SEED MASS EFFECTS ON GERMINATION AND GROWTH OF DIVERSE EUROPEAN SCOTSPINE POPULATIONS

Seedlings of 24 European Scots pine (Pinus sylvestris L.) populations were grown in controlled environment chambers under simulated photoper iodic conditions of 50 and 60 degrees N latitude to evaluate the effec t of seed mass on germination and seedling growth characteristics. See ds of each population were classified into l-mg mass classes, and the four classes per population with the highest frequencies were used. Ph otoperiod had minimal influence on seed mass effects. Overall, seed ma ss was positively related to the number of cotyledons and hypocotyl he ight. Populations differed significantly in seed mass effect on biomas s. In northern populations (55-61 degrees N), dry mass at the end of t he first growing season was little affected by seed mass. However, dry mass in 9 of 15 central populations (54-48 degrees N) and all souther n (<45 degrees N) populations correlated positively with seed mass. Re lative growth rate was not related to seed mass within or across popul ations, and thus early growth is largely determined by seed mass. Rela tive growth rate also did not differ among populations, except for a g eographically isolated Turkish population with the highest seed mass a nd lowest relative growth. rate. After one growing season, height was positively correlated (r(2) > 0.6) with seed mass in 15 populations. T o check the duration of seed mass effects, height growth of 1- to 7-ye ar-old field experiments established with the same seed lots were comp ared. Seed mass effects on height were strongest for 1-year-old seedli ngs and declined or disappeared by the age of 5-7 years among central and southern populations, but remained stable over that time in northe rn populations.