Abstract:
BACKGROUND AND AIMS:Hydration, rupture and exine opening due to the sudden and large expansion of intine are typical of taxoid-type pollen grains. A hemispheric outgrowth external to the exine was observed on Cupressus and Juniperus pollen grains before the intine swelling and exine release. However, the actual existence of this permanent or temporary structure and its precise role in pollen hydration is still being debated. The aim of this paper is to collect information on the actual presence of this peculiar outgrowth on the surface of the Cupressus pollen grain, its structure, composition and function. METHODS:Pollen grains of several Cupressus species were observed using various techniques and methodologies, under light and fluorescence microscopy, phase-contrast microscopy, confocal microscopy, scanning electron microscopy, and an environmental scanning electron microscope. Observations were also performed on other species with taxoid-type pollen grains. KEY RESULTS:A temporary structure located just above the pore was observed on Cupressus pollen grains, as well as on other taxoid-type pollens. It is hemispheric, layered, and consists of polysaccharides and proteins. The latter are confined to its inner part. Its presence seems to regulate the entrance of water into the grains at the beginning of pollen hydration. CONCLUSIONS:The presence of a temporary structure over the pore of taxoid-type pollen grains was confirmed and its structure was resolved using several stains and observation techniques. This structure plays a role in the first phases of pollen hydration.
journal_name
Ann Botjournal_title
Annals of botanyauthors
Danti R,Della Rocca G,Calamassi R,Mori B,Mariotti Lippi Mdoi
10.1093/aob/mcr144subject
Has Abstractpub_date
2011-08-01 00:00:00pages
299-306issue
2eissn
0305-7364issn
1095-8290pii
mcr144journal_volume
108pub_type
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