Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

The Researches on Some Seed Characteristics of Magnolia grandiflora L. and Magnolia x soulangiana Soul.

Morphology, maturation time, germination obstacle or dormancy physiology and seed vigor (direct or indirect) regarding the seeds of the species Magnolia grandiflora L. and Magnolia x soulangiana Soul. have been researched by a number of experimental studies carried out in laboratory.

The findings obtained revealed that the species Magnolia grandiflora L. and Magnolia x soulangiana Soul. differ in average values of seed sizes such as width, length and thickness, while there is no difference between average seed weights and 1000-seed weights. 1000-seed weight of Magnolia grandiflora L. and Magnolia x soulangiana Soul. were found to be 210.31 g and 209.01 g respectively.

Trials about maturation time of seeds showed that seeds of Magnolia grandiflora L. and Magnolia x soulangiana Soul. reach sufficient maturity in December and October respectively.

Dormancy, which requires preliminary treatment, or germination obstacle are existent in the seeds of magnolia species. During the study, cold stratification (classical stratification), naked stratification, conditioning by osmotic stress and stratification + treatment by hormone (GA3) in order to eliminate the said germination obstacle were researched experimentally for both species.

Trials results revealed that naked stratification and conditioning by osmotic stress are not sufficient to eliminate germination obstacle in the seeds of both species.

Results of germination test made on the seeds to which cold stratification was applied at 2 different temperatures, 20 ºC and 25 ºC, at 3 months, 4,5 months and 6 months periods, were analyzed in accordance with some parameters, namely germination percentage (GP%), mean germination time (MGT – day) and germination value (GV); and the findings obtained showed that there were significant differences as to the species and stratification times. The highest germination percentage in the seeds of Magnolia grandiflora L. was obtained from the seeds to which stratification was applied for a period of 4.5 months and germinated at 25 ºC (81%) and a period of 6 months and germinated at 20 ºC (81%). The highest germination performance in terms of germination parameter was obtained from the seeds to which stratification was applied for a period of 4.5 months and germinated at 25 ºC. The highest germination percentage in the seeds of Magnolia x soulangiana Soul. was obtained from the seeds to which stratification was applied for a period of 4.5 months and germinated at 25 ºC (91%) and a period of 6 months and germinated at 20 ºC (94%). The highest germination performance in terms of germination parameter was obtained from the seeds to which stratification was applied for a period of 4.5 months and germinated at 25 ºC.

Effects of the hormone applications, which were tried at 1500 ppm and 2000 ppm to the seeds of both species for the purpose of eliminating inhibition of germination, were realized in combination and with stratification times of 1.5 months and 3 months. And findings of the trial revealed that GA3 + 3-months stratification provide the highest germination parameter (85 % and 95 %) in the seeds of both Magnolia grandiflora L. and Magnolia x soulangiana Soul.

In the indirect tests made for determining seed viability within the shortest time, tetrazolium and electrical conductivity trials were carried out and it was found that tetrazolium method can reflect the vital power of the seeds sufficiently in identifying vitality.

Based on these results, it was considered that stratification + hormone (GA3) treatment is a more appropriate preliminary treatment than the other options, particularly cold stratification, as to performance criteria such as germination percentage (GP), mean germination time (MGT), germination value (GV) and time of application. And use of the said stratification + hormone treatment is suggested as the method which provides the highest performance value in eliminating dormancy or inhibition of germination in the seeds of both Magnolia grandiflora L. and Magnolia x soulangiana Soul.