Terminology

Terminology

Adventitious (roots)

• Roots that arise from a stem or leaf; not arising from the true root (radicle)

Allele

• One form (of many) of a particular gene 

Cell

• The smallest structural and functional unit of an organism, typically microscopic and consisting of cytoplasm and a nucleus enclosed in a membrane

Centromere

• The region of a chromosome to which the spindles attach during cell division

Chromatid

• Each of the two threadlike strands into which a chromosome divides longitudinally during cell division. Each contains a double helix of DNA

Chromosome

• A threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

Collenchyma

• Specialized cells that have unevenly thickened primary walls that provide flexible support in herbaceous organs

Colonial organism

• Unicellular organisms that are found connected (tethered) to one-another in nature

Companion cells

• Specialized form of parenchyma that controls all of the cellular functions of a sieve element

Dermal

• Cells that compose the "skin" of the plant, such as the epidermis or bark

Diploid

• Having two sets of chromosomes in each cell; therefore two copies (alleles) of each gene

DNA, DeoxyriboNucleic Acid, 

• A self-replicating material present in nearly all living organisms as the main constituent of chromosomes. It is the carrier of genetic information.

Embryonic

• Immature cells that can actively divide to increase size of the organism

Eukaryote

• Organisms that possess organelles, such as a nucleus (e.g. plants, fungi, animals, algae)

Haploid

• Having a single set of chromosomes in each cell; therefore, only one copy (allele) of each gene

Herbaceous

• A plant that only has soft, green parts; not woody

Homologous (of chromosomes)

• Having the same structural features and pattern of genes. Being the same chromosome "number".

Interphase

• A portion of time in which a cell recovers from mitosis (post-Telophase), and/or prepares to enter mitosis or meiosis

Karyogamy

• Splitting of just the genetic material; chromosomes replicated in interphase and then divided 

Meiosis

• Cell division which creates four haploid cells from a single diploid cell

Meristem

• An area of embryonic cells that divide to provide growth (see primary meristems, peripheral meristems, etc.)

Mitosis

• Cell division which creates two identical cells from a single cell; growth

  • Anaphase: the third phase of mitosis or meiosis; chromatids begin to segregate and migrate to opposite ends of cell

  • Metaphase: the second phase of mitosis or meiosis; chromosomes line up on the equatorial plate and spindle fibers become visible 

  • Prophase: the first phase of mitosis or meiosis; the nuclear envelope starts to dissolve and chromosomes condense

  • Telophase: the fourth and final phase of mitosis or meiosis; the cell plate forms and the nuclear envelope begins to form 

Multicellular

• An organism that is composed of many cells

Organism

• A living creature, such as a plant, animal, or bacterium

Parenchyma

• Specialized cells that lack secondary walls, and form the bulk material of plants where storage occurs

  • Aerenchyma: parenchyma tissues that have abundant amounts of air spaces

  • Chlorenchyma: parenchyma tissues that have abundant amounts of chloroplasts for photosynthesis

Plasmogamy

• Fusion of cells' cytoplasm and organelles, such as gametes combining during fertilization 

Pollen

• The microspores of a seed plant. They are dispersed into the environment. A pollen grain contains the male gametophyte of the plant.

Prokaryote

• Organisms without an organized nucleus or organelles (e.g. bacteria)

Radicle

• The true root that emerges from the seed

RNA, RiboNucleic Acid

• A nucleic acid present in all living cells. Its principal role is to act as a messenger carrying instructions from DNA for controlling the synthesis of proteins, although in some viruses RNA rather than DNA carries the genetic information.

Sclerenchyma

• Specialized cells that have thick lignified secondary walls to provide rigid support in plants

Sieve cells

• Phloem cells that transport sugars, usually found in pteridophytes and gymnosperms 

Sieve tube elements

• Phloem cells that transport sugars, usually found in flowering plants

Tracheids

• Water-conducting and strengthening xylem cells, usually found in pteridophytes and gymnosperms 

Unicellular

• An organism that is one single cell

Vascular

• Specialized cells that move water, minerals, and/or sugars (e.g. xylem, phloem)

Vascular cambium

• A peripheral meristem that creates secondary growth in woody plants and increases the girth of the plant

Vessels

• Water-conducting xylem cells, usually found in flowering plants and some gnetophytes

Woody

• A plant morphology that possesses secondary xylem that formed from a vascular cambium