F2 hybrid

F2 hybrid [ Genetics ]
Abbreviation: F2

Dictionary of botanic terminology - index of names

The second filial (= F2 ) generation of offspring obtained when F1-Hybrids (first-cross individuals) are crossed randomly among themselves.

This is the product obtained by self-fertilization or crossing inter se of two interbreeding offspring of the first filial generation F1. The progeny within an F2 generation will be more variable phenotypically than the F1. The characteristics of individual vary greatly, offspring unlike themselves

In F2 hybrid it is noticeable the happening of inbreeding depression ( compare whit: hybrid vigour ) which is the phenomenon that happens when plants self-pollinate and homozygosity increases. The more a species is inbred (i.e., the more self-pollinated), the more genes at which the pairs of alleles are the same. Self-pollination or inbreeding leads to an increase in homozygosity, and a decrease in heterozygosity. This usually leads to a loss of vigour.

Advertising

Holdfast roots [ Botany ]
Dictionary of botanic terminology - index of names

Some species of climbing plants develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place.

Climbing plants, like the poison ivy (Toxicodendron radicans), Boston ivy (Parthenocissus tricuspidata), and trumpet creeper (Campsis radicans), develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place. Usually the Holdfast roots die at the end of the first season, but in some species they are perennial. In the tropics some of the large climbing plants have hold-fast roots by which they attach themselves, and long, cord-like roots that extend downward through the air and may lengthen and branch for several years until they strike the soil and become absorbent roots.

Major references and further lectures:
1) E. N. Transeau “General Botany” Discovery Publishing House, 1994