![]() This type of plant movement is caused by a number of different phenomena. Sunflowers are known for a peculiar behavior in which their flowers not only track the sun but their petals also droop and close slightly during the evening and nighttime hours. Just as an example, if you’ve ever gardened outdoors and have grown sunflowers, you’ll understand exactly what nyctinastic movement looks like. If you’re wondering how to increase humidity in a room to keep your plants perky, one of the easiest and cheapest ways is to set a tray of water in a sunny, warm place, and refill every few days. Subsequently, day turning to night is the stimuli that halt water uptake, slows osmosis, and closes most of a plant’s stomata, leaving it looking wilted and droopy.Īnd when the sun rises again and night turns to day, diurnal light (the opposite of nocturnal darkness) and an increase in temperature and humidity cause a plant to “wake up”, open its leaves and flowers, and welcome the new day looking stiff, attentive, and healthy. This change in a plant’s environment acts as stimuli, signaling to the plant that it is time to wind down and rest for the night. This circadian rhythm impacts many of a plant’s biological and physiological processes including leaf movement, growth, reproduction, stomatal gas exchange, and will even determine the direction a flower faces.Īnd just like any other organism, for a plant’s circadian rhythm to work, it is dependent on its surrounding environment for stimuli.įor instance, when daytime turns to nighttime the temperature falls and the sun goes down. Nyctinastic movement, the circadian rhythmic movement of higher plants (those that have evolved vascular tissue unlike algae and Bryophytes), follows both the daytime and nighttime hours and responds to the onset of darkness. Just like you and me, plants have a circadian rhythm, a phenomenon known as nyctinasty. This is what causes a plant to appear wilted at night, there is more evaporation occurring than there is liquid uptake. So instead, the plant stops absorbing water through its roots and enters somewhat of a “sleep” stage. Well, during the night there is no sunlight to drive photosynthesis or most other metabolic processes that produce gases and evapotranspiration. On the other hand, if a plant is unable to uptake enough water because there simply isn’t enough available or because it’s nighttime and the plant discontinues respiration, it will close most of its stomata, slowing osmosis, and begin to appear wilted.Īnd why does a plant stop respiring during the evening hours? Other water-using plant metabolic processes produce a number of by-products, some being oxygen, which is released through very small holes existing on the bottom of a plant’s leaves.ĭuring the daylight hours, assuming the plant is able to uptake sufficient amounts of water, through the process of osmosis stomata open to allow respiration and ultimately evapotranspiration (a process of transpiration and subsequent evaporation of plant produced gases into the atmosphere).Īnd if available, the plant will continue to absorb slightly more water than it can respire, making the plant appear turgid and healthy. It’s what gives a plant its rigid, stiff, and healthy look. Turgor pressure is the pressure that is exerted by fluids against the cell membranes of a plant. ![]() One such metabolic process causes something called turgor pressure. So why does this happen? Well, water that is taken up through a plant’s roots is subsequently used in a variety of metabolic processes. The less a plant absorbs water through its roots the more flaccid, wilted, or droopy it will appear, a phenomenon that usually occurs during the nighttime. The higher the uptake in water, something that occurs during the day, the more turgid or stiff a plant appears.Īnd the opposite is also true. Turgidity, or its opposite flaccidity, is caused by the amount of water that is being taken up by a plant’s root system. ![]() ![]() In fact, a drooping plant can be caused by something called turgidity, or lack thereof. Drooping leaves that are observed at night or during the evening isn’t necessarily a sign that a plant is unwell.
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