Plant Biology Terms

Plant Biology Terms

Alternation of Generations

A weird, funky lifestyle that all plants and some algae have. Each generation of plants alternates being haploid (n) or diploid (2n)—that is, every other generation has half the genetic information that the others have. Even though the plant only has half the genetic information, it can still make a whole plant. A sporophyte generation (2n) makes a gametophyte (n) plant that then makes a sporophyte, and this process goes on and on, generation after generation.

Angiosperm

A flowering plant. Yep, the ones with all the pretty petals and yummy fruits, like apples, cherries, and watermelon? Where's a fruit stand when you need one? Angiosperms are also the most common plant group on Earth.

Apical

Refers to the tip of the plant. If you climb to the top of the mountain, you’re at the apex. Same idea with a plant, but apical can refer to both the tip of the shoots and the tip of the roots.

Apical meristem

A zone at the tip of a shoot or root where lots of cell division occurs, adding to new growth. Consider it one of the main construction zones of the plant.

Bud scale

Modified leaves that form a scale, covering a new bud. Bud scales protect buds before they open up and grow into shoots.

Cohesion-tension theory

The explanation for water movement in the xylem. The water is under tension, because it is evaporating out of the leaves. Cohesion makes water molecules stick together, so a column of water moves as one entity instead of many molecules moving separately.

Collenchyma

A cell type that functions in supporting the plant. You can find an example of collenchyma cells in stalks of celery—those wispy strands running the length of the celery are collenchyma cells.

Cotyledon

A seed leaf. The cotyledons store nutrients inside the seed, and as a seed germinates, the cotyledons give those nutrients to the growing plant. The number of cotyledons is an important distinguishing factor between monocots and eudicots, so stay tuned for that.

Epidermis

The outermost layer of cells. Humans have this layer too, but ours aren’t green.

Eudicot

A member of a large group of flowering plants that is evolutionarily advanced.

Fertilization

The fusion of two haploid gametes to make a diploid zygote.

Gamete

A reproductive cell or germ cell in sexually reproducing organisms. Gametes are haploid: they carry a single set of unpaired chromosomes. In females they are called eggs, and in males, they are called sperm.

Gametophyte

A plant that produces gametes (sperm and eggs).

Gymnosperm

A group of seed plants whose seeds are not enclosed by an ovary or fruit. They may produce cones and do not have flowers. Gymnosperm shares the same root word as gymnastics and gymnasium, meaning "naked." Reading this definition and then showing up to gym class in your birthday suit is not what we had in mind. At all.

Heartwood

The innermost, hardest wood of a tree. Compare to sapwood.

Intercalary meristem

A region of cell growth at the base of nodes and leaves. Only found in monocots.

Lateral

Refers to the side of the plant. See lateral meristem, below.

Lateral meristem

A zone of high cell division activity that creates width, also known as secondary growth. Both the vascular cambium and the cork cambium are lateral meristems. Compare to apical meristem.

Macronutrient

One of the six nutrients that plants need in large quantities. Primary macronutrients are nitrogen (N), phosphorus (P) and potassium (K). Secondary macronutrients, needed in less quantity, are calcium (Ca), sulfur (S) and magnesium (Mg).

Micronutrient

A nutrient that is essential to plant nutrition but only in small quantities.

Meristem

An area of the plant where lots of cell division occurs. There is a lot of hustle and bustle in the meristems, because new cells formed in a meristem are continuously adding to length or width of the plant.

Mesophyll

The middle layer of leaf tissue. If a leaf were a sandwich, the lower and upper epidermis would be the bread and the mesophyll would be meat or cheese.

Monocots

A group of plants that are all evolutionarily related, and are distinguished by the fact that they have one cotyledon (seed leaf). Just because they only have one seed leaf doesn’t make them inferior—some of the most important food plants are monocots, such as grasses. Other monocots, such as orchids and lilies, are prized for their beauty. Other traits monocots share are shallow, fibrous roots; floral parts in multiples of threes; and parallel veins.

Net venation

The web-like pattern of veins in the leaves of eudicots.

Parallel Venation

The pattern of veins in a monocot leaf. Veins run parallel to each other, instead of creating a big web—like they do in eudicot leaves. Though it sounds like a Silicon Valley buzzword, it is not.

Parenchyma

The most common plant cell type. Parenchyma cells are involved in storage, wound repair, and are the site of photosynthesis.

Phloem

A type of vascular tissue that transports sugars around the plant. Phloem flows from places where sugar is concentrated to where it is less concentrated. This tendency is called following a concentration gradient. Insert phlegm joke about boogers here.

Phyllotaxy

The arrangement of leaves around the plant stem. A plant maximizes the solar energy it receives by using feng shui to arrange its leaves.

Pollen

The dispersal unit for plant sperm. Pollen houses the male gametophyte and carries it to new places. The amount of pollen plants make depends on how they are pollinated: wind-pollinated plants make much more pollen than animal-pollinated plants, because they will inevitably lose some. Animal-pollinated plants can afford to make less pollen since they have dedicated pollen transfer agents (pollinators) that they entice with sweet nectar rewards.

