**Acknowledgements**

**Term Definition**

730 Abiotic and Biotic Stress in Plants - Recent Advances and Future Perspectives

• Zoophilous, entomophilous and

anemophilous pollen

mechanisms.

exine and intine.

rehydration.

• Pollen engorgement Pollen maturation is associated with accumulation of starch granules in the

• Harmomegathy The capacity of pollen grains to change shape in response to a decrease in

• Furrow A fold region where the exine cell wall has reduced thickness, whilst intine

• Development arrest state Term used to indicate the state of physiological and metabolic arrest when

• Of the locular fluid changes Central cavity in the anther where pollen grains develop. The loculus is

grains are tightly packed. • Mechanical layer External cell layer of the anther wall where, after tapetum degeneration,

• Pollenkitt Hydrophobic glue derived from the degeneration of the tapetum,

• Pollen viability Term used to indicate the percentage of viable pollen (i.e., able to emit

for anther opening and pollen exposure

the pollinator body and to the stigma surface.

pollen grains reduce water content before dispersal.

cytoplasm. This process is called engorgement.

exposed in the anther. Secondary presentation involves developmental relocation of pollen from the anther to another floral organ. Pollen grains are not presented by the anther when they are launched using different

volume during dehydration and prior to the development arrest state. This dynamic process is controlled by the mechanical properties of the cell wall (furrows) and can be reversed by rehydration on the stigma. When pores are absent, this increase and decrease in volume is due to the elasticity of

is thicker. Furrows allow the cell wall to collapse to comply with the decrease in pollen volume during dehydration and increase volume during

filled with the locular fluid which is secreted by the tapetum and serves to nurture pollen. In cross-section, anthers show four locules. The composition of the locule fluid changes during pollen development, and before anther dehiscence the fluid is reabsorbed by the filament or other floral parts to allow pollen presentation. The locular fluid is abundant in anthers with monad and tetrad pollen, but is reduced in species with pollinia or where

cells develop lignified wall thickenings. The mechanical layer is responsible

composed of saturated and unsaturated lipids, carotenoids, flavonoids, proteins and carbohydrates. Pollenkitt makes grains stick to the anther, to

pollen tubes and fertilise). Pollen viability can be assessed by hand pollination, in vitro germination and several methods evaluating physico-

Pollen dispersal by animals, insects and wind, respectively.

Special thanks to Drs C. Carrizzo, G.G. Franchi and M. Nepi who helped with the development of some of the arguments reported in this review, Dr D. Nocentini for providing pictures shown in Figure 3 Claudia Faleri and Massimo Guarnieri for technical assistance. RD is indebted to the Australian Grains Research and Development Corporation for financial support (GRDC, grants CSP00175 and CSP00143).
