Abstract
Seed morphology underpins many critical biological and ecological processes, such as seed dormancy and germination, dispersal, and persistence. It is also a valuable taxonomic trait that can provide information about plant evolution and adaptations to different ecological niches. This study characterised and compared various seed morphological traits, i.e., seed and pod shape, seed colour and size, embryo size, and air volume for six orchid species; and explored whether taxonomy, biogeographical origin, or growth habit are important determinants of seed morphology. We investigated this on two tropical epiphytic orchid species from Indonesia (Dendrobium strebloceras and D. lineale), and four temperate species from New Zealand, terrestrial Gastrodia cunnninghamii, Pterostylis banksii and Thelymitra nervosa, and epiphytic D. cunninghamii. Our results show some similarities among related species in their pod shape and colour, and seed colouration. All the species studied have scobiform or fusiform seeds and prolate-spheroid embryos. Specifically, D. strebloceras, G. cunninghamii, and P. banksii have an elongated seed shape, while T. nervosa has truncated seeds. Interestingly, we observed high variability in the micro-morphological seed characteristics of these orchid species, unrelated to their taxonomy, biogeographical origin, or growth habit, suggesting different ecological adaptations possibly reflecting their modes of dispersal.
Highlights
Most orchid species are endangered because of over collection and loss of habitat, so there is an urgent need to develop techniques to conserve them both in situ as well as ex situ [1]
Seeds in the Dendrobium species were generally yellow with slight differences in intensity; the remaining genera produced brown seeds that varied in tone intensity, from light to dark brown
During seed morphology assessment, we found that seeds of
Summary
Most orchid species are endangered because of over collection and loss of habitat, so there is an urgent need to develop techniques to conserve them both in situ as well as ex situ [1]. Seed morphology can provide relevant information about orchid evolution and adaptations. This information could be useful in comparative studies, since seed characters are Plants 2020, 9, 161; doi:10.3390/plants9020161 www.mdpi.com/journal/plants. Previous studies have used seed morphology to investigate taxonomic, phylogenetic, and phytogeographic relationships among orchid species [6,9,10,11,12,13,14]
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