F1 hybrid

F1 hybrid [ Genetics - Botany ]
Abbreviation: F1

Dictionary of botanic terminology - index of names

The first filial (= F1) generation of offspring plants derived by a cross-pollination between two compatible but genetically different parent. If each parent is truebred (homozygous), the F1 individuals resemble each other.

F1 hybrids (first-generation hybrid) derived from a cross between two homozygous cultivars (or from two unrelated population, species or genus) can have advantages, including the robust growth known as "hybrid vigour", homogeneity (A fairly uniform phenotype), greatest disease resistance and when the right inbreds are combined, the hybrid can explode with unimaginable improvements.
The F1 may have desired qualities of either or both parents. Seed saved from the cross-pollinated female fruit or plant is a F1 hybrid seed.
F1 hybrids involving different species are very often sterile.
Plant derived from cross-pollination among F1 hybrids ( called second filial generation or F2) are unpredictable and produce offspring unlike themselves. In addition the hybrid vigour is is usually suppressed in subsequent generations (Inbreeding depression).

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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