MORPHOANATOMICAL RESPONSES OF CLONAL COCOA GENOTYPES TO SOIL FLOODING

Abstract

The effects of soil flooding on the anatomy of seven T. cacao clones (CP-49, CCN-10, PH-16, CP-06, CEPEC-2007, CEPEC-2008 and PS-1319), obtained by rooting medium of stem cuttings, aiming to elucidate the possible mechanisms of tolerance to anoxia, to subsidize the cultivation of these clones in hydromorphic soils or with drainage problems. The experiment was carried out under greenhouse conditions at UESC, Ilhéus, BA. The plants were submitted to two water regimes (with and without flooding) for a period of 45 days. The formation of lenticels at the base of the stem, at eight days of flooding, was a striking feature in the survival process of clonal genotypes. The clones from the flooded treatment showed more starch in relation to the control treatment. There was an enlargement of the intercellular spaces in the different organs of most of the plants of the evaluated clonal genotypes. Aerenchyma formation was noted in clones CP-49, CCN-10, PH-16, CP-06 and PS-1319. The non-flooded CP-49 clone presented a higher amount of phenolic compounds, while in the other clonal genotypes these compounds were present in greater amounts in the flooded treatment. The development of a greater amount of adventitious roots in the plants of clones CP-49 and CCN-10 demonstrated greater morphoanatomical plasticity of these clones in relation to the others, which had these alterations less pronounced and were more sensitive to substrate flooding. The plants of the clonal genotypes CEPEC-2008 and PS-1319 showed lower foliar plasticity in response to soil flooding, in relation to the other clones evaluated. Clones CCN-10 and CP-49 were the most tolerant to soil flooding, while clones CP-06 and CEPEC-2007 were considered moderately tolerant and clones CEPEC-2008 and PS-1319 were considered non-tolerant. Therefore, clones CCN-10 and CP-49 have the potential to be cultivated in hydromorphic soils or with drainage problems.