Effects of Solution Nitrogen and Plant Density on Annual Grass Seed Biochemistry and Progeny Phenotypic Plasticity

Cogenerational phenotypic plasticity compensation to nutrient limitations and shoot densities (light limitation) among individual plants of the same species could provide an increased fitness. Planting density varying between 4 and 16 plants per container and solution nitrogen varying between 5 and 19 mM were used to test phenotypic plastic responses in oat (Avena sativa cv. Montezuma) seed biochemistry and the resulting progeny. Seed Kjeldahl nitrogen (N), magnesium (Mg), and both albumin-globulin (l M NaCl soluble) and prolamin-glutelin (residue) protein fractions were affected by a solution N × plant density interaction. Phosphorus (P) content was influenced by both treatment variables. The protein fractions, P, N, and Mg, in seeds from parent treatments were generally highest in the two higher planting densities. The contents of N, P, Mg, and the prolamin-glutelin fraction were highest at mid‐N (9 mM), except for the 16 plants per container where they were maximal at high-N (19 mM). In contrast, the albumin–globulin fraction responded linearly to N availability. Seeds per plant decreased while seed weights increased, as plant density increased. The seed content of N, albumin-globulin, prolamin-glutelin, P, and Mg were all negatively associated with the number of seeds per plant. Germination rates of progeny were inversely related to parent plants N treatment. Progeny from the treatment plants (seeds × germination percent) were inversely related, over a five‐fold range, to parent density. Progeny shoot/root ratios (S/R) were directly influenced by the N treatment of parent plants, with progeny from the highest parent N treatment having the highest S/R. Seed N and P content and the prolamin-glutelin protein fraction concentration were correlated with progeny SR. Seed weight was negatively correlated with progeny S/R. Annual grass seed numbers and weights and the allocation of several seed constituents are environmentally influenced by plant density and solution N. These seed biochemical and physiological effects result in a reproductive fitness change and a cogenerational phenotypic plasticity influenced progeny fitness (S/R attribute).