ab.sorb transitive verb /əb zorb/

to take in or soak up.

a.chene noun /eI kin/

a small, dry, hard seed that is attached at a single point and that does not split open when it is mature.

ac.tive tran.sport noun

the movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring an expenditure of energy.

ad.sorb transitive verb /əd sorb or əd zorb/

to gather (a gas or liquid) to a surface.

aer.o.bic adjective /eI ro bihk/

occurring or living only in the presence of oxygen.

al.lele nounlil/

one of two or more versions of a gene. An individual inherits two alleles for each gene, one from each parent. If the two alleles are the same, the individual is homozygous for that gene. If the alleles are different, the individual is heterozygous.

al.log.a.my nounla gə mi/

the process of cross-fertilization in plants. (Cf. autogamy.)

an.gi.o.sperm noun /aen ji ə spərm/

a flowering plant that holds its seeds within an ovary.

an.i.on noun /aen aI ən/

a negatively charged ion. (Cf. cation.)

an.ther noun /aen thər/

the part of a flower’s stamen that bears pollen.

Ar.chae.a noun /ahr kee uh/

one of the three-domain system (the other are Bacteria and Eucarya) which includes halophiles (inhabit extremely salty environments), methanogens (produce methane), and thermophiles (thrive extremely hot environments).

A.T.P noun /eI ti pi/

a biochemical compound that serves to store energy in all living cells; adenosine triphosphate.

au.tog.a.my noun /o ta gə mi/

in botany, self-fertilization, as of a flower with its own pollen. (Cf. allogamy.)

aux.in noun /awk sən/

any of a group of organic compounds, often plant hormones, that affect plant growth.

ax.il noun /aek sihl/

the upper angle between a leaf, flower, twig, or the like, and the stem or branch from which it grows.

Bac.te.ri.a noun /baek ti ri ə/

one of the three-domain system (the other are Archaea and Eucarya). Bacteria are one-celled microscopic organisms of various shapes that are often agents of fermentation and putrefaction and that, in some cases, cause disease.

boun.dar.y lay.er

the layer of fluid closest to the surface of a solid past which the fluid flows: it has a lower rate of flow than the bulk of the fluid because of its adhesion to the solid.

bract noun /braekt/

a leaflike part usually located below a flower or flower cluster.

C3 Car.bon Fix.a.tion

C3 carbon fixation is one of three biochemical mechanisms, along with C4 and CAM photosynthesis, used in carbon fixation. It is named for the 3-carbon molecule present in the first product of carbon fixation in the large subset of plants known as C3 plants, in contrast to the 4-carbon molecule products in C4 plants

C4 Car.bon Fix.a.tion

C4 carbon fixation is one of three biochemical mechanisms, along with C3 and CAM photosynthesis, used in carbon fixation. It is named for the 4-carbon molecule present in the first product of carbon fixation in the small subset of plants known as C4 plants, in contrast to the 3-carbon molecule products in C3 plants

Cal.vin Cy.cle noun

a cycle of biochemical reactions taking place in the chloroplasts of plants during photosynthesis, in which carbon dioxide is fixed and six-carbon sugar is formed; also called Calvin-Benson cycle. Named for Melvin Calvin, Nobel prize-winning chemist.

ca.lyx noun /keI lihks or kae lihks/

(calyces, calyxes) the outermost part of a flower, composed of usually green sepals.

can.de.la noun /kaen del ə/

the basic unit of intensity of light, equal to one sixtieth of the intensity of one square centimeter of a radiating body at the temperature of solidification of platinum.

can.dle.pow.er noun /kaen dəl paU ər/

an obsolete unit expressing luminous intensity, equal to 0.981 candela. Originally defined in England by the Metropolitan Gas Act 1860 as the light produced by a pure spermaceti candle weighing one sixth of a pound and burning at a rate of 120 grains per hour.

can.o.py noun /kae nə pi/

the overarching, rooflike cover of upper foliage in a forest or planting.

capitate adjective /kae pə teIt/

ending in a distinct compact head.

car.pel noun /kar pəl/

the female organ of a flower, consisting of a modified leaf that forms a single pistil or one member of a compound pistil, in which the seeds mature.

