Acronyms and Glossary of Rice Related Terminology Updated November 27, 2002

J Terms

japonica rice. One of the two major ecogeographical races of O. sativa (see also indica).A group of rice varieties from northern and eastern China grown extensively in some areas of the world. It has narrow, dark green leaves, medium-height tillers and short to intermediate plant stature. It is found in the cooler zones of the subtropics and in the temperate zones. Grains are short, roundish, spikelets awnless to long-awned, panicles low-shattering, and have 0-20% amylose content.

jarosite. An ocher-yellow or brown mineral consisting of basic sulfate of potassium and iron and occurring in minute rhombohedral crystals or in masses. Found in acid sulfate soils.

javanica rice. Designation for the bulu and gundil varieties of Indonesia and many upland rices. They belong to the japonica race of O. sativa. Rice varieties with broad, stiff, light green leaves. It is low-tillering and has a tall plant stature. Grains are long, broad, and thick, awned or awnless. Javanica grains are low-shattering and have 0-25% amylose content.

jointed. Constricted at intervals.

juvenile stage. The immature or young growth period.

K Terms

kairomone. The kind of allelochemicals that gives an adaptive advantage to the insect.

karyotype. The image of the entire chromosome set of an organism.

keel. The middle nerve of the lemma. The two lower united petals of a legume flower.

keeled. 1). With a ridge along the middle; with a ridge like the bottom of a boat.

kernel. The grain or seed of cereal or grass enclosed in a hard husk.

kernel moisture. The moisture of the dehusked grain.

kernel smut. A fungal disease that affects the kernels of rice and caused by Tilletia barclayana.

kilobase or kilo base pairs . A unit of size of DNA which is equal to either 1000 bases in a single-stranded nucleic acid (kb) or 1000 base pairs in a double-stranded nucleic acid (kbp).

kilogram. A metric measurement of weight equal to 1000 grams or the mass of one liter of water at 4 °C.

kneeing. The ability of the upper stem of deepwater or floating rice plants to bend upward after water has receded.

kresek. The Indonesian term for the systemic phase of the disease called bacterial blight at the seedling stage.

L Terms

label. Attachment used for identification purposes in field trials. Can also refer to incorporated radioactive marker.

labile. A substance that readily undergoes transformation or is readily available to plants.

labile genes. Genes that are always mutating.

labor market. The availability of people for work, e.g. in the ricefields.

lag phase. First stage of the sigmoidal growth curve where growth declines within a brief span of time.

lag phase (vegetative). That portion of the vegetative phase affected by the photoperiod to which the plant is exposed. The period from end of basic vegetative phase to panicle initiation; also called photoperiod-sensitive phase.

LAI. leaf area index; the sum of leaf area of all leaves divided by the ground area covered by the leaves.

lamina. The leaf blade.

lanceolate. 1). Lance-shaped, several times longer than wide; widest towards the base and tapering at both ends. 2). Lance shaped, much longer than broad, widening above the base, and tapering to the apex.

landform. The morphology and specific character of the land surface resulting from the interaction of physical processes and the earth's crustal movements with the geology of the surface layers.

land equivalent ratio (LER). The area needed under sole cropping to produce the same amount as 1 ha of intercropping or mixed cropping.

land preparation. The process of preparing the soil for planting, to provide a soil environment favorable for plant germination and/or growth.

land race. A traditional variety of rice endemic to a given location.

landscape. The overall surface form of an area including both natural and man-made features; it includes various landforms among its properties.

land utilization index (LUI). The number of days during which crops occupy the land during a year, divided by 365.

land water requirement. The net seepage and percolation requirement of the soil.

landholdings. Land owned or occupied or used by farmers or tenant farmers.

larva. The immature, wingless, and often vermiform (wormlike) feeding form that hatches from the egg of many insects, alters chiefly in size while passing through several molts, and is finally transformed into a pupa or chrysalis from which the adult emerges.

laser leveling. Land leveling technique wherein the leveling device, normally tractor-drawn, is controlled by a laser beam set at a certain bench mark or level.

latent infection. The state in which a host is infected with a pathogen but does not show any symptoms.

latent period. 1). In epidemiology, latent period refers to the time elapsed from arrival of a dispersal unit at a susceptible plant surface until the formation of the next generation of dispersal units. 2). Incubation period of a virus in an insect. The time between acquisition of the virus and the time when it becomes infective.

