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Module 14 in the Syllabus

Plants Images
Image gallery for study with links to larger teaching JPEGs for classroom presentation

Question Drill for Plants
Conceptual Vocabulary Self-Test

Basic Terms Crossword Puzzle

Basic Puzzle Solution

Though it may be useful, detailed knowledge of plant biology is not required for the MCAT
Basic Terms

LeafA leaf is an above-ground plant organ specialized for photosynthesis.
ChlorophyllChlorophyll is a green pigment found in most plants, algae, and cyanobacteria which absorbs light to begin the energy transduction processes of photosynthesis.
Plant stemA main structural axes of a vascular plant, a stem is normally divided into nodes and internodes, the nodes holding buds and the internodes acting as spaces that distance one node from another.
RootIn vascular plants, the root is the organ of a plant body that typically lies below the surface of the soil
FlowerA flower, also known as a bloom or blossom, is the reproductive structure found in angiosperms.
Alternation of generationsAlternation of generations is a reproductive cycle of certain plants, fungi, and protists.
XylemXylem is one of the two types of transport tissue in vascular plants, phloem being the other one.
TranspirationTranspiration is the evaporation of water from the aerial parts of plants, especially leaves but also stems, flowers and roots.
SeedA seed is a small embryonic plant enclosed in a covering, usually with some stored food.
PollenPollen is a fine to coarse powder consisting of microgametophytes, the grains, which produce the male gametes of seed plants.
Flowering plantThe flowering plants or angiosperms are the most widespread group of land plants.
PetalA petal, regarded as a highly modified leaf, is one member or part of the corolla of a flower.
PhloemPhloem is the living tissue that carries organic nutrients in vascular plants, particularly sucrose, a sugar, to all parts of the plant where needed.
MeristemA meristem is a tissue in all plants consisting of undifferentiated cells and found in zones of the plant where growth can take place.
BudA bud is an undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of the stem.
FruitA fruit is the ripened ovary and sometimes surrounding tissues, together with seeds, of a flowering plant.
GametophyteA gametophyte is the structure, or phase of life in plants that undergo alternation of generations which contains only half of the total complement of chromosomes:
SporophyteAll land plants have life cycles in which a haploid gametophyte generation alternates with a diploid sporophyte.
Vascular plantThe vascular plants are those plants that have lignified tissues for conducting water, minerals, and photosynthetic products through the plant, also known as traeophytes or higher plants.
GymnospermThe gymnosperms are a group of spermatophyte seed-bearing plants with ovules on the edge or blade of an open sporophyll, the sporophylls usually arranged in cone-like structures.
CotyledonA cotyledon is a significant part of the embryo within the seed of a plant, which upon germination, becomes the embryonic first leaves of a seedling.
EndospermEndosperm is the albumen tissue produced in the seeds of most flowering plants around the time of fertilization. It surrounds the embryo and provides nutrition.
Apical dominanceApical dominance is the phenomenon whereby a main stem of the plant grows more strongly than other side stems.
BarkBark is the outermost layer of stems and roots of woody plants such as trees, which consists of three sublayers, the cork, the phloem, and the vascular cambium.
GerminationGermination is the process whereby growth emerges from a period of dormancy. The most common example is the sprouting of a seedling from a seed of an angiosperm or gymnosperm.
Root pressureRoot pressure occurs in the xylem of some vascular plants when the soil moisture level is high either at night or when transpiration is low during the day.
StomaA stoma is a tiny opening or pore, found mostly on the underside of a plant leaf, and used for gas exchange.
EmbryoAn embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination.
Conifer coneA cone is an organ on plants in the division Pinophyta that contains the reproductive structures.
SepalSepals are a part of the flower of angiosperms or flower plants. They are green and lie under the more conspicuous petals.
StamenThe stamen is the male organ of a flower which generally has a stalk called the filament, and, on top of the filament, an anther with pollen sacs, called microsporangia.
PetioleThe petiole is the small stalk attaching the leaf blade to the stem.
TrichomeTrichomes are fine outgrowths or appendages on plants and protists of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae.
Abscisic acidAbscisic acid is a plant hormone that functions in many plant developmental processes, including abscission and bud dormancy.
Palisade cellPalisade cells are a type of leaf tissue containing chloroplasts found within the mesophyll in leaves of dicotyledonous plants.
AuxinThe auxins are plant growth substances such as indole-3-acetic acid which play an essential role in coordination of many growth and behavioral processes in the plant life cycle.
Vascular cambiumThe vascular cambium is a lateral meristem, the source of both the secondary xylem (inwards, towards the pith) and the secondary phloem (outwards).
Compound fruitA compound fruit is one that develops from several ovaries in either a single flower or multiple flowers. Conversely, a simple fruit develops from one ovary.
SeedlingA seedling is a young plant sporophyte developing out of a plant embryo from a seed.
SpermatophyteThe spermatophytes comprise those plants that produce seeds.
CarpelA carpel, consisting of stigma, style, and ovary, is the outer, often visible part of the female reproductive organ of a flower; the basic unit of the gynoecium.
StipuleThe term stipule refers to outgrowths borne on either side of the base of a leafstalk or petiole.
Ground tissueThe types of ground tissue found in plants develop from ground tissue meristem and consists of three simple tissues: parenchyma, collenchyma, and sclerenchyma.
EpidermisThe epidermis is the outer single-layered group of cells covering a plant, especially the leaf and young tissues of a vascular plant including stems and roots.
Cork cambiumCork cambium is a tissue found in many vascular plants as part of the periderm. A lateral meristem, this tissue is responsible for secondary growth replacing epidermis in roots and stems.

