Parental effects in plantago lanceolata L .2. Manipulation of grandparental temperature and parental flowering time

In an experimental study of Plantago lanceolata L., postzygotic environmentally induced parental effects were (1) transmitted across generations, (2) genotype-specific, and (3) mediated by natural differences in flowering phenology. Individuals were cloned, hand-pollinated and allowed to mature seed at one of two temperatures. Second-generation plants were induced to seed-set at four times during the flowering season. The effects of grandparental temperature (GPT), parental flowering time (PFT) and maternal family (MFAM) on seed size, germination, leaf area and allometry, flowering time and male sterility in third generation plants were then measured. GPT significantly affected all adult traits and did so more strongly than and often independently of seed weight and germination. The data suggest that heritable GPT effects arise from gametophytic selection or genomic modification. Significant GPT x MFAM interactions were detected for seed weight, leaf area, flowering time, and male sterility. Such genotype-specific responses are necessary if parental temperature is to influence the evolutionary divergence of life history and breeding patterns in populations growing in different temperature regimes. PFT affected leaf area and percentage germination. Natural changes in photoperiod but not temperature may explain the observed PFT effects on germination.