acellular endosperm An unusual substance found in coconuts, known in the grocery store as “coconut water.” It consists of free nuclei floating in a nutritious cytoplasmic bath. As the coconut matures, cell walls form, and much of this material transforms into the meat (i.e., solid endosperm) of the coconut. (Some other seed endosperms pass through a brief acellular stage very early in their development, but only coconuts maintain it for so long and in such quantities.)
adenosine A compound with a wide range of vital functions in biochemistry. In the brain, it plays an important role in signaling fatigue and guiding the body toward sleep.
alkaloid Any of a large group of nitrogen-based compounds produced by plants and some marine organisms. They often function as chemical defenses, and many of them, including stimulants (e.g., caffeine), drugs (e.g., morphine), and poisons (e.g., strychnine), produce a strong reaction in people.
allele One of the possible forms of a gene, determined by differences in DNA and resulting in different expressions of that gene (e.g., wrinkled vs. smooth peas, or brown vs. red hair in people).
angiosperm A “flowering plant,” defined by having its seed enclosed in tissue to form a carpel (see carpel, below). The vast majority of living plants are angiosperms.
apomixis Asexual reproduction in plants that occurs when egg cells are produced with a full set of chromosomes, requiring no fertilization by pollen. The resulting seeds are essentially clone-like offspring of the parent. This strategy has evolved occasionally in a wide range of plant families, but is perhaps most common in the asters, including the dandelion, and the hawkweeds that so confounded Gregor Mendel.
caffeine An alkaloid found in a number of plants (notably coffee, tea, kola, and cacao) that helps deter attacks by insects and other pests, and may also function in the soil as an herbicide and germination inhibitor. Used by people as a stimulant.
carbohydrate A group of compounds in biochemistry composed of carbon, hydrogen, and oxygen atoms in various combinations. The results are generically called sugars, but they can be used for everything from energy storage in seeds (e.g., starch) to the exoskeleton of insects (called chitin).
Carboniferous The fifth Period of the Paleozoic Era, following the Devonian and lasting from 360 million to 286 million years ago (includes the Mississippian and Pennsylvanian sub-periods).
carpel The defining characteristic of the angiosperms that evolved from the leaves or bracts that surrounded and enclosed the seed, forming a protective layer and spurring a host of new adaptations for defense, pollination, and dispersal. One or more carpels make up what is considered the female portion of a typical angiosperm flower, including the ovary, stigma, and style.
caryopsis A type of fruit generally understood as the “seeds” of grasses.
cereal An annual, grain-bearing grass (e.g., wheat, barley, rye, oats, corn, rice).
chromosome The structure that bears the genetic information of a plant or animal. Chromosomes consist of the double-helix DNA molecule and surrounding proteins and serve as bulk units of inheritance between generations. In sexual reproduction, individuals receive half their chromosomes from each parent.
coevolution Process of evolution where changes in one organism spur changes in another. Traditionally, coevolution has been defined as a reciprocal interaction between two species, but it is now understood to be far more nuanced, producing changes within networks of interacting species that can vary across geography and through time.
copra The “meat” of a coconut, formed from solid, cellular endosperm.
cotyledon The embryonic leaf of a baby plant, also called a “seed leaf.” Cotyledons are well known to gardeners as the first leaves of germinating seedlings, and are also familiar when they are particularly large and tasty within the seed itself (e.g., the two halves of a peanut).
Cretaceous The final period of the Mesozoic Era, following the Jurassic and lasting from 146 million to 65 million years ago.
cytotoxin A poison that physically kills individual cells, as opposed to a neurotoxin, which causes paralysis or other damage to the nervous system.
dicot A major group of flowering plants defined by the presence of two cotyledons (di-cot) in the seed.
diploid The condition of having two sets of chromosomes, one from each parent.
dormancy Generally understood as the period of inactivity between the maturation of a seed and its germination. Technically, true dormancy applies only to those seeds that actively resist germination until various physical or chemical requirements are met (e.g., changes in light, temperature, and moisture, or exposure to wood smoke).
electron micrograph An image taken at extreme magnification by an electron microscope.
eliasome A rich, fatty packet attached to a seed to encourage seed dispersal by ants.
embryo In general, an unborn offspring. In botany, this term refers to the baby plant found within a seed.
emulsifier A substance (e.g., lecithin) added to stabilize the suspension of one liquid within another. In food products, emulsions are usually oils or fats suspended in water (e.g., mayonnaise), but can also be water in a fat (e.g., butter). Emulsifiers can also help suspend particles in a liquid, as with sugar and chocolate solids in cocoa butter.
endocarp The innermost layer of a fruit, often hardened to protect the seed.
endorphin One of a group of hormones secreted by the central nervous system. Endorphins are generally believed to be involved in regulating pain and pleasure responses.
endosperm An important tissue for the storage of nutrition in seeds.
