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A large, evergreen tree, Cupressus × leylandii reaches a size between 20 and 25 m high, with its leaves giving it a compact, thick and regular habit. It grows very fast with yearly increases of 1 m. The leaves, about 1 mm long and close to the twig, are presented in flaky, slightly aromatic branches. They are dark green, somewhat paler on the ...
The plants thrive best in hot, damp and humid locations, such as the clearings of forests; but the leaves most preferred are obtained in drier areas, on the hillsides. The leaves are gathered from plants varying in age from one and a half to upwards of forty years, but only the new fresh growth is harvested.
Some are resprouters, and have a thick rootstock buried in the ground that shoots up new stems after a fire, and others are reseeders, meaning the adult plants are killed by the fire, but disperse their seeds, which are stimulated by the smoke to take root and grow. The heat was previously thought to have stimulated growth, but the chemicals in ...
Viburnum lesquereuxii leaf with insect damage; Dakota Sandstone (Cretaceous) of Ellsworth County, Kansas. Scale bar is 10 mm. Knowledge of herbivory in geological time comes from three sources: fossilized plants, which may preserve evidence of defense (such as spines) or herbivory-related damage; the observation of plant debris in fossilised animal feces; and the structure of herbivore mouthparts.
Many of these plants are used intentionally as psychoactive drugs, for medicinal, religious, and/or recreational purposes. Some have been used ritually as entheogens for millennia. [1] [2] The plants are listed according to the specific psychoactive chemical substances they contain; many contain multiple known psychoactive compounds.
Leaf movement is also controlled by bioactive substances known as leaf opening or leaf closing factors. Several leaf-opening and leaf-closing factors have been characterized biochemically. [5] These factors differ among plants. Leaf closure and opening is mediated by the relative concentrations of leaf opening and closing factors in a plant. [6]
A geophyte (earth+plant) is a plant with an underground storage organ including true bulbs, corms, tubers, tuberous roots, enlarged hypocotyls, and rhizomes. Most plants with underground stems are geophytes but not all plants that are geophytes have underground stems. Geophytes are often physiologically active even when they lack leaves.
Etiolation increases the likelihood that a plant will reach a light source, often from under the soil, leaf litter, or shade from competing plants. The growing tips are strongly attracted to light and will elongate towards it. The pale color results from a lack of chlorophyll. Some of the changes that occur include elongation of stems and leaves;