Plant Responses to Abiotic Stress
Photoperiodism
- Photoperiodism is a plant's sensitivity to lack of light in their environment.
- Photoperiodism is responsible for a variety of changes in plants such as dormancy of leaf buds, timing of flowering and tuber formation for overwintering.
Abscission in Deciduous Plants
- In temperate areas, such as the UK, daylight and temperature changes dramatically with the seasons, and this affect the rate of photosynthesis.
- In the winter, to survive, deciduous trees lose their leaves as the cost of glucose required to maintain the leaves and to produce antifreezing chemicals is greater than the glucose produced in photosynthesis in winter.
- When photosynthesis becomes efficient again, the leaves regrow.
Preventing Freezing
- In order to prevent freezing, after long periods of no light, plants actively transport salts into the vacuole and cytoplasm.
- This means that the freezing point is lowered, so the water will not expand as it freezes causing hydrogen bonds in the cellulose cell wall to be broken.
- This is why plants often die after a sudden frost, as they are unprepared. The cells burst as the turgor pressure created by the frozen water is too great, and when it defrosts the cells have no structure.