Morphoanatomical Adaptations to Environmental Conditions in Seeds of Some Species of the Genus Iris L. (Iridaceae, Asparagales) Growing in the Saratov Region

Abstract

Morphoanatomical features important for plant adaptation to ecological conditions have been described for seeds of seven Iris species growing in the Saratov region. Such features are the most indicative for seeds of two species, I. halophila Pall. and I. pseudacorus L. The strategy of I. halophila seeds represents development of adaptations intended to protect seed contents against penetration of saline solutions. These adaptations include the presence of a waterproof and salt-proof coating film protecting seed contents against saline solutions, the maximum level of a seed cover lignification as compared with the seeds of other species studied, and a smooth ultrasculpture of a seed cover preventing salt deposition on its surface. The strategy of I. pseudacorus seeds includes formation of seeds capable of surviving in an aquatic environment for a long time without any loss of viability. The corresponding adaptations are the following: a flattened discoid form of seeds facilitating their floating in water; the maximum thickness of a seed cover compared to other species studied; weak lignification of the seed cover, especially mesotesta; and the presence of an air cavity in the chalazal part of a seed, which reduces its specific gravity and presumably provides an embryo with oxygen when seeds float in water. Seeds of five other iris species (I. aphylla L., I. pineticola Klokov, I. pumila L., I. sibirica L., and I. tenuifolia Pall.) have identical adaptations to moderate conditions of a terrestrial environment.