cat.i.on noun /kae ti ən or kae ti an/

an ion with a positive charge. (Cf. anion.)

cell noun /sel/

a microscopic unit of plant or animal life, usually containing a nucleus and surrounded by a very thin membrane.

cel.lu.lose noun /sel yə los/

an inert carbohydrate that is the main element of plant tissue.

chem.o.type noun /ki mo taIp/

a chemically distinct entity in a plant or microorganism.

chlo.ro.phyll noun /klo rə fIl/

the green pigment in the leaves and stems of plants that is necessary for the production of plant food by photosynthesis.

chlo.ro.plast noun /klo rə plaest/

a small oval green bit of protoplasm that contains chlorophyll and is the location of photosynthesis.

chro.mo.some noun /kro mə som/

one of the tiny, threadlike, DNA-containing bodies found in the cell nuclei of all plants and animals, responsible for transmitting hereditary characteristics.

cir.ca.di.an adjective /sər keI di ən/

denoting or concerning behavioral or physiological activities that recur at about twenty-four-hour intervals, such as sleep rhythms.

clay noun /kleI/

earth that consists mainly of hydrated silicates of aluminum, the constituent particles of which are less than 0.002 mm in diameter.

clone noun /klon/

an organism produced asexually from a single ancestor and genetically replicating it.

Co.he.sion-Ten.sion mech.a.nism

col.loid noun /ka loId/

in chemistry, a suspension of a very finely ground or divided substance in a gas, liquid, or solid, such that suspended particles tend not to settle out.

con.cen.trate noun /kan sən treIt/

something in concentrated form, such as juice or flavoring. (verb) To make or become denser or purer by the removal of certain elements, especially the solvent of a solution.

con.vec.tion noun /kən vek shən/

the motion or transmittal of heat through a liquid or gas because of the natural rising of the heated parts and sinking of the cooled parts.

cor.tex noun /kor teks/(cortexes, cortices)

the outermost layer of the stem or root of a plant, bounded on the outside by the epidermis and on the inside by the endodermis.

Crass.u.la.cean Ac.id Me.tab.o.lism (CAM) noun /kraes ə leI shən/

a type of photosynthesis exhibited by many succulent plants in which carbon dioxide is taken up and stored during the night to allow the stomata to remain closed during the daytime, thus decreasing water loss.

cu.ti.cle noun /kyu tih kəl/

the outer, waxy layer of the leaf. This layer’s primary function is to prevent water loss within the leaf.

cyst.o.lith noun /sIst ə lIth/

a mineral concretion, usually of calcium carbonate, occurring in the epidermal cells of certain plants.

dark re.ac.tions noun

the second stage of photosynthesis (also called the the Calvin Cycle) that does not require the presence of light. It involves the fixation of carbon dioxide and its reduction to carbohydrate and the dissociation of water, using chemical energy stored in ATP.

der.mal tis.sue noun /duhr məl tI shu/

Also called the epidermis, this is the tissue of a plant other than the ground, and vascular tissues. The outer protective layer of the primary plant body (the roots, stems, leaves, flowers, fruits, and seeds). The epidermis is usually one cell layer thick, and its cells lack chloroplasts.

di.cot.y.le.don noun /daI kali dən/

a member of a large group of flowering plants that bear two embryonic seed leaves at sprouting, such as oaks, beans, and cabbages. (Cf. monocotyledon.)

dif.fu.sion noun /dih fyu zhən/

a mixing of molecules of different substances, that results from random thermal motion.

di.lute transitive verb /dih lut or daI lut/

to make (a solution) thinner or less concentrated by adding more solvent.

adjective Decreased in concentration or strength, especially as a result of adding something else; diluted.

di.oe.cious adjective /daI i shəs/

especially of plants, having the male and female reproductive organs in separate individuals.

do.lo.mite noun /domaIt/

a sedimentary rock, similar to limestone, that consists mainly of this mineral.

dom.i.nant adjective /dam ə nənt/

in genetics, of a gene or trait that masks the influence of a recessive when the two appear together. (Cf. recessive.)

