Effect of pre-sowing treatment on germination of Macadamia integrifoloia and Ziziphus mauritiana fruits

Many Kenyan farmers are integrating fruit trees into their farming systems as an insurance against the uncertainties of weather. However the hard coated fruits impose particular problem in germination because their fruit coat forms an impermeable cover that restricts water absorption (imbibition). Most tree fruits should be pre-treated to break this dormancy, enhance rapid and uniform germination of seed. The main aim of this experiment is to establish appropriate presowing methods to improve germination of hard coated fruits using Macadamia integrifolia and Ziziphus mauritiana. Fruits from each species were sampled, then divided into 4 samples of 50 fruits each and each sample was subjected to different soaking period (soaking for 24hrs, 48hrs and 72 hours). Water was replaced after every 24 hours from fruits soaked for 48 and 72 hours for both species. Each soaked sample was also dried for at least 6 hours (one day) before sowing to facilitate cracking. Results obtained of germination rates of fruit sample shown that, the fruits soaked for 72 hours had the highest germination percentage for Macadamia integrifolia then the rest. Germination rates of fruits sown with no pre-sowing treatment (control) were the lowest for both species (Macadamia integrifolia and Ziziphus mauritiana). From the results, the number of germinants shows great significance difference between the control and other 3 treatments (where fruits were soaked for 24 hours (one day), 48 hours (2days) and 72 hours (3days) for both species. The optimum germination of the hard coated fruits of Macadamia integrifolia was realized after soaking fruits in cold water for 72 hours or 3 days; while the optimum germination of fruits of Ziziphus mauritiana was realized after sowing fruits in cold water for 24 hour, thus no need to soak for more than 24 hours in case of Ziziphus mauritiana. Germination rates of hard coated fruits (e.g. Macadamia nuts) increases with duration of soaking - the longer the soaking period the higher the speed of germination. Results from this experiment are useful in making recommendations to improve propagation of hard coated fruits in general.

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