Ageing of theSilene coeli-rosa L. shoot apex under non-inductive conditions: Changes in morphology,mitotic index,and polypeptide composition

Summary Ageing was studied in the shoot apex of the long day plant,Silene coeli-rosa by maintaining it in non-inductive short day conditions for 170 days. The dimensions, the zonation, and the polypeptidic pattern of the shoot apex, and the rate of leaf initiation were altered in 170-day-old plants compared with young plants grown under the same conditions (28 days). In aged plants, the number of cells increased in all shoot apical zones and, notably, the mitotic index increased in the axial zone; however, the rate of leaf initiation slowed down. These changes showed some similarities to those during the intermediate phase in quantitative photoperiodic species. The two-dimensional mini-gel electrophoretic study of protein extracts from shoot apices of young and ageing plants maintained in non-inductive conditions revealed 489 common polypeptidic spots, 13 unique to the young state and 24 new ones specific to aged plants. The spots characteristic for each state represented only 3.6% of the total identified polypeptides, but apical development under non-inductive conditions was characterized by qualitative changes in the polypeptide complement.Abbreviations C nuclear DNA complement - 1D gel first dimension gel - LD long day - NEPHGE non equilibrium pH gradient electrophoresis - SD short day - SDS sodium dodecyl sulfate - TCA trichloracetic acid