latent. Something, e.g., a gene or disease that is present in a plant but is unexpressed.

lateral. On the side.

latin square design. Experimental design used when there are two sources of variation among experimental units, as in the presence of a bidirectional fertility gradient in field experiments.

lattice designs. Incomplete block designs used in single-factor experiments having a large number of treatments.

lattice energy. The energy required to separate the ions of a crystal to an infinite distance from each other.

lax panicle. A panicle that is loose or open with a few lateral branches and sparsely distributed spikelets.

layout. Plan showing the allocation of treatments among experimental units. A detailed plan showing the arrangement of replications and treatments in an experiment.

lazy (la). Plants grow prostrate rather than upright because of an ageotropic growth habit. In rice literature, some extreme spreading forms have been mis-termed lazy.

LD50 (lethal dosage). The dose that is lethal to 50% of the test animals or micro organisms in a given time period. It is usually expressed in milligrams of insecticides per kilogram of body weight in mammals, and micrograms of insecticides per gram of body weight in insects. The lower the LD value, the higher the toxicity.

leaching. The removal or loss of nutrient elements in soil solution due to the downward movement of water.

leaf. An outgrowth from the stem of a vascular plant, usually green. It consists of a leaf-base, petiole and flattened lamina, which is usually conspicuously veined.

leaf angle. The angle of the leaf blade from the stem. The descriptive terms often used are erect (angle of 0-30 o), intermediate (31-60 o), horizontal (61-90 o), and descending (more than 90 o). The angle of the flag leaf on the rice plant is important in photosynthesis.

leaf area index. The sum of the leaf area of all green leaves divided by the ground area above which the leaves were growing.

leaf blade. The thin, elongated, flat portion of the leaf.

leaf blast. A rice disease caused by the fungus Pyricularia oryzae. Symptoms consist of elliptical spots with pointed ends, with gray or whitish center, and with brown or reddish brown margin.

leaf curling or rolling. Rolling of the leaves to control water loss affected by lack of atmospheric or soil moisture. Also the bending or twisting of the leaves due to viral disease (as in rice ragged stunt) or to other harmful agents.

leaf mesophyll cells. Cells within a leaf that produce carbohydrates in photosynthesis.

leaf scald. A rice disease caused by the fungus Gerlachia oryzae with symptoms consisting of zonate lesions starting from leaf tips or edges; the symptoms are usually observed in mature leaves.

leaf scraping. The removal of the epidermal portion of a leaf by the feeding of an insect.

leaf senescence. Change in color from green to yellow or brown due to a reduction of metabolic activities in the plant preceding the death of the plant. Natural drying of the leaves due to crop maturity.

leaf sheath. The lower part of the leaf enclosing the stem, originating from a node and wrapping around the culm above the node.

leaf veins. The vascular bundles of the leaf. In monocotyledonous plants such as rice, leaf veins are seen as longitudinal ridges.

leaffolder. The insect Cnaphalocrocis medinalis which causes damage by making a leafy tube and feeds within the tube consuming the leaf tissues except the epidermis.

leafhopper. Insect of the order Homoptera, family Cicadellidae, which feeds by sucking sap from leaf veins of the rice plant. They have more slender bodies and move more quickly than planthoppers.

leaflet. A segment of a compound leaf.

leghemoglobin. An iron-containing, red pigment produced in root nodules during the symbiotic association between Rhizobium and leguminous plants.

legume. Plant belonging to the family Leguminosae. Most legumes form a symbiosis with nitrogen-fixing rhizobia bacteria in specialized nodule structures that fix nitrogen.

lemma (syn. outer glume). One of the two bracts enclosing the flower or spikelet of rice. It becomes the covering of two-thirds of the rice seed surface and has five vertical ridges, formed along the surface, from the vascular bundles.

lepidoptera. An order of insects with two pairs of scaly wings and spirally coiled haustellate (formed for sucking) mouth structure, which undergoes complete metamorphosis. The larva has a chewing type of mouth parts and is always pestiferous.

lepidopterous. Pertaining to the insects in the order Lepidoptera.

lesion. A localized spot of diseased tissue on a plant.

lethal gene. A gene whose effect is sufficiently drastic to kill the bearer of certain genotypes.

levee (also called bund or dike). An embankment of soil for retaining water inside the ricefield. A dike made of soil to retain water in rice fields.

level. A flat surface of a ricefield, a horizontal line, or an index of altitude.

