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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Click on a letter to see definitions of all words beginning with that letter.L
Labium - a lip.
Lacteus - milky.
Lamella - a thin plate or layer.
Lamina - the blade or expanded part of a leaf.
Lanate - with long, soft wooly hairs.
Lanceolate - shaped like a long narrow lance with a gradual taper from the base to the tip.
Lasiacantha - with shaggy or hairy spines.
Lateral-
growing or positioned at the sides.
Latex - a milky aqeous emulsion containing a variety of organic substances, often including rubber and various proteins. Commercially, latex produced from within bark of the rubber tree is coagulated by heat to produce natural rubber.
Laticifer - cells containing a characteristic milky fluid called latex.
Leaf - an outgrowth from a node on a plant's stem. Leaves come in many shapes and sizes, but are often flattened to maximise their surface area for capture of energy from sunlight (photosynthesis) using chlorophyll contained in chloroplasts, thin to allow light to penetrate the tissues and oriented to optimise exposure to sunlight. In most plants, leaves also allow gas exchange, guttation, respiration and transpiration to take place. Leaves can store food and water and may be modified for other purposes.
See also:
- leaf blade: simple, compound, palmate, peltate, pinnate, trifoliate
- leaf arrangement on the stem: alternate, decussate, distichous, opposite, rosulate, spiral, whorled
- leaf margins: ciliate, crenate, crenolate, dentate, entire, guttered, serrate, sinuate, teeth
- leap tip: acuminate, drip tip, emarginate, hooked, lanceolate, mucro, mucronate, spatulate
Leaflet - part of a compound leaf.
Lectin - a diverse group of plant proteins capable of aglutinating cells (such as red blood cells). Lectins contain sites that recognise and bind to sugar residues, such as those included in the structure of glycoproteins. Ricin is a notorious toxic lectin from the seeds of the castor oil plant.
Lectotype - a specimen selected from the original type material to serve as the nomenclatural type when a holotype was not originally designated, or is missing.
Leggy - of plants exhibiting excessive, rank growth, often caused by excessive watering, application of fertiliser or insufficient light.
Legume -
i. a fruit with a single compartment that splits along two sutures or seams e.g. pea pod.
ii. a plant in the family Leguminosae (peas, beans) that can fix nitrogen from the soil due to the presence of symbiotic bacteria (e.g. Rhizobium species,) in root nodules.
Lenticel - a pore in tree bark through which gas exchange occurs.
Lenticular - shaped like a biconvex lens.
Leptocaulis - with slender stems.
Liana - liane- a woody, climbing vine.
Lichen - a complex differentiated organism formed by a symbiotic relationship between an algae and a fungus.
Lignin - a diverse group of non-toxic organic polymers often associated with cellulose in the walls of many plant cells, especially in woody plants. In this form, lignin acts as a cement to exploit the strength of cellulose fibres, while allowing flexibility. The mechanical properties of this natural composite material (wood) compare favourably with many man-made composite materials such as fibre-glass. After cellulose, lignin may be the second most abundant biopolymer in the world with an estimated annual production of 108 tons, but see also chitin.
Lignin is formed by the irreversible removal of water from sugar monomers to create phenolic aromatic structures. Polymerisation and extensive cross-linking occur to create very large three-dimensional lignin molecules. Sometimes lignin is isolated as a brown powder, but more often as a gummy mixture of lignins with a wide range of molecular weights. Lignin resists attack by most microorganisms, and anaerobic processes tend not to attack the aromatic rings at all. Aerobic breakdown of lignin is slow and may take many days. Hence, the presence of lignin strongly affects the bio-degradeability of woody materials such as straw.
Linear - long and narrow with parallel or nearly parallel sides.
Linnaeus - Carolus Linnaeus (1707-1778) - a Swedish scientist who devised the binomial nomenclature used to identify every living species. The Linnaean System of classification is based on a simple hierarchical structure in which all known organisms are listed according to Kingdom, Phylum, Class, Order, Family, Genus and Species.
Lithophyte - growing on rocks.
Littoral - growing on the beach.
Litteralis - belonging to the sea shore.
Lobe - partial rounded portion of a leaf or other organ, separated from the whole by a deep indentation that does not break the continuity of the structure.
Lobed flower - a tubular or funnel-shaped flower opening into petal-like segments.
Locule - individual compartment of an anther, ovary or fruit.
Loculicidal - longitudinally dehiscent along the capsule wall between the partitions of the locule so as to split it into two parts, as in the fruits of Liliaceae.
Lumen -
i. A pore or passage through a tubular structure.
ii. an internal cavity, space or void. e.g. cavity within the plant cell cell wall.
iii. the SI measurement of light output (or luminous flux) used to label light sources as a measure of total light output. 1 lumen (lm) = 0.00146 W.
A unit of luminous flux equal to the amount of light given out through a solid angle of 1 steradian by a point source of 1 candela intensity radiating uniformly in all directions.
Lumper - coloquial - one who takes a broad view of a genus, combining variant forms into individual species.
Lutescens - yellowish.
Lycorine - a toxic alkaloid found in Amaryllidaceae (daffodil family) all members of which should be regarded as poisonous. Poisoning by daffodil bulbs, confused with onions, is fairly common. Symptoms of ingestion include salivation, vomiting, diarrhea, collapse and death, depending on the dose. Lycorine inhibits protein synthesis and cell division and is of interest as an anti-tumour agent.
Structure of Lycorine
