Análise de crescimento de dez cacaueiros híbridos

The development of 10 cacao hybrids was studied under greenhouse conditions. The objective was to determine differences in physiological parameters through a comparative growth analysis. The plants were harvested at 15 day intervals after emergence during 8 and a half months, separated into parts (root, stem and leaves) and oven dried at 75 grade centigrade to constant weight. The results indicated that there were differences in total dry matter production rate (Ct) and in leaf area (Af). The hybrids Pa 150 x ICS 1, SIC 864 x UF 613 and Pa 150 x Ma 15 had the highest Ct values and SIC 2 x ICS 1, SIC 5 x ICS 1 and SIC 5 x UF 613 the lowest ones. Throughout the experimental period, Af was the most important factor determining Ct. There were not detected significant variations in relative growth rate (Rw) among the hybrids, therefore, no changes in net assimilation rate (EA) nor leaf area ratio (FA) were found. Although, FA values were similar among hybrids, the cross SIC 22 x UF 613 showed higher FA values during the 45 days of growth. The hybrid P 12 x Ma 15 had greater FA during most of the experimental period. After the 60th day of crop growth the relative leaf growth rate (RA) and EA were constant. The mean values found for EA and RA were 0.7 g.m. exponent -2 day exponent -1 and 0.02 cm2.cm exponent -2.day exponent -1, respectively. The low values obtained for these parameters may have been caused by low irradiance. However, leaf weight ratio (Fw) was not significantly influenced by the low radiation because the decrease in leaf dry weight was similar to the decrease in total plant dry weight. After the 60th day of emergence, specific leaf area (SA) was similar among hybrids (3.0 dm exponent 2.g exponent -1). However, P 12 x Ma 15 had higher SA values than the other hybrids. Probably, the low irradiance favored the increase in Af and the decrease in total leaf dry weight of this cross. The parameters FA and Fw of the hybrids studied showed tendency to decrease with plant ontogeny.

Bibliographic Details

Main Authors:	41619 Almeida, A.A.F. de, 127058 Valle, R.R.
Format:	biblioteca
Published:	Abr-
Subjects:	THEOBROMA CACAO, HIBRIDOS, ETAPAS DE DESARROLLO DE LA PLANTA, TASA DE CRECIMIENTO, BRASIL,
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