Pollinator

An animal that transfers pollen between plants of the same type, whether willingly or unwillingly. Flowering plants have devised lots of tricks to deceive pollinators. Orchids are notorious tricksters, as their flowers can look like female bees. When a male bee sees the flower, he tries to mate with it, transferring pollen in the process. The bee doesn’t even get nectar in return for its effort!

Pressure-flow hypothesis

The explanation for phloem movement. Phloem flows from areas where sugar is made to areas low in sugar because of turgor pressure.

Primary growth

Growth that elongates the plant, but doesn’t make it wider. Primary growth originates at one of the apical meristems (shoot or root).

Rhizome

A specialized stem that grows underground and functions as a storage organ. Rhizomes are often confused with roots by the naïve observer. However, you Shmoopers will be able to tell your friends that potatoes and ginger are rhizomes, but onions are not.

Roots

The roots of a quadratic expression in x are the values of x that make the expression equal to 0.

Root cap

A protective cover for the tip of the root. No, this isn’t what plants wear to baseball games, even if they’re rooting for the home team. (It’s okay to groan here.) Root caps protect the root apical meristems and allow roots to burrow through rocky soil, water mains, and whatever else they can get their dirty little hands on.

Sapwood

The living, outermost wood in a tree. Sapwood is where the xylem carries water through the tree, and is also softer than the hard heartwood in the center of the tree.

Sclerenchyma

A rigid cell that functions in supporting of the plant.

Secondary growth

Adds width to a plant. Secondary growth originates at a lateral meristem and helps the plant stem widen.

Seed

A little bundle of joy containing genetic material to make a new plant, and nourishment for the baby plant as it starts growing. Higher plants (gymnosperms and angiosperms) have seeds, but more primitive plants such as ferns and mosses do not.

Sieve plate

The porous cell walls in between two sieve elements (phloem cells). Sieve plates have holes in them, allowing liquid to move from one sieve element to the next. You wouldn’t want to eat dinner on a sieve plate.

Spore

A single haploid cell that contains the genetic information necessary to make a new plant.

Sporophyte

A spore-bearing plant; also the dominant plant type of ferns, gymnosperms, and angiosperms.

Springwood

Wood that is made with big cells during times when water and nutrients are bountiful, such as in the spring.

Stoma

A pore in the epidermis of a leaf or stem that allows gas exchange. The plural of stoma is stomata, but one stoma can also be called a stomate. Stomata are controlled by guard cells.

Sugar sink

An area of the plant that receives sugars from the phloem.

Sugar source

An area of the plant that produces sugars, such as leaves, or releases sugars from storage, such as roots during certain parts of the year.

Summerwood

Wood made later in the year than springwood, when water and nutrients are not as plentiful. Cells in summerwood tend to be smaller than those in springwood.

Tissue

A group of cells that function together in some way.

Tracheophyte

A plant with a vascular system. Plants do not have tracheas.

Trichome

A small hair that arises from an epidermal cell and functions in protection and prevention of water loss.

Vascular

A characteristics that relates to transport of water and nutrients in the plant body. Animals also have vascular systems. Plant-animal sharing time.

Venation

The arrangement of veins in a leaf. This can help classify a plant in its taxonomic group.

Xylem

The water-conducting vascular tissue of a plant. Not…xylemophone.

Roots of Common Terms in Plant Biology

Roots: words and plants both have them.

(L – Latin, G – Greek)

Angiosperm

angio = case or capsule (G); sperm = seed (G) 

Antheridium

(plural antheridia): anthe = pollen or bloom (L); idium = small (G) 

Apical

apex = top (L)

Collenchyma

from kolla = glue (G); enkhuma = infusion (G)

Cyte or cyto

cell (G) "Cyto" is found at the beginning of a word, "cyte" ends a word.

Dormancy

dormire = to sleep (L) 

 Diploid

di =two (G); ploid = number of sets of chromosomes (G). 

Gametophyte

Gameto = gamete-producing, from gamete (G); phyte = plant (G). Gametes are sperm or eggs. "phyt-" can be used at the beginning of a word ("phyto…") or at the end ("sporophyte", "epiphyte") 

Gymnosperm

gymno = naked (G); sperm = seed (G) 

Lateral

side (L) 

Microstrobilus

micro= small or tiny (G); strobilos from strephein = to twist (G) 

Megaspore

mega = big (G); spore = seed (G)

Meristem

from meristos = divisible (G)

Mesophyll

meso = middle (G); phyll = leaf (G) 

Parenchyma

from parenkhuma = "something poured in beside" (G); para = beside (G); enkhuma = infusion (G) 

Phloem

phloos = bark (G); in trees, phloem is located just inside the bark and old layers of phloem cells make up bark 

Photosynthesis

photo = light (G); synthesis = putting together (G) 

Phyllotaxy

phyllo = leaf (G); taxis = arrangement (G) 

Sclerenchyma

sclero from skleros = hard (G); chyma = infusion (G) 

Sporophyll

sporo = spore-producing (G); phyll = leaf (G) In the sections that follow, you’ll encounter at least three spore-producing things: You’ll see sporophytes (plants that produce spores), sporophylls (leaves that bear spores) and sporocytes (cells that produce spores) 

Tracheophyte = tracheo

artery (G); phyte = plant (G)