e.da.phic adjective /ih daf ik/

of, produced by, or influenced by the soil.

e.lec.tron noun /ih lek tran/

a negatively charged particle, considered a fundamental unit of matter, that exists independently or outside the nucleus of an atom.

en.do.der.mis noun /en də dərməs or en do dərməs/

an inner layer of cells in the cortex of a root and of some stems, surrounding a vascular bundle.

en.dog.e.nous adjective /en da jə nihs/

  1. coming or produced from or developing within, as certain spores, or due to internal conditions, as certain diseases. (Cf. exogenous.)
  2. of, pertaining to, or constituting the metabolism of elements of living tissue containing nitrogen.

ep.i.der.mis noun /eduhr mihs/

in many plants and other organisms, an outer protective layer of cells.

e.rect.o.phile adjective /ih rekt ə faIl/

predominantly vertical arrangement of leafs in a plant or crop.


plant characterized as such. (Cf. planophile.)

e.ti.o.late transitive verb /i ti ə leIt/

to keep (a plant or the like) a light color by preventing exposure to sunlight; blanch; bleach.

intransitive verb to whiten or lose color, as a plant lacking sunlight.

eu.di.cots noun /yoo də katz/

an angiosperm having two cotyledons in the seed; they are the largest group of flowering plants.

Eu.car.y.a noun /yoo kar ee uh/

one of the three-domain system (the other are Bacteria and Eucarya). A domain of organisms having cells each with a distinct nucleus within which the genetic material is contained.

ex.og.e.nous adjective /ek sa jə nihs/

  1. having external causes or origins. (Cf. endogenous.)
  2. in botany, of or pertaining to a process of growing in diameter by addition of successive layers under the bark; cambial.

fert.i.ga.tion verb /fuhr tih geI shən/

the application of fertilizers, soil amendments, or other water-soluble products through an irrigation system.

fil.a.ment noun /fI lə mənt/

a threadlike structure, stalk that connects to and holds up the anther.

fil.i.al adjective /fI li əl/

denoting the generation or generations after the parental generation.

flac.cid adjective /flae sihd/

without firmness; soft; flabby. (Cf. turgid.)

flor.i.gen noun /flo rih gen/

the protein responsible for controlling and/or triggering flowering in plants. Florigen is produced in the leaves, and acts in the shoot apical meristem of buds and growing tips.

flow.er noun /flaU ər/

the seed-bearing part of a plant, consisting of reproductive organs (stamens and carpels) that are typically surrounded by a brightly colored corolla (petals) and a green calyx (sepals)

flush noun /fluhsh/

a brief but heavy gush or flow, especially of water. transitive verb to wash out, clean, or empty with a swift gush or flow of water.

flux noun /fluhks/

in physics, the rate of flow of matter or energy considered as a fluid.

foot-can.dle (foot candle) noun /fUt kaen dəl/

a unit of illumination equal to that produced by one candela at a distance of one foot, or to one lumen per square foot.

gam.ete noun /gae mit/

a mature reproductive cell, such as an egg or sperm, that is capable of uniting with another cell to form a new organism.

gene noun /jin/

a section of a chromosome that determines the structure of a single protein or part of one, thereby influencing a particular hereditary characteristic, such as eye color, or a particular biochemical reaction.

gen.o.type noun /jetaIp/

  1. the genetic makeup of a living creature. (Cf. phenotype.)
  2. a collection of living creatures with the same genetic makeup.

gla.brous adjective /glae brəs/

having no hair or fuzz; bald; smooth.

glu.cose noun /glu kos/

a form of sugar that occurs naturally in fruits, plants, and animal tissues; grape sugar.

ground tis.sue noun /graUnd tI shu/

The tissue of a plant other than the epidermis, and vascular tissues.

guard cell noun /gard sel/

each of a pair of curved cells that surround a stoma, becoming larger or smaller according to the pressure within the cells.

gyp.sum noun /jIp səm/

a mineral, hydrated calcium sulfate, that resembles chalk and is used to make plaster of Paris, plaster and wallboard, and fertilizers.

