Unraveling relationships of prompt germination among four species of Inga Mill detected by morpho-anatomical and histochemical traits

Abstract

Seeds are structured with specific morphological attributes that influence their ability to establish new sporophytes in their environments. In this sense, studies of the morphological traits of seeds contribute to the understanding of processes related to the germination, storage and management of plant species. The aim of this study was to characterize the seeds of four species of Inga in terms of biometrics, morphoanatomy and histochemistry. Furthermore, the relationships between these trait variations among Inga species and their impact on seed germination were investigated. The seeds presented high moisture levels, above 40%. I. edulis had 20% viviparity, in contrast to I. cinnamomea, which had 0.1% viviparity. The seeds of I. pezizifera presented more than 50% polyembryony, which influenced seedling vigor. The tegument did not affect the germination percentage. On the other hand, the presence of the tegument influenced the mean germination time for I. cinnamomea, whose seeds with tegument germinated, on average, after 16 days, while the seeds of the other species germinated in 2 to 3 days. Morphologically, the seeds were anatropous, elliptical and exalbuminous. The embryonic axis was well developed and hairy. The tegument was membranous or leathery and caused no physical barrier to germination. However, differences were observed among species in terms of the thickness of the tegument and of the tegument cell walls. In cotyledons and on the embryonic axis, there was a wide distribution of neutral polysaccharides, starches and proteins. Lipids were scarce. Therefore, when taken together, the results concerning Inga seed characteristics contributed to elucidating the factors related to their accelerated and high rates of germination, which reflect their potential for early seedling establishment. © 2021