Ultrastructure of Nicotiana Alata Pollen, Its Germination and Early Tube Formation

Abstract

Both internal anatomy andexternal morphology ofthe mature pollen grain of Nicotiana alata have been studied, together with pollen activation and tube emergence and its cytological zonation.A peculiar feature of mature pollen is the occurrence in the vegetative cell cytoplasm of a large quantity ofstacked cisterns of rough endoplasmic reticulum, which thendissociate during pollen activation.Pollen tubeemergence generally occurs 2hr 30minafterhydration, while cytological zonation is complete 4 hr 30 min after hydration when the first callosic plug is formed.

Pollen tube tip growth

“…Callose plug formation has been described by Cresti & van Went (1976). Cresti et al (1985) also described four zones, similar to those in Lycopersicon, from the pollen tubes of Nicotiana. In Prunus pollen tubes growing in vivo a total of live cytological zones were described, though with somewhat different compositions from those of Lycopersicon (Uwate & Lin, 1980).…”

Pollen and Stigma Structure and Function: The Role of Diversity in Pollination

“…Whether tubes emerge on a dry stigma surface, from a grain submerged in stigma exudates, or from pollen germinated in vitro, the grain organizes its cytoplasm and cytoskeleton to support the extension of a single tube. These changes occur within minutes after hydration and include the formation of filamentous cytoskeletal structures that wrap around the nuclei, actin cytoskeleton polarization toward the site of tube emergence (Tiwari and Polito, 1988;Heslop-Harrison and Heslop-Harrison, 1992), reorientation of the large vegetative nucleus so that it enters the extending tube before the generative cells (Heslop-Harrison et al, 1986a;Heslop-Harrison and Heslop-Harrison, 1989;Lalanne and Twell, 2002), assembly of mitochondria and polysaccharide particles at the site of the elongating tube tip (Cresti et al, 1977(Cresti et al, , 1985Mazina et al, 2002), and selection of the pollen plasma membrane for secretory vesicle targeting and deposition of callose (b-1!3 glycan) at the site of tube emergence (Johnson and McCormick, 2001).…”

Ultrastructure and cytochemistry ofEucalyptus globulus(Myrtaceae) pollen grain

“…Extensive RER stacks, like those in Eucalyptus globulus, have been reported in the pollen of several species of the Scrophulariaceae (Jensen et al, 1974) and of many other unrelated families (e.g. Cresti et al, 1975Cresti et al, , 1985Van Aelst & Van Went, 1991;Luegmayr, 1993). These RER stacks have been correlated with the arrest of metabolic activities in the mature pollen, since during pollen activation the metabolism in the VC resumes and the stacked cisternae becomes free in the cytoplasm (Jensen et al, 1974;Cresti et al, 1975Cresti et al, , 1985Ciampolini et al, 1988).…”

“…Cresti et al, 1975Cresti et al, , 1985Van Aelst & Van Went, 1991;Luegmayr, 1993). These RER stacks have been correlated with the arrest of metabolic activities in the mature pollen, since during pollen activation the metabolism in the VC resumes and the stacked cisternae becomes free in the cytoplasm (Jensen et al, 1974;Cresti et al, 1975Cresti et al, , 1985Ciampolini et al, 1988). Similarly to the dry mature seeds (Bergfeld & Schopfer, 1984), the RER stacks in the mature pollen are likely induced by the protoplasmic dehydration, which leads to metabolic arrest.…”

“…Studies on other plants have shown that the composition and organization of the pollen grains are different among species (e.g. Jensen et al, 1974;Cresti et al, 1975Cresti et al, , 1985Cresti et al, , 1988Cresti et al, , 1990Van Aelst & Van Went, 1991;Van Aelst et al, 1993;Hess, 1995;Dinis et al, 2000). The main differences are in respect to the pollen wall architecture, the number and degree of development of the organelles, the amount and nature of reserve substances, and the generative cell (GC) composition and its association with the nucleus of the vegetative cell (VC).…”