he.red.i.ty noun /hə re dih ti/

  1. the genetic transmission of traits or tendencies from parent to offspring.
  2. the collective traits or tendencies inherited in such a way.

her.maph.ro.dite noun /hər mae frə daIt/

  1. an individual with both male and female reproductive organs.
  2. an organism, such as an earthworm or plant, that characteristically possesses both male and female reproductive organs.

het.er.o.zy.gous adjective /he tə rə zahy guhs or he tə ro zahy guhs/

having two different alleles at corresponding positions on homologous chromosomes.

ho.mo.zy.gous adjective /hoh muh zahy guhs or hoh mo zahy guhs/

having the same alleles at corresponding positions on homologous chromosomes.

hu.mus noun /hyu məs/

a dark organic material, composed of partly decayed leaves and plants, that adds nutrients and water-retaining ability to soil.

hy.brid noun /haI brihd/

the offspring of two plants or animals that differ genetically as to species, variety, breed, or the like.


produced by cross-breeding.

hy.per.ton.ic adjective /haI pər ta nihk/

having a higher osmotic pressure than a particular fluid, typically a body fluid or intracellular fluid.

hy.po.ton.ic adjective /haI pər ta nihk/

having a lower osmotic pressure than a particular fluid, typically a body fluid or intracellular fluid.

il.lu.mi.nance noun /ih lu mə nəns/

the intensity of light per unit of area on a surface exposed to light; illumination.

in-vitro adjective, adverb /in vi tro/

(of processes or reactions) taking place in a test tube, culture dish, or elsewhere outside a living organism.

in-vivo adjective, adverb /in vi vo/

(of processes) taking place in a living organism.

in.flo.res.cence noun /In flə re səns/

a cluster of flowers or a single flower on a plant.

in.or.gan.ic adjective /In or gae nihk/

of a chemical substance, not containing carbon.

i.on noun /aI an or aI ən/

an atom, group of atoms, or molecule that bears a positive electric charge as a result of electron loss or a negative charge as a result of electron gain.

ir.ra.di.ance noun /ih rey dee uhns/

the radiant flux incident on unit area of a surface (normal to the direction of flow of radiant energy through a medium). It is measured in watts per square metre (W/m²).

i.so.mer noun /aI sə mər/

a chemical compound that has the same kind and number of atoms as one or more other compounds, but differs from them in structural or spatial arrangement of the atoms and therefore in its properties.

i.so.ton.ic adjective /aIta nihk/

  1. equal in tension.
  2. of or showing equal osmotic pressure.

la.bile adjective /leI baIl or leI bihl/

  1. subject to or ready for change; adaptable.
  2. unstable, as chemical elements or compounds.

leaf.let noun /lif liht/

any of the segments or blades that form a compound leaf.

L.E.D abbreviation /el i di/

abbreviation of “light-emitting diode,” a semiconductor diode that emits light when electrified, used for displaying readings on electronic watches, calculators, and the like.

light re.ac.tions noun

the first stage of photosynthesis during which energy from light is used for the production of ATP.

lu.men noun /lu mən/

(lumens, lumina)

a unit of measure of the flow of light, equal to the flow from a light source of one-candle strength, measured on a unit surface at a unit distance. (abbr.: lm)

lu.mi.nance noun /lu mih nəns/

the measure of brightness of a light source or a luminous surface in candelas per unit area.

lu.mi.nous flux noun /lu mih nəs fluhks/

the measure of the rate at which perceived light flows through a given area.

lu.mi.nous flux density noun /lu mih nəs fluhks den sih ti/

a measure of the rate of flow of luminous energy per unit time, evaluated according to its ability to produce a visual sensation. The SI unit of measure for luminous flux density is the lumen (lm).

lu.mi.nous in.ten.si.ty noun /lu mih nəs ihn ten sih ti/

the quantity of visible light that is emitted in unit time per unit solid angle (steradian). The SI unit of luminous intensity is the candela (cd).

lux noun /luks/

(luces, luxes)

a unit of illumination equal to one lumen per square meter.

mei.o.sis noun /maI o sihs/

the process in which the diploid chromosomes of a cell are replicated once, followed by two divisions of the nucleus, to give rise to four haploid cells that may develop into gametes or spores.

