Seed germination and seedling development of Jatropha Zeyheri :an indigenous tea plant in Limpopo Province of South Africa

Abstract

Indigenous teas are receiving much attention and global interest as a result of their nutraceutical and pharmaceutical benefits. Most of these tea plants are still collected from the wild and their domestication has become a necessity as a result of the rapid growth of the tea industry and increased global demands. However, like other indigenous plants, setbacks exist in the successful seed germination of wild tea plants on account of seed parasitism, low seed viability andgermination difficulties A study was undertaken to: (a) determine the effect of pre- treatments of Jatropha zeyheri seeds grown under laboratory conditions and (b) to evaluate growth and development of J. zeyheri seedlings under controlled conditions on different growth media. In the initial objective, matured seeds sourced from the wild were subjected to five (5) pre- treatments methods namely, clipping, piercing, de-coating, cold and hot water soaking. The sixth (6) untreated dry intact seeds served as reference. Treatments were organised in a completely randomised design (CRD) with 10 replications. Treated and untreated seeds were all placed on moistened filter-papers inside petri-dishes and incubated in a growing chamber at 27°C. At 21 days, data on mean germination time (MGT), germination rate (GR), germination index (GI) and germination percentage (GP) were collected and calculated, prior to analysis of variance (ANOVA). Fisher’ Least Significant Difference test was used to separate the means at 5% level of probability. In the subsequent objective, under greenhouse conditions, six (6) treatments namely, sand, sand + loam, loam + compost, loam + Hygromix, sand + compost, sand + Hygromix were used, while sand alone served as the reference medium. The treatments were arranged in a randomised complete block design (RCBD), replicated 10 times. Seeds were de-coated first and each seed was planted in 10 cm plastic pot, filled with the various growing media-mixtures at a depth of 2 cm and irrigated to field capacity. Data collected included seedling performance parameters, namely, MGT, GR, GI and GP as well as plant parameters namely, stem diameter (SD), chlorophyll content (CC), seedling length (SL), number of shoots (NS), dry shoot mass (DSM) and dry root mass (DRM) and were subjected to ANOVA. Fisher’ Least Significant Difference test was used to separate the means at 5% level of probability. Germination occurred at the reference and seeds treated with clipping and de-coating methods. Pierced, cold and hot-water soaked seeds failed to germinate. Treatments had significant (P≤0.05) effect on MGT, GP, GI and GR, contributing 57, 55, 51 and 55% to total treatment variation (TTV) in the respective variables. When compared with the intact seeds, MGT for the clipped seeds was at 3 days, whereas in the de-coated seeds it was in 7 days. The clipped seeds achieved 11% GP and 0.29 GI at a GR of 0.05. Noticeably, the de-coated seeds achieved highest (16%) GP and 0.3 GI at a GR of 0.08 when compared to the reference seeds. Treatments had significant (P≤0.05) effect on MGT, GP and GR of J. zeyheri seedlings, whereas no significant effects were observed on GI. Treatments contributed 25, 21, 9 and 22% to TTV in the respective variables. Relative to the reference medium, MGT for the de-coated J. zeyheri seeds sown on sand + compost occurred at 2 days, whereas emergence in sand + loam occurred at 7 days. The longest MGT (26 days) was observed in sand + Hygromix growing media. Germination percentage and GR for seeds sown on sand + compost was 1% and 1.1, whereas for seeds sown on sand + loam was 2% and 3.33E-03 and in seeds sown on sand + Hygromix, it was at 4% and 4.44E-03, respectively, when compared to the reference. In terms of plant parameters, treatments had no significant (P≥0.05) effect on SD, CC, SL, NS, DSM and DRM of J. zeyheri plantlets. In conclusion, the de-coating pre- treatment proved to be a better method for improving germination in seeds of J. zeyheri tea plant and the same de-coated seeds sown on sand + Hygromix achieved better emergence and development, proving that the growing media used was suitable to provide optimum germination and seedling development