Ultrastructural Studies of the Pollen of Subtribe Castilleiinae, Family Scrophulariaceae

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).…”

“…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.…”

“…Jensen et al, 1974;Cresti et al, 1990;Hess, 1995) the stacked cisternae may also represent a storage site of nutrient materials. In Eucalyptus globulus the lumen of the stacked cisternae was positively stained after the Thiéry test indicating the presence of abundant neutral polysaccharides and other carbohydrates (Thiéry, 1967).…”

“…Single lipid bodies encircled completely or partially by RER cisternae have been reported in the mature pollen of several species (e.g. Jensen et al, 1974;Cresti et al, 1975Cresti et al, , 1988Cresti et al, , 1990Ciampolini et al, 1988;Van Aelst & Van Went, 1991;Van Aelst et al, 1993) but the physiological role of this association is still controversial. It has been proposed that the RER cistern encircling each lipid body acts as a physical barrier preventing the aggregation and coalescence of lipid bodies (Frandsen et al, 2001;Murphy, 2001).…”

“…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).…”