Seed Storage Behaviour of Spondias pinnata (L. f.) Kurz; Phytohormonal and Sugar Dynamics During Embryo Development, Desiccation, and Germination

Categorisation of seeds based on their response to dehydration on natural desiccation is very important in developing effective propagation and conservation protocols for the plants. Spondias pinnata (L. f.) Kurz is an underutilised fruit tree species, reported to have a very low natural germination percentage. The present investigation was carried out as an effort to explain the least explored seed storage behaviour of S. pinnata through dynamics in embryo moisture content and endogenous phytohormones and sugars at different stages of seed development, desiccation, and germination. The phytohormone and sugar profiling were done using LC-MS/MS. A gradual reduction in the embryo moisture content was observed during seed development reaching to 22.75% at the time of seed shed, which was then drastically declined during desiccation falling below 10% and was maintained till germination, where it escalated to nearly 75%. The phytohormonal analysis showed that, freshly fallen S. pinnata seeds lack an ABA-GA balance (concentration of GA not high enough to overpower the effect of ABA) to promote germination which was found to attain only after a period of at least six months of natural desiccation. The sugar profile revealed a prominent accumulation before the seed shed that denotes successful reserve food acquisition to help with the desiccation tolerance. The elevated ABA level supported by the accretion of soluble glass-forming sucrose during seed shed with complete bypass of maturation drying thus suggest an intermediate behaviour of seed physiology for Spondias pinnata.