of seedling and net photosynthetic rate. There were significant genotype differences on seedling growth indicators, including stem diameter, stem height, total biomass, leaf biomass, leaf area, root length, chlorophyll a + b and carotenoids. Genotype difference was also found on all measured carbohydrate and starch metabolites, except maltose and raffinose. Results of this study indicate that although K plays a critical role in cacao tree growth and productivity, cacao may be less sensitive to K deficiency during the seedling stage. The present results improved our understanding about K and plants interaction in cacao seedlings, which is useful for crop management and germplasm utilization.

Keywords

Cocao; Photosynthesis; Chlorophyll; Carbohydrates; Sugars

Conflicts of Interest

The authors declare no conflicts of interest.

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