Metals in general reflect all of the light energy that comes onto them but copper doesn't reflect all of them. It absorbs part of the spectrum. It absorbs the blue part of the light and maybe some of the green light and reflects all the coppery colored light which comes back into our eyes. That's what happens with the metal. The green pigment in leaves is chlorophyll, which absorbs red and blue light from sunlight. Therefore, the light the leaves reflect is diminished in red and blue and appears green. The molecules of chlorophyll are large (C55H70MgN4O6). They are not soluble in the aqueous solution that fills plant cells. Instead, they are attached to the membranes of disc-like structures, called chloroplasts, inside the cells. Chloroplasts are the site of photosynthesis, the process in which light energy is converted to chemical energy. In chloroplasts, the light absorbed by chlorophyll supplies the energy used by plants to transform carbon dioxide and water into oxygen and carbohydrates, which have a general formula of Cx(H2O)y. In this endothermic transformation, the energy of the light absorbed by chlorophyll is converted into chemical energy stored in carbohydrates (sugars and starches). This chemical energy drives the biochemical reactions that cause plants to grow, flower, and produce seed. Chlorophyll is not a very stable compound; bright sunlight causes it to decompose. To maintain the amount of chlorophyll in their leaves, plants continuously synthesize it. The synthesis of chlorophyll in plants requires sunlight and warm temperatures. Therefore, during summer chlorophyll is continuously broken down and regenerated in the leaves. Another pigment found in the leaves of many plants is carotene. Carotene absorbs blue-green and blue light. The light reflected from carotene appears yellow. Carotene is also a large molecule (C40H36) contained in the chloroplasts of many plants. When carotene and chlorophyll occur in the same leaf, together they remove red, blue-green, and blue light from sunlight that falls on the leaf. The light reflected by the leaf appears green. Carotene functions as an accessory absorber. The energy of the light absorbed by carotene is transferred to chlorophyll, which uses the energy in photosynthesis. Carotene is a much more stable compound than chlorophyll. Carotene persists in leaves even when chlorophyll has disappeared. When chlorophyll disappears from a leaf, the remaining carotene causes the leaf to appear yellow. A third pigment, or class of pigments, that occur in leaves are the anthocyanins. Anthocyanins absorb blue, blue-green, and green light. Therefore, the light reflected by leaves containing anthocyanins appears red. Unlike chlorophyll and carotene, anthocyanins are not attached to cell membranes but are dissolved in the cell sap. The color produced by these pigments is sensitive to the pH of the cell sap. If the sap is quite acidic, the pigments impart a bright red color; if the sap is less acidic, its color is more purple. Anthocyanin pigments are responsible for the red skin of ripe apples and the purple of ripe grapes. A reaction between sugars and certain proteins in cell sap forms anthocyanins. This reaction does not occur until the sugar concentration in the sap is quite high. The reaction also requires light, which is why apples often appear red on one side and green on the other; the red side was in the sun and the green side was in shade. During summer, the leaves are factories producing sugar from carbon dioxide and water using by the action of light on chlorophyll. Chlorophyll causes the leaves to appear green. (The leaves of some trees, such as birches and cottonwoods, also contain carotene; these leaves appear brighter green because carotene absorbs blue-green light.) Water and nutrients flow from the roots, through the branches, and into the leaves. Photosynthesis produces sugars that flow from the leaves to other tree parts where some of the chemical energy is used for growth and some is stored. The shortening days and cool nights of fall trigger changes in the tree. One of these changes is the growth of a corky membrane between the branch and the leaf stem. This membrane interferes with the flow of nutrients into the leaf. Because the nutrient flow is interrupted, the chlorophyll production in the leaf declines and the green leaf color fades. If the leaf contains carotene, as do the leaves of birch and hickory, it will change from green to bright yellow as the chlorophyll disappears. In some trees, as the sugar concentration in the leaf increases, the sugar reacts to form anthocyanins. These pigments cause the yellowing leaves to turn red. Red maples, red oaks, and sumac produce anthocyanins in abundance and display the brightest reds and purples in the fall landscape. The range and intensity of autumn colors is greatly influenced by the weather. Low temperatures destroy chlorophyll, and if they stay above freezing, promote the formation of anthocyanins. Bright sunshine also destroys chlorophyll and enhances anthocyanin production. Dry weather, by increasing sugar concentration, also increases the amount of anthocyanin. So the brightest autumn colors are produced when dry, sunny days are followed by cool, dry nights. The secret recipe. Nature knows best. Normally I'd keep a 10-degree swing between day and night but ripening will see the gap increase dramatically on this one. Anthocyanin color is highly pH-sensitive, turning red or pink in acidic conditions (pH 7) Acidic Conditions (pH 7): Anthocyanins tend to change to bluish or greenish colors, and in very alkaline solutions, they can become colorless as the pigment is reduced. The color changes are due to structural transformations of the anthocyanin molecule in response to pH changes, involving the protonation and deprotonation of phenolic groups. Anthocyanins, responsible for red, purple, and blue colors in plants, differ from