Plant Science Terms - G

Gall - a growth on plant stems or leaves caused by abnormal cell growth stimulated by the feeding of some insects (e.g., aphids) or by viral, fungal, or bacterial infection or genetic abnormality

Genetically modified - a plant or animal that has had genetic material introduced to its genome from other organisms through artificial means

Genera (genus plural) - used when referring to more than one plant genus.  For instance, "the Petunia and Verbena genera have great garden applications."

Genes - basic units of hereditary material that dictate the characteristics of individuals

Genus - a subdivision of family in the classification of plants. Plants of the same genus share similarities mostly in flower characteristics and genetics. Plants in one genus usually cannot breed with plants of another genus. In addition, it is the first part of the two-part scientific name used for plants

Geography, plant - study of the distribution of plants throughout the world

Geotropism - turning or curving growth of plant parts in response to gravity. A root growing downward is an example. Geotropism is controlled largely by the hormone auxin

Germination - processes that begin after planting a seed or spore that lead to the initiation of active growth by the embryo, resulting in the rupture of seed coverings and the emergence of a new seedling plant capable of independent existence

Gibberellins (GAs) - plant hormones that regulate growth and influence various developmental processes, including stem elongation, germination, dormancy, flowering, sex expression, enzyme induction, and leaf and fruit senescence

Girdled or girdling - damaging, cutting, removing, or clamping of cambium all the way around a trunk or branch. Sometimes, girdling is done deliberately to kill an unwanted tree, but often it results from feeding by insects or rodents. Wires and ties used to support a tree can cause girdling, as can string trimmers

Girdled roots - a root system that has outgrown its pot to the extent that the roots are encircling the inside of the pot, restricting nutrient uptake

Glabrous - leaf surfaces that are hairless, smooth, and shiny

Glaucous - covered with a grayish, bluish, or whitish waxy coating that is easily rubbed off. Blue spruce needles are an example of glaucous leaves

Gradual metamorphosis - see Simple metamorphosis

Graft union - see Bud union

Grafting - a method of asexual plant propagation that joins two separate plant structures, such as a root and stem or two stems, so that by tissue regeneration they form a union and grow as one plant

Gravitational water - water in excess of a soil’s capacity. Drains downward to groundwater

Gray mold - fungal surface growth, gray in color

Green cone - an enclosed composting unit often used for composting food waste

Green manure - an herbaceous crop plowed under while green to enrich the soil

Ground color - color of a fruit before it ripens.

Groundcover - plants used for holding soil, controlling weeds, and providing leaf texture.

Growing season - period from the last spring freeze and the cessation of growth with the first freeze in the fall. In the United States this ranges from about 100 to 365 days

Growth regulator - compound applied to a plant to alter its growth in a specific way. May be a natural or synthetic substance. (See also Hormone)

Guard cells - pair of specialized parenchyma cells that border the pore, responsible for regulating the size of the opening. They swell to open the stoma and shrink to close it

Gummosis - exudation of sticky sap. In conifers, this is known as “resinosis”

Gymnosperm - class of plants that form seeds in open receptacles, often cones and not enclosed in an ovary (e.g., conifers).

Gynoecium - female portion of the flower, the pistil is also referred to as the gynoecium or "female house." The gynoecium is the innermost whorl of (one or more) pistils in a flower and is typically surrounded by the pollen-producing reproductive organs, the stamens, collectively called the androecium

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