Effects of Seed Weight and Substrate on Germination and Growth of Non-toxic Jatropha curcas L. Seedings

Aims: We characterized the responses of non-toxic seedlings of Jatropha curcas L. to variation in seed weight and substrate during their germination and growth.
Study Design: Two analytical experiments using a randomized controlled trial approach were applied to consider the effects of seed weight and substrate.
Place and Duration of Study: Non-toxic seeds from the east coast of Mexico were selected during two consecutive years and their seedlings were studied during one month after emergence.
Methodology: The seeds were grouped into different weight categories (400-499 - 800-899 mg). The substrates evaluated were sandy, sugarcane compost and a mix of sandy and sugarcane compost (sandy-compost, 2:1). While sandy substrate was poor in organic matter (OM), sugarcane compost was rich in OM. Germination, survival rate and mean germination time (MGT) were evaluated by seed weight category and substrate. We measured stem length, root collar diameter, number of leaves and leaf area every week, and at the end of the experiments total dry biomass was recorded.
Results: The heaviest seeds had higher germination rates (86.3%±7.1%) compared to the lightest seeds (69.9%±12.2%) in all substrates. Survival rate was 10% lower for the lightest seeds in sandy-compost and for the heaviest seeds in compost. MGT was not significantly different between seed weight categories or substrates (P=.32). Heavier seeds produced bigger seedlings in terms of stem length, root collar diameter, number of leaves, root length, and total dry mass in sandy-compost(P<.05). However, when substrates were compared, the substrate effect was larger than the effects from seed weight, with the largest seedlings found in compost (P<.05), regardless of seed weight.
Conclusion: Seed weight improved germination rates in sandy and sandy-compost substrates. Compost increased seedling growth regardless of seed weight.