mem.brane noun /mem breIn/

  1. a thin, flexible, tensile layer of tissue that separates, connects, lines, or covers various structures, such as organs, in living organisms.
  2. a bilayer of lipid molecules that serves as a covering for cells.

mer.i.stem noun /mae rih stem/

a region of plant tissue, found chiefly at the growing tips of roots and shoots and in the cambium, consisting of actively dividing cells forming new tissue.

mes.o.phyll noun /mez uh fil or mes uh fil/

the inner tissue of a leaf, containing many chloroplasts.

me.tab.o.lism noun /mə tae bə lih zəm/

the physical and chemical processes by which food is converted by a living organism to provide energy and produce and maintain cells and tissues.

mi.to.sis noun /maI to sihs/

  1. duplication and division of the nucleus of a dividing cell.
  2. cell division in which this process occurs.

mon.o.cot.y.le.don noun /makali dən/

a member of the subgroup of flowering plants that produce only one seed leaf, usually bear leaves with parallel veins, and do not grow in width by means of a vascular cambium. (Cf. dicotyledon.)

derived forms:

monocot (n.)

mo.noe.cious adjective /mə ni shəs/

in botany, having both male and female flowers on each individual plant.

mon.o.typ.ic adjective /matI pihk/

of a biological species, being the unique representative of one’s gender, family, or higher taxonomic classification.

node noun /nod/

a usually thickened part or joint of a plant stem, from which a leaf or bud may grow.

or.gan.ic adjective /or gae nihk/

of or pertaining to compounds that contain carbon. (Cf. inorganic.)

os.mo.sis noun /az mo sihs or as mo sihs/

the passage or diffusion of a liquid through a semipermeable membrane until the concentration is the same on both sides of the membrane, or the tendency of a liquid to diffuse in such a way.

outcross verb /aUt kraws/

breed (an animal or plant) with one not closely related.

an animal or plant produced as the result of outcrossing.

o.va.ry noun /o və ri/


in a flowering plant, the lower section of the pistil that contains the ovules or seeds and that enlarges to form the fruit.

pal.i.sade cell noun /pae lih seId sel/

plant cells found within the mesophyll in leaves of many plants, right below the upper epidermis and cuticle. They are vertically elongated, a different shape from spongy mesophyll cells beneath them in the leaf.

pen.du.lous adjective /pen jə ləs or pen də ləs or pend yə ləs/

hanging downward; suspended so as to swing or sway.

pet.al noun /pe təl/

one of the separate, modified leaves, usually of a different color from the plant’s other leaves, that form the outer part of a flower head.

pet.i.ole noun /pe ti ol/

the thin stalk by which a leaf is attached to a stem.

pH abbreviation /pi eIch/

a symbol for a measure of the degree of alkalinity or acidity of a solution, determined by the concentration or activity of hydrogen ions therein (often followed by a number, with seven indicating neutrality, zero to six indicating acidity, and eight to fourteen indicating alkalinity).

phe.nol noun /fi nawl or fi nal/

a poisonous white acidic compound found in the tars of wood and coal, or derived from benzene, and used primarily as a disinfectant or antiseptic.

phe.no.type noun /fitaIp/

  1. the observable traits of an individual or group, especially as a function of genetic composition and environment. (Cf. genotype.)
  2. an individual or group that exhibits these traits.

pher.o.mone noun /femon/

any of a group of chemical substances produced by a plant or animal to elicit a response or behavior from another of the same species.

phlo.em noun /flo əm/

the soft tissue in vascular plants that contains tubes and other cellular and fibrous material used to conduct food.

pho.tom.e.try noun /fo ta mih tri/

the measurement of light, especially its intensity or fluctuation.

pho.to.per.i.od noun /fo to pir i əd/

the period of time each day during which an organism receives illumination; daylength.

pho.to.re.vers.i.ble adjective /fo to rih vuhr sih bəl/

Describing any compound or system that can exist in two forms, and can be changed from one to the other by the appropriate influence of light.

pho.to.syn.the.sis noun /fo to sIn thə sihs/

the process in plants by which sunlight, with the help of chlorophyll, is converted to chemical energy that is used to synthesize inorganic compounds into organic ones, especially sugars.