other pigments like carotenoids and chlorophylls because their color changes with pH, making them unique pH indicators, while other pigments are more stable in color. Anthocyanins are a whole family of plant pigments. They are present in lilac, red, purple, violet or even black flower petals. Anthocyanins are also found in fruits and vegetables, as well as some leaves. Cold weather causes these purple pigments to absorb sunlight more intensely, which, in turn, raises the core temperature of the plant compared to that of the ambient air. This protects the plant from cold temperatures. In hot weather or at high altitudes, anthocyanins protect the plant cells by absorbing excessive ultraviolet radiation. Furthermore, a vivid petal coloration makes it easier for insects to find the flowers and pollinate them. Adding NaHSO4 (sodium hydrogen sulfate) to water increases the number of protons H+ in the solution. In other words, we increase the acidity of the medium because sodium hydrogen sulfate dissociates in water, or, in other words, it breaks down into individual ions: NaHSO4 → HSO4- + Na+ HSO4- SO42- + H+ In turn, the H+ protons react with the anthocyanin molecules transforming them from the neutral into cationic form. The cationic form of anthocyanins has a bright red color. The color of anthocyanins is determined by the concentration of hydrogen ions H+. When we add the sodium carbonate Na2CO3 solution, the H+ concentration drops. A decrease in the number of H+ causes a pigment color change, first to purple and then to blue and dark green. Anthocyanins are unstable in a basic environment, and so they gradually decompose. The decomposition process produces yellow-colored substances called chalcones. This process is quite slow, allowing us to track how a solution changes its color from blue to various shades of green and finally to yellow. The best petals would be brightly colored dark petals of red, purple, blue, or violet. You are particularly lucky if you can get your hands on almost black petals from either petunia, roses, irises, African violets, tulips, or lilies. These flowers contain a maximum concentration of anthocyanins. British scientist Robert Boyle (1627–1691) made a number of remarkable discoveries in chemistry. Interestingly, one of these discoveries involved the beautiful flowers known as violets. One day, Boyle brought a bouquet of violets to his laboratory. His assistant, who was performing an experiment at the time, accidentally splashed some hydrochloric acid on the flowers. Worried that the acid would harm the plants, the assistant moved to rinse them with water, but Boyle suddenly stopped him. The scientist’s attention was fixed on the violets. The places where acid had splashed the petals had turned from purple to red. Boyle was intrigued. “Would alkalis affect the petals, too?” he wondered and applied some alkali to a flower. This time the petals turned green! Experimenting with different plants, Boyle observed that some of them changed colors when exposed to acids and alkalis. He called these plants indicators. By the way, the violet color of the petals is produced by anthocyanins – pigments that absorb all light waves except violet. These vibrant pigments help attract bees, butterflies, and other pollinators, facilitating the flower’s reproduction. Anthocyanins are a type of flavonoid, a large class of plant pigments. They are derived from anthocyanidins by adding sugars. Sugars, particularly sucrose, are involved in signaling networks related to anthocyanin biosynthesis, and sucrose is a strong inducer of anthocyanin production in plants. Sugar-boron complexes, also known as sugar-borate esters (SBEs), are naturally occurring molecules where one or two sugar molecules are linked to a boron atom, and the most studied example is calcium fructoborate (CaFB). Boron is a micronutrient crucial for plant health, playing a key role in cell wall formation, sugar transport, and reproductive development, and can be deficient in certain soils, particularly well-drained sandy soils. Narrow Range: There's a small difference between the amount of boron plants need and the amount that causes toxicity. Soil concentrations greater than 3 ug/ml (3ppm) may indicate potential for toxicity. Anthocyanins, the pigments responsible for the red, purple, and blue colors in many fruits and vegetables, are formed when an anthocyanidin molecule is linked to a sugar molecule through a glycosidic bond. Glycosidic bonds are covalent linkages, specifically ether bonds, that connect carbohydrate molecules (saccharides) to other groups, including other carbohydrates, forming larger structures like disaccharides and polysaccharides. Formation: Glycosidic bonds are formed through a condensation reaction (dehydration synthesis) where a water molecule is removed, linking the hemiacetal or hemiketal group of one saccharide with the hydroxyl group of another molecule. Types: O-glycosidic bonds: The most common type, where the linkage involves an oxygen atom. N-glycosidic bonds: Less common, but important, where the linkage involves a nitrogen atom. Orientation: Glycosidic bonds can be alpha or beta, depending on the orientation of the anomeric carbon (C-1) of the sugar. Alpha (α): The hydroxyl group on the anomeric carbon is below the ring plane. Beta (β): The hydroxyl group on the anomeric carbon is above the ring plane. Disaccharides: Lactose (glucose + galactose), sucrose (glucose + fructose), and maltose (glucose + glucose) are examples of disaccharides linked by glycosidic bonds. Polysaccharides: Starch (amylose and amylopectin) and glycogen are polysaccharides formed by glycosidic linkages between glucose molecules. Significance: Glycosidic bonds are crucial for forming complex carbohydrates, which play vital roles in energy storage, structural support (like in cell walls), and as components of important biomolecules like glycoproteins and glycolipids.