Intermediate Terms

GibberellinGibberellins (GAs) are plant hormones involved in promotion of stem elongation, mobilization of food reserves in seeds and other processes.
ApomixisApomixis refers asexual reproduction in plants, without fertilization.
FernFerns are vascular plants differing from the more primitive lycophytes by having true leaves (megaphylls) and from seed plants (gymnosperms and angiosperms) in their mode of reproduction, lacking flowers and seeds.
OvuleIn seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells.
RadicleThe radicle is the first part of a seedling to emerge from the seed during the process of germination.
AerenchymaAerenchyma is an airy tissue found in roots of plants, which allows exchange of gases between the shoot and the root.
PlasmodesmataPlasmodesmata are microscopic channels of plants traversing the cell walls and middle lamella between pairs of plant cells and facilitating transport and communication between them.
BulbA bulb is an underground vertical shoot that has modified leaves used as food storage organs by a dormant plant.
Multiple fruitMultiple fruits are fruits that are formed from a cluster of flowers growing on a catkin.
CytokininCytokinins (CK) are a class of plant hormones active in promoting cell division, and are also involved in cell growth, differentiation, and other physiological processes.
PithPith is a light substance that is found in vascular plants consisting of soft, spongy parenchyma cells in the center of the stem.
TaprootA plant's taproot is a straight tapering root that grows vertically down, forming a center from which other roots sprout.
HypocotylThe hypocotyle is the primary organ of extension of the young seed plant and develops into the stem.
Red algaeThe red algae (Rhodophyta) are a large group, about 5000-6000 species of mostly multicellular, marine algae, including many notable seaweeds.
EmbryophyteThe embryophytes are the most familiar group of plants including trees, flowers, ferns, mosses, and various other green land plants, complex multicellular eukaryotes with specialized reproductive organs.
BryophyteThe bryophytes are those embryophytes that are non-vascular.
RhizoidIn land plants, rhizoids are trichomes that anchor the plant to the ground. In vascular plants they are often called root hairs, and may be unicellular or multicellular.
HornwortHornworts are a group of bryophytes, or non-vascular plants, comprising the division Anthocerotophyta. The common name refers to the elongated horn-like structure, which is the sporophyte.