leveling. Land preparation involving moving soil from high to low spots in the field to achieve a flat horizontal surface so that irrigation water will be evenly distributed throughout the field.

library (biotechnology). A collection of cloned DNA fragments.

life cycle. The stages in the growth and development of an organism that occur between the appearance of the individual and its reproduction or death.

ligation. Joining of DNA fragments to produce a single DNA molecule. Ligases are enzymes which perform this reaction. Fragments of plant DNA are ligated into bacterial plasmids during the cloning of probes for use for RFLP analysis.

light soil. A coarse-textured soil such as sandy soil.

light transmission ratio. Light intensity at the ground level of a population divided by the light intensity at the top of the population.

light trap. A device for collecting insects, consisting of a light source which attracts insects at night and a mechanism that traps the insects.

ligule. A thin, upright, membranous appendage at the top of the leaf sheath. It is attached to the base on the inside of the leaf collar of the rice plant and some grasses.

liguleless (lg). Said of leaves that lack collar, ligule, and auricles; synonymous with juncturaless. The blade stands upright at base.

lime. A compound containing carbonates, oxides and/or hydroxides or calcium and/or magnesium used to neutralize soil acidity.

line. In plant breeding, plants originating from common parents or a common cross that is undergoing selection or improvement and which may become identified as a variety.

linear. Long and narrow with nearly parallel edges.

linear regression. A type of statistical analysis where a straight line or linear relationship characterizes the amount of change in a dependent variable which is associated with a unit change in the independent variable.

line breeding. A system of breeding in which a number of genotypes which have been progeny-tested with respect to some character or group of characters are composited to form a variety.

line sowing. To sow the seed in lines with a drill or by hand.

linkage. The association between two or more genes located on the same chromosome that tend to be inherited together.

linkage group. A set of genes that assort together and that assort independently of other genes.

linkage map. A scale representation of a chromosome that shows the relative positions of all its known genes or DNA sequences.

lister planting. A method of planting in which the seed is planted in the bottom of lister furrows, usually simultaneously with the opening of these furrows. A lister is a type of plow.

listing (middlebreaking). A tillage and land-forming operation using a tool which turns two furrows laterally in opposite directions, thereby producing beds or ridges.

liter. Unit of volume in the metric system equal to 1000 ml or 1000 cc.

literature. The body (accumulation) of written work produced by scholars or researchers in a given field.

lithao. A Philippine farm implement used for making small parallel furrows.

lobed. Partially divided into usually rounded or obtuse segments but not deeply enough to form separate entities.

local check or control. Farmer's variety or method. Used in experiments as a check in a specific place or community, in rice production.

locule. A cell.

locus. The position of a gene on a chromosome.

lodge, lodging. The falling down of rice plants in the field due to wind, rain, flooding, pest damage, or because the stems are too tall or too weak to stand erect during the grain-filling stage, usually causing yield loss.

lodicules. The two scalelike structures adjoining to the base of the palea which control the opening of the lemma and palea during anthesis.

long glume (g). The sterile lemmas ("outer glumes") exceed one-third the length of the lemma and palea. Another dominant gene, Gm, controls the sterile lemmas which are longer than the lemma and palea. The two sterile lemmas may have unequal length.

long smut. A common name for Tolyposporium erhenbergii.

long-duration varieties. Varieties that mature in 150 days or more.

long-term conservation. Long-term storage for maintenance of viability and purity of germplasm for up to 25 years for annual crops.

long twisted kernel (tk). A long caryopsis with a slight twist in the middle portion.

loose. 1). An uncompacted soil. 2). Spreading panicles.

loose smut. A fungal disease.

loosen, loosening. To break up, to not be compacted. Decreasing soil bulk density and increasing porosity due to the application of mechanical forces to the soil.

lowland field. A land area surrounded with dikes or levees to impound rain or irrigated water. An irrigated field surrounded by levees.

lowland rice. Rice grown on fields where water is held by bunds. About 30% of the world's rice is grown as rainfed lowland; about 45% as irrigated lowland. Some areas are flooded lowlands.

lowland vs upland soils. Terms commonly used in connection with rice culture to denote flooded (paddy) vs unflooded conditions.

lutescent (lu). Said of seedlings that are normally green at first, but in which the chlorophyll gradually disappears and the plant ultimately dies.

luxury uptake. The absorption by plants of nutrients in excess of their need for growth.

lysine. An essential amino acid in seed protein.