Germination requirements of Allanblackia parviflora seeds and early growth of seedlings

摘要

Allanblackia parviflora A. Chev, is an indigenous fruit tree species that could be used in agroforestry systems with both environmental and economic benefits. The seed oil is of prime importance as a foreign exchange earner and is being developed as a rural based enterprise in many African countries notably Ghana, Nigeria, Cameroon and Tanzania. Methods for propagation and conservation of the species are therefore of prime importance. The seeds of the species are however difficult to germinate hindering its domestication process. Allanblackia parviflora seeds were collected from seven different populations in Ghana and were subjected to four different seed germination trials at the nursery of CSIR-Forestry Research Institute of Ghana at Fumesua, Kumasi. This was followed by studying the effect of stage of seed germination on establishment after potting. Intact seeds began germination at 7 months after sowing and at 24 months, significant (P 0.001) variations were observed in the seed germination ability of 74 accessions. Mean seed germination ranged from 0 to 35%. Significant differences in seed germination percentages among populations (P 0.001) and provenances (P 0.05) were also observed. Removal of seed coat significantly (P 0.001) enhanced seed germination. Germination percentages of seeds with seed coat removed ranged from 6 to 43% while seed germination percentages for intact seeds were less or equal to 3%. Incubation of seeds with seed coat removed in polythene bags gave an added advantage. Seeds with seed coat removed and kept in polythene bags started germinating from 2 weeks and within 10 months, 75 and 68% germination were obtained for plane and black polythene bags, respectively. Removal of germinants and potting when shoot length was at least 1 cm gave significantly higher growth (P 0.001 for shoot height, P 0.05 for stem diameter, P 0.001 for number of leaves produced) compared to when only radicle had emerged. It became evident in this study that seeds should be classified as fully germinated only when shoots begin to grow.