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Found Internal Thermometer Tells Seeds When To Germinate

Researchers have figured out how seeds make temperature-dependent decisions about whether to remain dormant or to begin germination.

A plant must go through germination in order to move from the seed stage, which is resistant to numerous environmental constraints (climate, lack of nutritional materials, etc.), to the seedling stage, which is considerably more fragile. The timing of this shift will determine whether the young plant survives. Therefore, it is crucial that this stage be carefully managed. Researchers from the University of Geneva (UNIGE) in Geneva, Switzerland, have shown that seeds include an internal thermometer that, if temperatures rise too high for the future seedling, might hinder or even prevent germination. This work might aid in optimizing plant growth in relation to climate change.

Seeds that have just been produced are dormant and incapable of germination. The seeds awaken and develop the potential to germinate during the ideal season for seedling growth and fresh seed production after a few days (or even months, depending on the species). Non-dormant seeds can still control their destiny, nevertheless. For instance, a non-dormant seed that is suddenly exposed to temperatures that are too high (>28°C) may be prevented from germinating. This temperature-induced inhibitory mechanism (thermo-inhibition) enables extremely precise regulation. A seed population’s germination can be delayed by 1 to 2°C, increasing the likelihood that successive seedlings will survive.

Phytochrome B is a crucial protein.
In many research projects, the plant species Arabidopsis thaliana, which is a member of the Brassicaceae family, is used as a model. Luis Lopez-Molina, a professor at the Department of Plant Sciences of the Faculty of Science of the UNIGE, is working with a group interested in understanding how germination is controlled in this plant species. Scientists investigated a series of events that had already been documented and were relatively similar in young plants, i.e. at a more advanced stage of development, in order to understand the detecting mechanisms that allow seeds to initiate thermo-inhibition.

Certainly, seedlings can sense temperature changes, and a tiny rise in temperature encourages the growth of stems in them. This adaptation resembles the one seen in plants when they are in another plant’s shadow: they extend to get out of the shadow and expose themselves to the sunshine, which is better for photosynthesis. Phytochrome B, a protein sensitive to light and temperature that typically slows plant growth, is able to detect these differences. Phytochrome B is inactivated by a temperature increase of 1 to 2°C, which reduces its ability to inhibit growth.

Source (SciTechDaily)

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