FERTILITY OF ZEA-MAYS POLLEN DURING DEHYDRATION - PHYSIOLOGICAL STEPSOUTLINED BY NUCLEOTIDE MEASUREMENTS

A study of the modifications of maize pollen quality during dehydratio n has been realized using biochemical and physiological tests. We have measured nucleotide (ATP, ADP, ATP/ADP) and water contents in a popul ation in parallel with the in vitro germination score and seed set in the field. At anthesis, the maize pollen water content was equal to 57 +/- 2%. At this point, the ATP/ADP ratio and the in vitro germination score were below their maximum values which were reached during the f irst step of dehydration (57 to 45% H2O). When water content decreased from 45 to 20%, major changes occurred for all parameters investigate d. The in vitro germination score, seed set, ATP content, and ATP/ADP ratio decreased while ADP content increased significantly. A significa nt increase in seed set and decrease in ADP levels were observed as wa ter content decreased from 20 to 10% water content. This suggests that a modification of pollen metabolism occurred at this low hydration va lue. During the whole dehydration process, we have observed that seed set was closely correlated with ATP and ADP evolutions, contrarely to the classical in vitro germination test, and we propose to use these n ucleotide measurements as a rapid and reliable viability test.