Studies Of Desiccation Tolerance In Peanut (Arachis Hypogaea.L) Seeds.

In this thesis, we studied the acquisition and induction of desiccation tolerance in developing peanut (Arachis hypogaea L. cv. Yueyou 116) seeds, examined the accumulation patterns of heat—stable proteins and soluble carbohydrates of peanut axes in relation to the development of desiccation tolerance during embryogenesis. Water status, vitrification, membrane leakage and membrane phase behavior of peanut seeds were also investigated.The results showed that the excised embryos of peanut were capable of precocious germination as early as 30 DAP,but acquired the full capacity of emergence at50 DAP. desiccation tolerance of embryos was not achieved until 45 DAP, after which desiccation tolerance was progressively gained during development even after maturation drying has begun. It was concluded that maturation drying enhanced the ability of 65 DAP embryos to withstand fast drying. Desiccation tolerance of seeds was decreased greatly after 24 hours of imbibition, and lost at all in 48 hours of imbibition. We concluded that the acquisition of desiccation tolerance of peanut embryos was a gradual event, rather than an abrupt transition. The results showed that the expression of desiccation tolerance was dependent on drying rates, desiccation tol-erance was prematurly induced when excised embryos of 25 — 35 DAP seeds (intol-erant) were dried slowly. We also found that the acquisition of desiccation tolerance of peanut axes preceded that of the embryos(de—coated seed.), the different embryonic tissues did not acquire their tolerance of desiccation synchronously.Desiccation imposed on developing immature and imbibiting peanut seed elicited an irreversible leakage of membrane. Electrolyte leakage of rghydrated axes, which prior to drying to a uniform water content h=0.1g H₂O·g^-1DW , showed a lineardecline from 25 to 65 DAP. The extent of cytoplasmic leakage is closely correlated...