Response of Plantago major seeds to the red/far-red ratio as influenced by other environmental factors

Seeds of Plantago major L. ssp. major were exposed to continuous light of various red/far-red ratios (R/FR). Germination was strongly inhibited at low R/FR. The quantitative response of the seeds to the R/FR appeared to depend on various environmental factors. A low R/FR was less inhibitory after a stratification pretreatment, at higher temperatures, in the presence of nitrate and at high osmotic potentials. This is discussed in relation to the concept of a variable requirement of P_fr for germination, which depends on state of dormancy as influenced by pretreatment and on conditions during the germination test. The data are also discussed in relation to field emergence. The species is known to form a persistent seed bank, among other things due to its almost absolute light requirement. It is predicted that germination is effectively inhibited under a leaf canopy in summer after dispersal, and perhaps even in spring to some extent when R/FR is not so low but temperatures are low.