Pho.to.syn.thet.ic Ac.tive Ra.di.a.tion (PAR)

the spectral range of solar radiation from 400 to 700 nanometers that photosynthetic organisms are able to use in the process of photosynthesis.

Pho.to.syn.thet.ic Pho.ton Flux Den.si.ty (PPFD)

the photon flux density of PAR, also referred to as Quantum Flux Density. This is the number of photons in the 400-700 nm waveband incident per unit time on a unit surface.

phyl.lo.tax.y noun /fItaek si/

  1. the arrangement of plant leaves along a stem, or the principles governing this arrangement.
  2. the study of these principles.

phy.to.chem.is.try noun /faI to ke mih stri/

the branch of chemistry that deals with plants and the substances they produce.

phy.to.chrome noun /fahy tuh krohm or fahy to krohm/

a blue-green pigment found in many plants, in which it regulates various developmental processes.

pig.ment noun /pIg mənt/

the natural coloring matter of animal or plant tissue (as in chlorophyll).

pis.til noun /pI stihl/

the organ of a flower that contains the ovule or ovules.

plan.o.phile adjective /plein ə faIl/

predominantly horizontal arrangement of leafs in a plant or crop.


plant characterized as such. (Cf. erectophile.)

plan.tae noun /plaen teI/

the taxonomic kingdom comprising all living or extinct plants

pol.len noun /pa lən/

the fine-grained powder that a flowering plant produces which, when transferred to another plant of the same species, fertilizes that plant’s seeds.

pol.y.morph noun /pol ee mawrf/

an organism or inorganic object or material that takes various forms.

pol.y.tip.ic adjective /pol ee tip ik/

Having several variant forms, especially containing more than one taxonomic category of the next lower rank.

prop.a.gate transitive verb /prageIt/

to reproduce (offspring) or cause to reproduce.

pro.tein noun /pro tin/

any of a group of complex organic compounds containing nitrogen and composed of chains of amino acids, found in all living organisms and considered essential to all animal life processes.

pro.ton noun /pro tan/

an elementary particle of matter in the nucleus of all atoms, having a positive electrical charge.

pu.bes.cent adjective /pyu be sənt/

covered with soft down or fine, short hairs.

pul.vin.us noun /puhl vahy nuhs or puhl vi nuhs/


an enlarged section at the base of a leaf stalk in some plants that is subject to changes of turgor, leading to movements of the leaf or leaflet.

ra.di.an noun /reI di ən/

a unit of angle, equal to an angle at the center of a circle whose arc is equal in length to the radius.

ra.di.ance noun /reI di əns/

the flux of radiation emitted per unit solid angle (steradian) in a given direction by a unit area of a source.

ra.di.ant flux noun /reI di ənt fluhks/

the rate at which radiant energy such as heat or light flows through a given area.

ra.di.ant flux den.si.ty noun /reI di ənt fluhks den sih ti/

the radiant energy in a beam of electromagnetic, thermal, or acoustic radiation passing through a unit normal section per unit time. The SI units for these quantities are watts per square meter (W/m²). Also called irradiance.

ra.di.ant in.ten.si.ty noun /reI di ənt ihn ten sih ti/

in radiometry, a measure of the intensity of electromagnetic radiation. It is defined as power per unit solid angle. The SI unit of radiant intensity is watts per steradian (W. sr¹).

rad.i.om.e.try noun /reI di a mih tri/

in optics, a set of techniques for measuring electromagnetic radiation, including visible light.

re.cep.ta.cle noun /rih sep tə kəl/

the part of a flower stalk where the parts of the flower are attached.

re.ces.sive adjective /rih se sihv/

in genetics, of an allele or trait whose influence or characteristic does not appear when combined with a masking or dominant allele or trait. (Cf. dominant).


in genetics, a recessive allele or trait. (Cf. dominant).

root cap noun /rut kaep/

a protective cap of parenchyma cells that covers the terminal meristem in most root tips.

