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 ofGermination in late summer or early fall and increasesIn the spring – usually April or May.

Figure3A

In contrast, no significant seasonal variations in germination were found of Pinus sylvestris seeds from 26 Soviet sources (Rostovtsev et al. 1975).

©Pinus sylvestris Photo copyright Kevin Bailey 2000 2003

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 andSeems to be regulated in the embryo; probablyrelated 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, physicaland physiological characteristics of the seeds.

Table 1

All cones were collected, processed andstored according to established proceduresof 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 topof blotter paper with a layer of Kimpak underneathin plastic germination boxes and stored at 2-4°Cin the dark for 21 days. Germination tests were carried out by moving the moist chilled seedsfrom cold room to Conviron G30 germinators at20°/30°C night/day temperatures with an 8- or 16- hour photoperiod.

Total germination was evaluated by the vigor class1 - 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 CentrePetawawa National Forestry

InstituteCanadian Forest Service

Chalk River, Ontario.

LABORATORY GERMINATION VIGOUR CLASSES FOR CONIFEROUS SEEDSHIGH VIGOUR LOW VIGOUR

1.Seed coatCompletelyShed.

2.Seed coatAlmost shed.

3.Seed coatSlightly shed 4.

HypocotylRaised butCotyledonsnot yet visible

5.Hypocotylraised butheightshorterthan thatin Class #4.

6. Radical emergedbut littlehypocotylvisible.

ABNORMALGERMINATION

Cotyledons

UNUSUAL GERMINATION

7.Seed coatcracked orburst.

8.Ungerminatedseed

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

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 previousresearch results.

Although there were significant variations in the rateand total germination among monthly germinationtests of the non-chilled dormant Picea glauca and Pinus contorta seeds, they were eliminated or greatlyreduced 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-dormantPinus 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 factorsinfluencing germination.

Extended photoperiod was effective in

improving total germination but cannot

substitute for moist chilling.

In view of the importance of this subject, morecomprehensive in-depth research is warrantedin the future.