Spore Wall Development inSchizaea Pectinata(Schizaeaceae: Pteridophyta)

Abstract

A blechnoid type of spore wall developed in Scltizaeapecrinaru (L.) Sw. consisting of inner and outer exospore, inner and outer perispore. The inner exospore was initiated by the formation of electron dense lamellae from the surface of the plasma membrane around each member of the tetrad. Tetnds were enclosed within chambers in the plasmodia1 tapetum. The outer exospore constituted the bulk of the spore wall and accumulated, at first. in irregular patches on the inner exospore; its deposition involved the activity of the plasma membrane of the plasmodial tapetum. A reticulate pattern developed on the outer exospore as a result of a differential pattern of growth involving plasmodia1 tapetum activity. The heterogeneous inner perispore was firmly attached to the outer exospore and its deposition involved structures found in the sporangial loculus. The outer perispore was loosely attached to the inner perispore and its formation was associated with composite bodies, which differed from the structures involved in inner perispore development, and consisted of partially polymerised sporopollenin, phenolics and silicon particles. Only the initiation of the inner exospore involved sporal activity, the development of the other parts of the spore wall were intimately associated with the plasmodial tapetum and with bodies present in the sporangial loculus. There is a large amount of literature relating to microsporogenesis and the ontogeny of the angiosperm pollen grain but relatively little literature on spora! ontogeny of the pteridophytes in general and for the homosporous ferns in particular.The greatest contribution to early ultrastructural studies of sporogenesis within the pteridophytes was by Lugardon (1966Lugardon ( , 1968 on spore wall ontogeny and cytology in Bleclrtirriti spicnrif, Ostiiirtidn regnlis and Eqiiisetirtii itin.vitiziiiti. GullvAg ( 1970) compared events which occurred during the development of L~copodiirni oiriiotiriirtii spores with events which occurred during microsporogenesis in the angiosperms and Robert (1970, 1971 a, b) working on Selnginella krnirssinnn and S. selaginoides discussed the involvement of the tapetum in the formation of the spore wall. Lugardon (1971Lugardon ( , 1972 defined the terminology which he used in describing the various wall layers of pteridophyte spores. He was of the opinion that the sub-division of the exine, defined in terms of the organisation of this layer in pollen, could not be applied correctly to the layers of the exospore. From descriptions of spore wall structure in a wide selection of homosporous ferns (Lugardon 1974(Lugardon , 1975(Lugardon , 1976 he drew a comparison between pollen and pteridophyte'spore walls (Lugardon 1978). Lugardon's terminology has been applied to the spore wall layers in S. pecriiintn.Publications by Sheffeld & Bell (1979) on ultrastructural events during meiosis in Pferidiurn aqrriliriirm, by Lugardon (1979) on the formation of the spore wall from the tetrad stage in Psilotiitti and by Pettitt (19790) and cytochemical aspect...

Spore morphology and wall ultrastructure ofActinostachys pennula(Sw.) Hook. andA. subtrijuga(Mart.) C. Presl. (Schizaeaceae)

“…The sporoderm stratification described in the present work coincides with that described by Parkinson (1995a), who studied the spore wall development of Schizaea pectinata from South Africa. This author refers to a clear distinction between the inner and outer perispore layers, a feature that is also evident in the perispore of A. pennula and A. subtrijuga described in our contribution.…”

“…Moreover, in S. pectinata are mentioned different types of bodies that consist exclusively of perisporal material and are associated with the formation of the perispore. In addition, a combination tapetum consisting of a cellular, parietal component and a plasmodial component occur in the species (Parkinson 1995a(Parkinson , 1995b. Although the type of tapetum is unknown for Actinostachys pennula and A. subtrijuga, we suggest that the spherules with granular structure found in the spores of these species are spherical bodies that contribute to the perispore formation and remain in the spore surface as a remnant of the tapetum.…”

“…The author characterised the spores of Actinostachys as having a pattern of parallel ridges and furrows of the exospore, giving them a striate appearance. Parkinson (1994Parkinson ( , 1995aParkinson ( , 1995b, in studying the spore wall development in Schizaea pectinata from South Africa, observed the sporoderm to have a two-layered exospore and a two-layered perispore. Ramos studied with LM, SEM and transmission electron microscopy (TEM) the spores of Schizaea fistulosa Labill.…”