title: Viability of Cururbita pepo pollen: biophysical and structural data.
abstract: During ageing of the short-lived pollen grains of Cucurbita pepo L., water loss was examined in relation to viability using biophysical ((1)H-nuclear magnetic resonance, NMR) and cytological methods (fluorochromatic reaction test, freezefracture and scanning electron microscopy). A semi-logarithmic representation of the pollen weight loss demonstrated the complexity of the dehydration process. A the study of proton loss using (1)H-NMR indicated that two major releases water of had taken place, each with different flux rates. Pulse (1)H-NMR experiments showed the occurrene of non-exponential signal decay as a function of time, indicating the existence of different fractions of water in a pollen grain sample. These fractions leave the pollen grain at different times during pollen dehydration, and one of them (that of the so-called "vital water") can be related to pollen viability. The quantity of protons giving a signal during pulse (1)H-NMR experiments was very low when the pollen grains were judged to be dead according to the fluorochromatic test. Freeze-fracture replicas of these dead pollen grains (less than 25% water content) showed that the plasma membrane had become detached from the intine surface; this ultrastructural feature might therefore be involved in the loss of pollen viability.
authors.affiliation: Laboratoire Reconnaissance Cellulaire et Amelioration des Plantes, LA INRA 879, Université Claude Bernard Lyon I, Bât. 741, 43 Boulevard du 11 Novembre 1918, F-69622, Villeurbanne Cédex, France.
authors.forename: C
authors.initials: C
authors.lastname: Digonnet-Kerhoas
authors.forename: G
authors.initials: G
authors.lastname: Gay
authors.forename: J C
authors.initials: JC
authors.lastname: Duplan
authors.forename: C
authors.initials: C
authors.lastname: Dumas