Presentation on theme: "Testing of Endogenous Germination Periodicity in Picea glauca, Pinus contorta and Pinus banksiana Seeds Ben S.P. Wang Petawawa Research Forest Canadian."— Presentation transcript:
Testing of Endogenous Germination Periodicity in Picea glauca, Pinus contorta and Pinus banksiana Seeds Ben S.P. Wang Petawawa Research Forest Canadian Forest Service, Natural Resources Canada Chalk River, Ontario, Canada K0J 1J0
Endogenous control of germination periodicity or rhythm in seeds of various species has been reported since 1920. Alnus glutinosa (Enescu 1960) Larix decidua (Rehackova 1954) Larix sibirica (Barnett and Mamonov 1989) Picea abies (Barnett and Mamonov 1989) Picea glauca (Radvanyi 1980) Picea rubens (Baldwin 1935) Pinus sylvestris (Schmidt 1929, 1930; Rehackova 1954; Barnett and Mamonov 1989) Pinus pinaster (David 1951, Gellini 1969)
Seasonal Periodicity of germination in Pinus silvestris seed of different races from Sweden to Turkey (germinative energy after 4 - and 7- days) (after Schmidt 1930, cited by Baldwin 1942).
Germination variation in Picea glauca seeds during 5-year cold storage (after Radvanyi 1980)
Longleaf pine and slash pine germination values over a 2 yr period The most obvious trends were decreases in speed of Germination in late summer or early fall and increases In the spring – usually April or May. Figure3A
Endogenous Germination Periodicity or Rhythm The inbred habit of seeds to germinate at a certain season or after a certain lapse of time following maturity is frequently retained as an inherent tendency in the germ plasm and is quite independent of external influences. (Baldwin 1942).
A Rapidly increased germination in each spring (Baldwin 1942) Seasonal variation in germinative energy of Picea rubra (P. rubens) (after Baldwin 1935, cited by Baldwin 1942) An inherited characteristic of different species and Seems to be regulated in the embryo; probably related to post-harvest dormancy (Maguire 1969).
Objective To test the hypothesis in two tree species (Picea glauca and Pinus contorta) with dormant seeds and one species (Pinus banksiana) with non-dormant seeds. It is important to test the hypothesis as it will have far reaching effects on seed testing and field sowing if it were true.
Materials and Methods (Table 1) shows the species, seed source, physical and physiological characteristics of the seeds. Table 1
All cones were collected, processed and stored according to established procedures of former PNFI. All seeds were x-rayed by replication before and after the germination test. Germination tests were made monthly from April 1980 to March 1981.
Moist chilling pre-treatment was done on top of blotter paper with a layer of Kimpak underneath in plastic germination boxes and stored at 2-4°C in the dark for 21 days. Germination tests were carried out by moving the moist chilled seeds from cold room to Conviron G30 germinators at 20°/30°C night/day temperatures with an 8- or 16- hour photoperiod.
Total germination was evaluated by the vigor class 1 - 4 (Wang 1973) and based on filled seed percentages. The rate of germination was calculated as the number of days required to reach 90% of the total germination (i.e. the less number of days, the higher the seed vigor). Cutting tests were performed on ungerminated seeds. National Tree Seed Centre Petawawa National Forestry Institute Canadian Forest Service Chalk River, Ontario. LABORATORY GERMINATION VIGOUR CLASSES FOR CONIFEROUS SEEDS HIGH VIGOURLOW VIGOUR 1. Seed coat Completely Shed. 2. Seed coat Almost shed. 3. Seed coat Slightly shed 4. Hypocotyl Raised but Cotyledons not yet visible 5. Hypocotyl raised but height shorter than that in Class #4. 6. Radical emerged but little hypocotyl visible. ABNORMALGERMINATION Cotyledons UNUSUAL GERMINATION 7. Seed coat cracked or burst. 8. Ungerminated seed P Polyembryony
Results of the main variables (monthly testing, moist chilling and photoperiod) were analyzed by analysis of variance for each species.
Figure 5 Results 12 monthly germination tests under 8-hour photoperiod of non-chilled and chilled Picea glauca, Pinus contorta and Pinus banksiana seeds. Figure 5 shows the significant differences in monthly total germination of the three species as affected by moist chilling and photoperiod. There were variations in total germination of non-chilled P. galuca and P.contorta seeds among the monthly test periods, however, the pattern was not consistent and the magnitude of the variation was relatively small (5-7% from the mean).
P. glauca Figure 5A Non-chilled seeds: Lower germination % in Apr. (1980) and Jan. to Mar. (1981). Higher germination % in Oct. to Dec. Moist chilled seeds: No difference (S.E. = 0.23).
P. contorta Figure 5B Non chilled seeds: Lover germination % in Jun. and Oct. Higher germination % in Jan, Aug and Nov. Moist chilled seeds: Little difference (S.E. = 0.37).
P. banksiana Non-chilled and moist chilled seeds: Little or no difference (S.E. = 0.1 - 0.17). Figure 5C Rate of Germination
12 monthly tests of germination rate of chilled and non-chilled Picea glauca, Pinus contorta and Pinus banksiana seeds (8-hour Photoperiod). Figure 6
P. glauca Non-chilled seeds: Faster rate germination May, Sept. Slower rate germination – Apr,Jun,Jul,Dec. Moist chilled seeds: No difference (S.E.= 0.18). Figure 6A
P. contorta Figure 6B Non-chilled seeds: Faster rate germination – Apr, May, Aug. Slower rate germination – Jun, Jul, Oct. Moist chilled seeds: Little difference (S.E. = 0.02).
P. banksiana Figure 6C Non-chilled seeds: All uniform except faster rate germination in Oct. and Dec. which was suspected as a result of human error. Moist chilled seeds: Completely uniform in rate of Germination (S.E. = 0.09).
Effect of Extended Photoperiod Figure 7 12 monthly germination tests under 16-hour photoperiod of chilled and non-chilled Picea glauca, Pinus contorta and Pinus banksiana seeds.
P. galuca Figure 7A Non-chilled seeds: Improved the total germination throughout the 12 monthly tests (S.E. = 0.38). The extended photoperiodic effect on germination was negated by moist chilling (S.E. = 0.37).
P. Contorta Figure 7B Over-all total germination of the non-chilled seeds was improved by the extended photoperiod, and variations among the 12 monthly tests were reduced. The higher germination occurred in Mar (89%), Apr (89%), May (88%), Nov (93%) and Dec (88%) and the lower germination in Jun., Jul. and Oct (85%). Extended photoperiod had no effect on the moist chilled seeds.
P. banksiana Extended photoperiod had no effect on jack pine seed germination; there was very little variation found among the 12 monthly tests (S.E. = 0.17). Figure 7C
Discussion and Conclusion Findings of this study could not confirm previous research results. Although there were significant variations in the rate and total germination among monthly germination tests of the non-chilled dormant Picea glauca and Pinus contorta seeds, they were eliminated or greatly reduced when the seeds were moist chilled for 21 days.
The variations among monthly tests of non-chilled seeds varied with species and did not follow any consistent pattern. It is most likely that these variations were caused by external than internal factors. There was very little or no variation among the monthly germination tests of the non-dormant Pinus banksiana seeds.
Moist chilling (or cold stratification) was proved to be not only as an efficient treatment for removing dormancy and also for minimizing external factors influencing germination.
Extended photoperiod was effective in improving total germination but cannot substitute for moist chilling. In view of the importance of this subject, more comprehensive in-depth research is warranted in the future.