Final answer:
Stomata in plants close at night to avoid excessive water loss through transpiration. A signal transduction pathway is a mechanism that allows plants to respond to environmental signals and changes, resulting in stomatal opening or closure. The flow of water, nutrients, and sugars in a plant is driven by differences in water potential.
Step-by-step explanation:
Plants often close their stomata, the pores on plant surfaces, at night to prevent the excessive loss of water through transpiration which can happen if they were left open. This is because plants, unlike animals, cannot replenish lost water quickly. But stomatal closure results in a limitation in carbon dioxide (CO2) uptake for photosynthesis which primarily happens during the day.
Signal transduction pathway is a mechanism which allows cells to respond to environmental changes. When a specific light signal is captured by a plant’s photoreceptor, a signal transduction pathway is triggered causing the stomata to open up. On the other hand, under dehydration stress, the hormone Abscisic Acid (ABA) initiates a signal transduction pathway resulting in the closure of stomata to prevent water loss.
Water potential differentials in the plant body are the driving forces behind the movement of water, nutrients and sugars. Higher water potential in the roots as compared to the leaves drives the upward flow. The stomata’s opening and closing are also governed by water potential where a lower water potential outside results in the stomata closing to prevent water loss and vice versa.
Learn more about Plant Physiology