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Autumn leaf color is a phenomenon that affects the normally green leaves of many deciduous trees and shrubs by which they take on, during a few weeks in the autumn season, various shades of yellow, orange, red, purple, and brown. [1]
Want to know how and why leaves change color in the fall? We've got you covered, unlike the trees dropping leaves after creating lovely fall foliage.
The process of osmosis over a semipermeable membrane.The blue dots represent particles driving the osmotic gradient. Osmosis (/ ɒ z ˈ m oʊ s ɪ s /, US also / ɒ s-/) [1] is the spontaneous net movement or diffusion of solvent molecules through a selectively-permeable membrane from a region of high water potential (region of lower solute concentration) to a region of low water potential ...
This hyperpolarization of the membrane allowed the accumulation of charged potassium (K +) ions and chloride (Cl −) ions, which in turn, increases the solute concentration causing the water potential to decrease. The negative water potential allows for osmosis to occur in the guard cell, so that water enters, allowing the cell to become turgid.
The carotenoids and anthocyanin can now give off those spectacular fall colors. When and how the leaves change color depends on tree species – some have leaves that just turn brown and fall.
Osmoregulation is the active regulation of the osmotic pressure of an organism's body fluids, detected by osmoreceptors, to maintain the homeostasis of the organism's water content; that is, it maintains the fluid balance and the concentration of electrolytes (salts in solution which in this case is represented by body fluid) to keep the body fluids from becoming too diluted or concentrated.
Streptocarpus sp. leaf showing abscission line in response to reduced day length. The reduction of chlorophyll production in leaves due to decreased sunlight in the autumn explains why some leaves turn yellow. However, the yellow color can attract aphids, so some trees turn the leaves red instead by injecting a bright pigment. [8]
With much of the sucrose having been removed, the water exits the phloem by osmosis or is drawn by transpiration into nearby xylem vessels, lowering the turgor pressure within the phloem. [4] The sucrose concentration in sieve tubes is typically 10–30% in the leaves but only 0.5% in the photosynthesis cells.