Advanced Terminology

RhizomeA rhizome is a horizontal main stem of a plant that is usually found underground and often sends out roots and shoots from its nodes.
StolonStolons are horizontal stems which grow at the soil surface or below ground, they form new plants at the ends or at the nodes.
SporophyllA sporophyll is a leaf that produces spores.
AntheridiumAn antheridium is a haploid structure or organ producing and containing male gametes, which is present in the gametophyte phase of lower plants like mosses and ferns, and also in the primitive vascular psilotophytes.
ArchegoniumAn archegonium is a structure of the gametophyte phase of certain plants producing and containing the ovum. The term is not used for angiosperms where the megagametophyte is reduced to just a few cells.
StrobilusA strobilus is an organ of many plants that contains the reproductive structures, ordinarily called cones in many of these groups.
InflorescenceAn inflorescence is a group or cluster of flowers arranged on a stem that can have only one main branch or be composed of complicated arrangements of branches.
CormA corm is a short, vertical, swollen underground plant stem that serves as a storage organ used by some plants to survive winter or other adverse conditions such as summer drought and heat.
PericycleThe pericycle is a cylinder of parenchyma cells that does not allow water and nutrients coming from the soil to enter the vascular bundles apoplastically
PericarpThe pericarp is the tissue surrounding a seed that develops from the ovary wall of the flower. It is the fruit making body in many types of fruits including nuts.
StenospermocarpyStenospermocarpy is the biological mechanism that produces seedlessness in some fruits, notably many table grapes.
EndodermisThe endodermis is a thin layer of parenchyma found in roots, just outside the vascular cylinder.
Casparian stripThe Casparian strip is a band of wall material in the radial and transverse walls of the endodermis used to block the passive flow of materials, such as water and solutes into the stele of a plant.
GravitropismGravitropism [or geotropism] is a turning or growth movement by a plant or fungus in response to gravity.
ChlorophytaChlorophyta, a division of green algae related to the Charophyta and Embryophyta (land plants) includes about 8000 species of mostly aquatic photosynthetic eukaryotic organisms.
CharalesThe Charales are an order of green alga believed to be the closest relatives of the green land plants.
ProtonemaA protonema is a thread-like chain of cells that forms the earliest stage (the haploid phase) of a bryophyte life cycle.
HydathodeA hydathode is a type of tissue in the leaves of certain plant species that permits the release of water through pores in the epidermis or margin of leaves.
GuttationGuttation is the appearance of drops of xylem sap on the tips or edges of leaves of some vascular plants, such as grasses.
LycopodiophytaThe division Lycopodiophyta is the oldest extant vascular plant division at around 420 million years old, and includes some of the most primitive extant species.
MicrophyllMicrophyll refers to the leaves of the Lycopodiophyta which have only a single, unbranched vascular trace.
PteridophyteConsisting of several groups including mosses, ferns and horsetails, the pteridophytes are vascular plants that neither flower nor produce seeds.
ProthalliumThe term prothallium is used to describe the gametophyte stage of many spore-bearing plants.
CycadCycads are a group of seed plants characterized by a large crown of compound leaves and a stout trunk which are frequently confused with palms or ferns, but are related to neither.
TepalTepals are elements of the perianth, or outer part of a flower. The term is usually used when all segments of the perianth, the petals and sepals, are of similar shape and color, or undifferentiated
CladophyllCladophylls, also called cladodes, are photosynthetic branches or portions of a stem that resemble and function as a leaf, as in the asparagus.
Unifacial cambiumThe unifacial cambium is a cylindrical laterel meristem involved in secondary growth in the stems of some extinct lycophytes and equisetophytes.
Bast fibreBast fiber or skin fiber is fiber collected from the phloem or bast surrounding the stem of certain mainly dicotyledonic plants, such as flax or hemp.
ParthenocarpyParthenocarpy is the natural or artificially induced production of fruit without fertilization of ovules.
KinetinKinetin is a chemical analogue of cytokinins, a class of plant hormone that promotes cell division.
SuberinSuberin is a waxy substance found in higher plants that is a main constituent of cork.
ColeoptileColeoptile is the pointed protective sheath covering the emerging shoot in monocotyledons such as oats and grasses.
EpicotylThe epicotyl is the embryonic shoot above the cotyledons.

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