The cold desert annual grass Eremopyrum distans exhibits position-dependent effects of seeds in the spikelet. Wang et al. (pp. 95–105) find that seeds from three positions in a spikelet differ in morphology, mass and in percentage and rate of seed germination, and the plants derived from them differ in growth and seed production. Distal seeds appear to represent a ‘high-risk’ life history strategy and basal seeds a ‘low-risk’ strategy.
A. B. Wang, D. Y. Tan, C. C. Baskin, J. M. Baskin, 2010, 'Effect of seed position in spikelet on life history of Eremopyrum distans (Poaceae) from the cold desert of north-west China', Annals of Botany, vol. 106, no. 1, pp. 95-105 http://dx.doi.org/10.1093/aob/mcq089