In forage grasses yield components that determine the extent of biomass accumulation are the number of tillers per area and the weight of an individual tiller. The maximum light interception and net assimilation is achieved when the canopy consists of tall, stem forming tillers. Those tillers are also heavy, contributing significantly to the accumulating biomass.
Our studies have shown that at a rapid stage of biomass accumulation in spring, the development of tillers is synchronized by vernalization and the proportion of flowering stems in the yield is high. Similarly to winter cereals, VRN1 has a key role in a transition of apices from vegetative leaf forming stage to generative stage producing flowering structures.
It is thought that flowering causes a rapid decrease in digestibility and nutritive value of harvested forage biomass due to lignification of the stem. We followed the development of apices and stem elongation in field conditions and studied it's relationship to development of lignified schlerenchyma ring. Our studies showed that transition to generative stage is not necessary for the initiation of extensive stem lignification but rather the height of the stem was important. Together with our colleques in Luke Maaninka we identified a third tiller type in timothy so called elongating tiller, where stem elongation had initiated without flowering stimulus. These elongating tillers contribute significantly to summer and autumn yields and their digestibility decreases as the stem elongation proceeds.