Imbibition and Germination of Seeds with Economic and Ecological Interest: Physical and Biochemical Factors Involved

In this study, we describe the seed imbibition of 14 different species, from crop, forest, and native species potentially able to recover landscapes and form sustainable green cities. Seed imbibition is a fundamental physical and physiological process for reactivating metabolism and hydrolytic enzymes that will provide seed germination. We verified that the water imbibition is more closely governed by differences between osmotic potential (Ψ w ) and surrounding media than seed weight or seed hardness. In turn, seeds of Spondias tuberosa and Euterpe oleracea that have a Ψ w of −75 MPa and a tegument as hard as 200 N imbibed an insignificant volume of water. Consequently, their metabolism is not significantly affected comparing the non-imbibed seeds and 120-h-imbibed seeds. Malpighia glabra or Annona squamosa also show very negative Ψ w where the seed coat hardness is less evident; however, in these species, the seed imbibition increased the respiration rate by eight- to ten-fold in 120 h-imbibed-seeds than non-imbibed-seeds. The high-water absorption in M. glabra (49%) seems to be due to its highly convoluted tissue in the dry state, while in J. curcas and A. squamosa the presence of a highly porous seed coat must have favored seed imbibition and prompt metabolic reactivation.