Impact of high temperature on growth of embryo and germination of heteromorphic seeds of Anethum graveolens L. (Apiaceae)

Heteromorphism is widespread in nature and manifests itself in the variation of various parameters of seeds within individual individuals and populations. Dill ( Anethum graveolens L.) seeds are characterized by heteromorphism caused by the maternal factor. First of all, the maternal factor effects on the size of the seeds, in this case a variation in the size of the embryo can be observed. The study of the reaction of such seeds to the action of abnormal weather conditions is an urgent task. High temperature is one of the unfavorable abiotic factors that plants can be exposed to at different stages of development. In the present study, a significant thermal sensitivity to the long-term effect of suboptimal (higher than the optimal) temperature of embryos from dill seeds, formed in inflorescences of the second order of branching, was revealed for the first time. Under the influence of high temperature, the growth of embryos was inhibited. As a result, germination of intact dill seeds obtained from second-order inflorescences was observed. This work is devoted to the study of the effect of high temperature on the growth of the embryo and the germination of intact dill seeds obtained from different orders of branching. The study aimed to determine the influence of the maternal factor, as well as high temperature on the growth of the embryo during germination and on the germination of intact dill seeds formed in inflorescences of different orders of branching. The research was conducted in 2015-2016 at the All-Russian Research Institute for Vegetable Growing, Branch of the Federal Scientific Vegetable Center, with the late-ripening dill variety Centaur seeds, formed in inflorescences of the first and second orders of branching. The seeds were obtained from dill plants grown in the open field. Harvesting was carried out on day 50 after flowering of 1st order umbrellas. The experiments were carried out in a temperature-controlled thermostat. To determine the critical temperature for the growth of the embryo during germination and germination rate of intact seeds formed in different orders of branching, a wide temperature range was applied, 20 °С as control, and 25, 30, 35 and 40 °С. Using the morphometric method of analysis, we studied the growth of the embryo, as well as the dynamics of the germination of intact seeds against the high temperatures background. The data obtained were used to calculate the parameters and plot the embryo growth curve, as well as the germination curve of intact seeds. Logistic regression was used to calculate the maximum suboptimal temperature at which embryo growth and seed germination are possible. On the basis of experimental data, we have shown that embryos, formed at different branching orders of the mother plant, have different stages of development. The initial dimensions of the embryo of the first branching order are 30 % higher than the second (p function show_eabstract() { $('#eabstract1').hide(); $('#eabstract2').show(); $('#eabstract_expand').hide(); }