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Sieve tube element. Sieve elements are specialized cells that are important for the function of phloem, which is a highly organized tissue that transports organic compounds made during photosynthesis. Sieve elements are the major conducting cells in phloem. Conducting cells aid in transport of molecules especially for long-distance signaling.
Pollen tube. SEM image of pollen tubes growing from lily pollen grains. A pollen tube is a tubular structure produced by the male gametophyte of seed plants when it germinates. Pollen tube elongation is an integral stage in the plant life cycle. The pollen tube acts as a conduit to transport the male gamete cells from the pollen grain —either ...
This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms.It is intended as introductory material for novices; for more specific and technical definitions from sub-disciplines and related fields, see Glossary of cell biology, Glossary of genetics, Glossary of evolutionary biology, Glossary of ecology ...
A taxis (from Ancient Greek τάξις (táxis) 'arrangement, order'; [1] pl.: taxes / ˈtæksiːz /) [2][3][4] is the movement of an organism in response to a stimulus such as light or the presence of food. Taxes are innate behavioural responses. A taxis differs from a tropism (turning response, often growth towards or away from a stimulus) in ...
The cell is the basic structural and functional unit of all forms of life. Every cell consists of cytoplasm enclosed within a membrane; many cells contain organelles, each with a specific function. The term comes from the Latin word cellula meaning 'small room'. Most cells are only visible under a microscope.
Biology is the scientific study of life. [ 1 ] [ 2 ] [ 3 ] It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. [ 1 ] [ 2 ] [ 3 ] For instance, all organisms are made up of cells that process hereditary information encoded in genes , which can be transmitted to future ...
The pressure flow hypothesis, also known as the mass flow hypothesis, is the best-supported theory to explain the movement of sap through the phloem of plants. [1][2] It was proposed in 1930 by Ernst Münch, a German plant physiologist. [3] Organic molecules such as sugars, amino acids, certain hormones, and messenger RNAs are known to be ...
Biological rules. The pygmy mammoth is an example of insular dwarfism, a case of Foster's rule, its unusually small body size an adaptation to the limited resources of its island home. A biological rule or biological law is a generalized law, principle, or rule of thumb formulated to describe patterns observed in living organisms.