In angiosperms, it is technically a triploid product of pollination. In gymnosperms, this role is played by the megagametophyte.
endozoochory Literally, “going abroad within animals.” The term refers to the seed dispersal strategy of being consumed, transported, and deposited by an animal.
enzyme Compounds, usually proteins, produced to catalyze a chemical reaction within an organism.
epicotyl Literally, “above the leaf.” It refers to the stem-like portion of a baby plant that is above the seed leaves and below the shoot, or plumule.
gametophyte Literally, “gamete-producing plant.” It refers to an independent generation in the spore-plant life cycle that produces eggs and sperm. In ferns, for example, it is a tiny, separate plant that grows from a spore and lives briefly in damp soil.
gene A specific location along a chromosome, where the shape and pattern of the DNA determine a specific trait.
genetically modified organism (GMO) A plant, animal, or microbe whose genetic code has been artificially altered, typically by the deletion or manipulation of genes, or by inserting genes from another organism.
germination The awakening of a seed. Technically, this process begins with water uptake (see imbibation) and ends when the radicle emerges from the seed coat. More generally, it includes the full emergence and establishment of the baby plant’s root and shoot.
grain Cereals (e.g., wheat, rice) and other similar crops (e.g., quinoa, buckwheat).
gymnosperm Literally, “naked seed.” The gymnosperms are a major group of seed plants defined by the lack of a carpel or enclosure around the seed.
hormone Any of a range of compounds that regulate growth, development, and other processes within a plant or animal.
hybrid A cross between two species, or between two distinct varieties of the same species.
hypocotyl Literally, “below the leaf.” The term refers to the stem-like portion of a baby plant that is beneath the seed leaves and above the root, or radicle.
imbibation The rapid uptake of water by a seed that signals the beginning of germination.
in situ Latin for “in place.” This phrase is commonly used in conservation and the natural sciences to describe activities within the natural habitat of a species. (Ex situ, in contrast, describes the study or conservation of a species in a zoo or nursery setting).
kernel A term for seed usually applied to cereals or to the soft, edible portion of tree nuts.
lecithin A fatty substance extracted from the storage oils in certain seeds, including soybeans, rape seeds, cottonseeds, and sunflower seeds. It is used as an emulsifier in food products and also as a cholesterol-reducing dietary supplement.
megagametophyte Literally, the “large-gamete-producing plant.” The term refers to egg-producing tissues that are a stand-alone plant in old lineages like the spike moss, but are incorporated into the flowering parts of seed plants. The megagametophyte produces the egg, and then its tissues are often included as part of the seed. Conifers and other gymnosperms, for example, pack the energy (or “lunch”) for their seeds in the megagametophyte.
meiosis Cell division that produces eggs and sperm or pollen. Instead of typical division (mitosis), where all chromosomes are duplicated, meisosis results in cells containing only half the normal chromosome allotment.
meristem The parts of a plant where cell division takes place, typically found at the tips of roots and shoots, and also around the perimeters of the stems and trunks of woody species.
metabolism The sum of all chemical reactions and processes occurring within an organism, generally considered the basis of life.
monocot A major group of flowering plants, defined by having one cotyledon (mono-cot) in the seed.
paleobotany The study of ancient plants.
Pennsylvanian A sub-period of the Carboniferous Period, also referred to as the Upper Carboniferous, which lasted from 323 million to 290 million years ago.
perisperm A starchy storage tissue found in seeds alongside (or, rarely, in place of) the endosperm.
Permian The sixth and final period of the Paleozoic Era, following the Carboniferous and lasting from 290 million to 245 million years ago.
photosynthesis The use of sunlight to transform water and carbon dioxide into life-sustaining carbohydrates, producing oxygen as a by-product.
pip A term for seeds generally applied to small, hard seeds found within soft fruits.
plumule The shoot of a plant embryo.
pulse A term for the edible seeds of various leguminous crops, including beans, lentils, and chickpeas.
radiation A rapid divergence and diversification of new species from an ancestral form.
radicle The root of a plant embryo.
recalcitrant A seed that does not desiccate and lacks a truly quiescent or dormant stage.
ribosome An organelle within cells that regulates the translation and expression of genetic information to produce proteins.
seed coat The outermost layer of the true seed, often serving protective, waterproofing, or dispersal functions, and sometimes intermingled with surrounding fruit tissues.
spore A tiny reproductive unit used by ferns, mosses, spike mosses, and other ancient plant groups. The seed habit evolved from the spore plants.
stamen The “male” part of the flower, bearing pollen-producing anthers.
stigma The area of the pistil, or “female” part of a flower, that receives the pollen.
tetraploid The condition of having four sets of chromosomes, two from each parent.
Theophrastus A student of and successor to Aristotle at the Lyceum. He is particularly well-known for his plant studies, and is often called “the father of botany.”
triploid The condition of having three sets of chromosomes, derived from hybridization between diploid and tetraploid parents.