Quantitative Characterization of Vegetative Development in Small Cereal Grains¹

Abstract The number of headed tillers is an important yield component in cereal grain production. Studies are needed to assess effects of environmental stress and genetic factors on tiller production and abortion in the field. The system for quantifying cereal leaf and tiller development described in this paper permits such studies to be done more definitively than was previously possible because each leaf and tiller on the plant is given a unique designation. The system developed on wheat [ Triticum aestivum (L.) em. Thell.] is suitable for other cereals. Leaves are numbered acropetally, with the first foliar leaf being L1 and the coleoptile L0. Tillers are named for the leaf with which they are associated, e.g., T1 and TO. Subtillers have two digit designations, and third order tillers have three digit designations. Culm development is described by counting the number of fully expanded leaves and the fraction of the length the newest developing leaf measures relative to its predecessor. A stem with 6.2 leaves has six fully developed leaves and a seventh leaf one‐fifth as long as the sixth. The developmental time or phyllochron for each leaf on the plant is the same in any given environment, and leaves and tillers unfold in a set and orderly pattern. The rate of this unfolding is primarily determined by environment. Stress causes tillers to be omitted or delayed, compared to unstressed plants.