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T-tubules (transverse tubules) are extensions of the cell membrane that penetrate into the center of skeletal and cardiac muscle cells.With membranes that contain large concentrations of ion channels, transporters, and pumps, T-tubules permit rapid transmission of the action potential into the cell, and also play an important role in regulating cellular calcium concentration.
Early seed plants like ferns have spores and motile sperm that swim in a water medium, called zooidogamy. [18] The angiosperm pollen tube is simple, unbranched, and fast growing, however this is not the case for ancestral plants. In gymnosperms like Ginkgo biloba and cycadophyta, a haustorial pollen tube forms. The tube simply soaks up ...
Some plants also form smaller tubers or tubercules that act like seeds, producing small plants that resemble (in morphology and size) seedlings. Some stem tubers are long-lived, such as those of tuberous begonias , but many plants have tubers that survive only until the plants have fully leafed out, at which point the tuber is reduced to a ...
A T-tubule surrounded by two terminal cisternae is called a triad. The terminal cisternae, along with the transverse tubules, are the mechanisms of transduction from a nervous impulse to an actual muscle contraction .
The z-line defines the borders of each sarcomere and act as the connection point between the thin filaments. The t-tubules and sarcoplasmic reticulum are used in conjunction to receive and direct the calcium ions and cause contraction. Once contracted, the clear H-zone between the actin filaments disappears as the filaments move towards each other.
A germination rate experiment. Plant physiology is a subdiscipline of botany concerned with the functioning, or physiology, of plants. [1]Plant physiologists study fundamental processes of plants, such as photosynthesis, respiration, plant nutrition, plant hormone functions, tropisms, nastic movements, photoperiodism, photomorphogenesis, circadian rhythms, environmental stress physiology, seed ...
Hypersensitive response (HR) is a mechanism used by plants to prevent the spread of infection by microbial pathogens.HR is characterized by the rapid death of cells in the local region surrounding an infection and it serves to restrict the growth and spread of pathogens to other parts of the plant.
In plant anatomy, there are two main types of sieve elements. Companion cells and sieve cells originate from meristems , which are tissues that actively divide throughout a plant's lifetime. They are similar to the development of xylem , a water conducting tissue in plants whose main function is also transportation in the plant vascular system ...