Decreased Membrane Integrity in Aging Typha latifolia L.Pollen (Accumulation of Lysolipids and Free Fatty Acids)

Abstract

Aging of cattail (Typha latifolia 1.) pollen was studied at 24°C under conditions of 40 and 75% relative humidity (RH). The decline of viability coincides with increased leakage at imbibition; both processes develop much faster at the higher humidity condition. During aging phospholipids are deesterified and free fatty acids (FFAs) and lysophospholipids (LPLs) accumulate, again, much more rapidly at 75% RH than at 40% RH. The fatty acid composition of the remaining phospholipids hardly changes during aging, which suggests limited involvement of lipid peroxidation in the degradation process. Tests with phospholipase A2 revealed that the saturated fatty acids occur at the sn-1 position of the glycerol backbone of the phospholipids. The fatty acid composition of the LPLs is similar to that of the phospholipids from which they were formed, indicating that the deesterification occurs at random. This favors involvement of free radicals instead of phospholipases i n the deesterification process. Liposome studies were carried out to characterize components i n the lipid fraction that might account for the leakage associated with aging. Entrapped carboxyfluorescein leaked much more from liposomes when they were partly made up from total lipids from aged pollen than from nonaged pollen.The components causing the leakage were found i n both the polar and the neutral lipid fractions. Further purification and subsequent interchanging of the FFAs and LPLs between extracts from aged and nonaged pollen revealed that in neutral lipid extracts the FFAs are entirely responsible for the leakage, whereas i n the phospholipid fraction the LPLs are largely responsible for the leakage. The leakage from the liposomes i s not caused by fusion. We suggest that the observed loss of viability and increased leakage during aging are due to the nonenzymic accumulation of FFAs and LPLs in the pollen membranes.

Molecular mobility in the cytoplasm: An approach to describe and predict lifespan of dry germplasm

“…However, to our knowledge, this is the first experimental evidence that cytoplasmic molecular mobility in germplasm, measured by ST-EPR, is directly associated with aging rate. Despite the often-reported damage on membranes that seems to be associated with the aging of seeds and pollen (34)(35)(36), the determining factor in aging appears to be associated with the molecular mobility in the cytoplasmic surroundings. Alternatively, the viscous cytoplasm might be responsible for restricting motion of membrane components, thereby slowing down deleterious reactions taking place in membranes (37).…”

Antisense suppression of phospholipase D alpha retards abscisic acid- and ethylene-promoted senescence of postharvest Arabidopsis leaves.

“…On the one hand, hydrolysis of phospholipids need not be enzymatic because deesterification of phospholipids could be mediated by free radicals (Niehaus, 1978;McKersie et al, 1988;Van Bilsen and Hoekstra, 1993). Similarly, lipid hydrolysis may not be essential for oxidative damage because membrane lipids are susceptible to nonenzymatic peroxidation.…”

Influence of Water Content and Temperature on Molecular Mobility and Intracellular Glasses in Seeds and Pollen

“…Deterioration of seeds and pollen during storage involves many physical and chemical changes, such as disrupted intracellular integrity, decreased activities of enzymes, lipid peroxidation and deesterification, and Maillard reactions (Priestley, 1986;Wilson and McDonald, 1986;Wettlaufer and Leopold, 1991;Van Bilsen and Hoekstra, 1993;Van Bilsen et al, 1994). Since the formation of glasses in dehydrating biological tissues has been established, this physical phenomenon has been put forward as a prominent factor in the control of deterioration rates during storage (Burke, 1986;Williams and Leopold, 1989;Leopold et al, 1994;Leprince and Walters-Vertucci, 1995;Buitink et al, 1996).…”