Germination Promotion of Pinus Roxburghii, P. Halepensis and P. Wallichiana Seeds by Stratification and Chemical Treatment

Abstract

Due to low regeneration of pines, three species of pines common to our forests viz. Pinus halepensis ( Quetta Pine), P. roxburghii (Chir Pine) and P. walichiana ( bayar pine) were selected for germination and developmental studies. Our main objective was to find out methods for the improvement of germination percentage and rate of germination of the seeds of these species. Chir, beyar and Quetta pine seeds were grown under different conditions. Seeds from young trees exhibited higher germination percentage compared to those collected from over mature trees. Origin of seeds was an important factor in determining germination time and percentage. Seeds of Chir Pine collected from Dadar (Mansehra District) exhibited a higher percentage of germination (90%) as compared to other localities (e.g. Kashmir, chitral, Dir, and swat.). Pre-soaking of Chir pines seeds for 24 hours slightly increased the germination percentage, but prolonged soaking inhibited this phenomenon. Furthermore, both radicle and hypocotyl length deceased as compared to the control. Similarly in the case of beyar, pre-soaking adversely inhibited germination percentage, radical and hypocotyl length. Due to shortage of seeds, such studies could not be conducted with Quetta pine. Effects of temperature on germination percentage of Chir, beyar and Quetta pine were also studied. Optimum temperature for seed germination was about 20°C for chir and 25 for beyar and Quetta pines. Cold treatment (vernalization or stratification) enhanced both the rate and percentage of germination. Chir pine seeds exhibited 33% and Quetta pine 60% germination after a cold treatment for 35 days. Applications of chemical alone had no beneficial effects on germination, but when supplemented with stratification, both the rate and percent germination improved. Gibberellic acid and a cutokinin, 6 furfurylamino purine, at 10 and 1 mg/l respectively were better chemicals for stratification as compared to potassium nitrate and thiourea. In most cases the higher concentrations of these chemicals retarded the germination process. Application of various fertilizers to seedlings of pine species had beneficial effects on different developmental phenomenon. However, the response of an individual species was different to the same fertilizers under different growth conditions. Ammonium hypohosphate, followed by nitrophos, enhanced chir pine growth significantly as compared to control and those supplied with other fertilizers when grown under full sunlight. Contrarily, best growth was observed by ammonium nitrate application under shady conditions. Similarly, the growth of beyar pine was enhanced by ammonium nitrate under shady conditions. All these fertilizers were applied only once during the two year investigation period. Urea and ammonium sulphate were inaffective in enhancing growth in elongation. However, branch formation was enhanced by urea application both under shady and full sunlight. Applications of gibberellic acid at various concentrations was beneficial for chir pine growth. However, at 30ppm GA3 exerted maximum effect as the controls and other concentrations under both the growth in height, it induced maximum branch formation. Dormancy (an arrest in metabolic activity of plants under unfavorable conditions) is thought to be correlated with endogenous growth promoter-inhibitor balance. Therefore, systematic studies were undertaken to extract growth substances at various stages. Paper and thin layer chromatography was employed for this purpose. A predominant amount of an inhibitor was found in the dormant seeds of all the pine species. Even seeds cold treated for 15 days contained a higher level of the inhibitory and an significant amount of the promoting substance. With progression in the vernalization period, there was a concurrent decrease in the inhibitory and an increase in the growth/substances. Germinating seeds contained the highest level of the promoting and neghligible of the inhibiting moreover neghligible changes were observed in the level of regulatory substances/in warm stratified seeds of all the species as compared to the non-vernallized controls. Four growth promoting and one inhibiting substances was found to be correlated with dormancy and vernalization. These substances were found to be auxin-, gibberellin-like and restricted to ABA R respectively. It was observed that chir pine seedling were attacked by a fungus, Pythium spp. Causing damping off. This was controlled by sterilizing the soil and application of captan as suggested by Dr. Shaukat. Similarly, seeds of beyar were also attacked of not properly stored. All the project objectives could not be achieved by an early termination. The time allowed only the detailed study of chir and beyar pines, while the important Quetta pine was omitted. An extension in the project duration would have allowed detailed study regarding germination and seedling development. It is imperative that fertilization be applied in a mixture, therefore, this aspects require further study to find out suitable concentration of various fertilizers. Correlation of stratification, chemical treatment and fertilizers needs exploration for rapid seedling growth of the pine under study and other softwood flora of Pakistan. During the course of the project it was found that germination of pine seeds could be improved by cold and chemical treatments. The growth of otherwise slow growing pine species can, therefore be improved by putting into practice the project findings. Dormancy was also found to be correlated with higher indogenous inhibitor concentration and absence of growth promoting substances. Failure of pine forests regeneration in nature could be due to the “damping off” disease caused by Puthium.