Root

Rootstock

rootstock: a short, erect, more or less swollen structure at the junction of the root and shoot systems of a plant, cf. xylopodium. (Stevens, APG)

xylopodium: as found in fire-resistant plants in particular, a more or less massive underground storage structure formed from stems and/or roots allowing resprouting after fire, cf. root stock. (Stevens, APG)

grafting of cucumber on Cucurbita ficifolia rootstock
greffe de concombre sur les racines de Cucurbita ficifolia (au sens de "système racinaire")

MC. En anglais botanique moderne, rootstock est un synonyme de rhizome (Webster, RC, confirmé par Roel Lemmens)

rhizome: a slender to much swollen underground stem that grows more or less horizontally, cf. bulb, bulbil, caudex, corm, creeping stem, dropper, lignotuber, pseudobulb, runner, stolon, tuber, tiller, turion. (Stevens, APG)

rhizome, underground stem. A stem growing more or less horizontally below ground level is described as a rhizome. (Bell, 2008, 160).
tuber (root tuber). In contrast to a stem tuber, a root tuber will have a root cap, at least when very young, and it may bear lateral roots but will not bear a regular sequence of scale leaves subtending buds... Large woody swellings form on some trees and shrubs and can be partly of root tissue origin. Such woody structures are referred to as lignotubers. (Bell, 2008, 140).

rhizome, tige souterraine. On appelle rhizome une tige qui croît plus ou moins horizontalement dans le sol. (Bell, 1993, 130).
tubercule (racinaire). A l'inverse du tubercule caulinaire, le tubercule racinaire possède une coiffe, au moins aux stades les plus jeunes ; il peut porter des racines latérales, mais pas une séquence régulière de feuilles en écailles axillant des bourgeons... De grands renflements ligneux apparaissent chez certains arbres et arbustes, ils peuvent provenir en partie des tissus racinaires. On appelle lignotubers (Lacey) de telles structures racinaires. (Bell, 1993, 110-111).

the rootstock or dorsiventral stem, of root-like appearance, prostrate on or under ground, sending off rootlets, the apex progressively sending up stems or leaves;
= Caudex (J.S. Henslow);
= Radicle (Henslow). (Jackson, 1928)

en.: caudex
fr: caudex n. m. "Organe de réserve renflé et vivace situé à la base d'une plante caudiciforme, constitué soit par le système radiculaire, soit par la tige, ou par les deux. Note : Le caudex permet à la plante de résister à une période de sécheresse". (Grand Dictionnaire)

caudex: a ± short, thick, erect trunk or stem, somewhat above to somewhat below ground level, cf. bulb, bulbil, corm, creeping stem, dropper, lignotuber, pseudobulb, rhizome, runner, stolon, tuber, tiller, turion. (Stevens, APG)

cauduciform: a plant with an enlarged, swollen, usually water-storing basal portion of the stem. (Stevens, APG)

lignotuber: a woody swelling at the base of the shoot system below or just above the ground, containing adventitious buds from which new shoots develop if the top of the plant is cut off or burnt, common in many fire-tolerant shrubs, cf. bulb, bulbil, caudex, corm, creeping stem, dropper, pseudobulb, rhizome, runner, stolon, tuber, tiller, turion. (Stevens, APG)