Grass Structures - Mechanisms for Growth
There are several ways that grasses can grow or grow back after defoliation, winter freezes, or other stresses. There are 5 different structures that enable a grass plant to grow. The five are the apical meristem (meristem=tissues capable of growth), the intercalary meristem, basal buds, stolons, and rhizomes. Not all grass species have all five.
The Growing Point: apical and intercalary meristems
Many texts refer to "the growing point" of grasses. The growing point consists of two growth mechanisms. Within the growing point there is an apical dome containing the apical meristem and the primordium which will develop intercalary meristem. The apical dome contains apical meristems which push new leaves upward causing the grass plant to increase height and foliage. Intercalary meristems begin in the primordium and are pushed upward to become the base of each leaf blade. Much growth of a leaf is actually the expansion of the cells in the intercalary meristem. This expansion is conducive for photosynthesis and, if a leaf tip is removed, the intercalary cells continue to increase the leaf blade although the leaf tip will not regrow.
Buds are the sites for tillering. In the various texts there are many terms that refer to buds. Terms like sprouts, shoots, daughters, and tillers are used. Adjectives can also make the word buds more confusing. The literature refers to aerial buds, adventitious buds and basal buds. Basically, all buds are adventitious with basal buds referring to those new tillers arising from the base or crown area. Aerial buds, appearing at the lower nodes of the plant, occur in certain species.
Some species have extravaginal tillering. This means they send out lateral, underground growth which can root at the nodes and develop daughter plants. Grass species with rhizomes (underground stems) are sod forming and can be invasive.
StolonsAnother type of extravaginal tillering produces lateral, above-ground growth which can root at the nodes' stolons. Grass species with stolons (above ground stems) are sod forming and can be invasive. It is possible that a species may have both rhizomes and stolons but, generally, a species will have one or the other. Many species, called bunchgrasses, have neither rhizomes nor stolons. Tall fescue is considered a bunch grass but has short rhizomes.
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