Dill seed germ development after short-term temperature stress.

NNew data on germ growth processes of dill seeds formed at the first and second branching orders after exposure to short-term heat stress (40 °C) are presented. Morphometric method and analysis of dill seed embryo growth in dynamics were used. The studies were carried out in 20152017 at the All-Russian Research Institute of Vegetable Growing, a branch of FSBSI FSCVG. Seeds of dill (Anethum graveolens L.) of the variety Centaurus from the first and second branching orders were the object of research. First, seeds were germinated in a thermostat. Then, swollen roots were exposed to a temperature of 40 °C according to the experiment scheme: 0 (control); 1; 2; 3; 4 and 5 days. After incubation, the seeds were transferred to standard conditions (temperature 20 °C) and germinated in Petri dishes on filter paper without light for 21 days. Germ size was measured using image analysis software. Critical embryo length and degree of underdevelopment were determined, and the ratio of embryo length to endosperm length (I _Z/E) was calculated. Logistic regression with four parameters: b, c, d, e., was used to construct a germ growth curve. The relationship between the parameters was assessed using Pearson correlation analysis. The differences were considered statistically significant at P≤0.05. The duration of temperature action, which has an inhibitory effect on embryo growth, germination rate, the number of germinated seeds, were revealed. It was found that the embryos of seeds obtained from different branching orders have different sizes and have different intensity of growth under stress and standard conditions. It was shown that the effect of brief temperature (40 °C) on embryo growth depends on branching order and that embryos of seeds of the second branching order are more sensitive to high temperature. Morphometric parameters of the source were shown to play a critical role in the ability of dill seeds to resist the effect of temperature stressor during germination.

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