The ovule and anther development of Helichrystun rupestre var. errerae from Pantelleria is studied. The ovule is anatropous, tenuinucellate, uni- tegmic, endotheliate and is derived from a two-zonate primordium. The archespore is one- or two-celled and all the megaspores show a functional tendency, although only the chalazal one is able to form the gametophyte according to the Polygonum type. The polar nuclei fuse before fertilization and the three antipodal cells divide further. Anthers are tetrasporangiate and their wall development conforms to the Dicotyledonous type. The epidermis persists at maturity and the endothecial cells thicken their walls. The tapetum is of the periplasmodial type and its cells become pluri- nucleate during microsporogenesis. The number of microsporocytes varies along ‘the length of the same locule. Arrangement of the resulting microspores is tetra hedral, isobilateral or decussate. Pollen grains are three-celled when shed. Degenerating microsporocytes and microspores have frequently been found. © 1987 Taylor & Francis Group, LLC.
Embryological observations on heliclirysum rupestre (Rafin.) dc. var. errerae (tineo) pignatti
FUGGI, Amodio;
1987
Abstract
The ovule and anther development of Helichrystun rupestre var. errerae from Pantelleria is studied. The ovule is anatropous, tenuinucellate, uni- tegmic, endotheliate and is derived from a two-zonate primordium. The archespore is one- or two-celled and all the megaspores show a functional tendency, although only the chalazal one is able to form the gametophyte according to the Polygonum type. The polar nuclei fuse before fertilization and the three antipodal cells divide further. Anthers are tetrasporangiate and their wall development conforms to the Dicotyledonous type. The epidermis persists at maturity and the endothecial cells thicken their walls. The tapetum is of the periplasmodial type and its cells become pluri- nucleate during microsporogenesis. The number of microsporocytes varies along ‘the length of the same locule. Arrangement of the resulting microspores is tetra hedral, isobilateral or decussate. Pollen grains are three-celled when shed. Degenerating microsporocytes and microspores have frequently been found. © 1987 Taylor & Francis Group, LLC.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