root hair noun /rut heIr/

a filamentous extension of an epidermal cell near the tip of a rootlet that functions in absorption of water and minerals.

ro.sal.es noun /ro zol əs/

an order of dicotyledonous plants having flowers with the petals separate or in some members of the family Leguminosae more or less united, a partly united calyx, epigynous or perigynous stamens, and one or more carpels

ro.sid noun /ro sid/

the rosids are members of a large monophyletic clade of flowering plants, containing about 70,000 species, more than a quarter of all angiosperms.

sand noun /saend/

loose grains of finely ground rock, often including quartz, the constituent particle of which are of a size between 2.0 mm and 0.05 mm in diameter

seed noun /sid/ (seed, seeds)

the small part of a flowering plant that is capable of growing into a new plant.

sel.fing transitive verb /self ing/ slang (See autogamy.)

se.pal noun /si pəl/

one of the leaflike parts that enclose an unopened flower.

ses.sile adjective /se sihl or se saIl/

  1. of a leaf or the like, attached at the base directly to the stem of the plant.
  2. unable to move freely; permanently fixed.

silt noun /sIlt/

fine sediment deposited by water, as of earth, clay, or sand, the constituent particles of which are between 0.05 mm and 0.002 mm in diameter.

sko.to.phile (scotophile) noun /skot ə faIl/

an organism that requires or has an affinity for darkness. (Cf. photophile.)

sol.ute noun /sal yut/

the substance that has been dissolved to form a solution.

so.lu.tion noun /sə lu shən/

a liquid mixture in which the minor component (the solute) is uniformly distributed within the major component (the solvent).

sol.vent adjective /sal vənt/

able to dissolve another substance.


a substance that is able to dissolve certain other substances.

sta.men noun /steI mən/

(stamens, stamina)

the stalklike part of a flower that produces and bears the pollen.

ste.le noun /sti li or stil/

(stelai, steles)

the central core of vascular tissue in plant stems and roots.

ste.ra.di.an noun /stuh rey dee uhn/


the SI unit of solid angle, equal to the angle at the center of a sphere subtended by a part of the surface equal in area to the square of the radius. (abbr.: sr)

stig.ma noun /stIg mə/

(stigmas, stigmata)

part of a plant that receives pollen; pistil.

stip.ule noun /stIp yul/

either of a pair of small, leaflike parts at the base of a leaf in plants such as the bean, pea, or rose.

sto.ma noun /sto mə/

(stomas, stomata)

any of various microscopic openings in the epidermis of a leaf or stem through which gases and water vapor are exchanged.

sto.mat.al con.duct.ance noun /kən dək təns/

usually measured in µmol m²s¹, is the measure of the rate of passage of carbon dioxide entering, or water vapor exiting through the stomata of a leaf.

style noun /stahyl/

(in a flower) a narrow, typically elongated extension of the ovary, bearing the stigma.

tax.on.o.my noun /taek sa nə mi/

in biology, the system of classifying plants and animals by grouping them into categories according to their similarities.

ter.pene noun /tuhr pin/

any of several unsaturated hydrocarbons, derived from resins and oils, that are used primarily in medicines and perfumes.

tran.spir.a.tion noun /tran spuh rey shun/

the process of water movement through a plant and its evaporation from aerial parts, such as from leaves but also from stems and flowers.

tri.chome noun /trik ohm/

a small hair or other outgrowth from the epidermis of a plant, typically unicellular and glandular.

tro.pism noun /tro pih zəm/

in biology, the turning or growth of an organ or organism toward or away from an external stimulus such as light, gravity, or nutrients.

tur.gid adjective /tuhr jihd/

swollen, as from a fluid or inner pressure.

vas.cu.lar tis.sue noun

the tissue in higher plants that constitutes the vascular system, consisting of phloem and xylem, by which water and nutrients are conducted throughout the plant.

watt noun /wat/

a unit of electrical power equal to the current of one ampere produced by the electromotive force of one volt, or to one joule per second. (abbr.: w, W)

xy.lem noun /zaI ləm/

a plant’s woody tissue that carries water and mineral salts.

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