Table 3.
Parenchymatous storage organs in non-woody plants exploited by people and ordinarily propagated vegetatively, primarily underground storage organs (USOs) (after Abrahamson, 1980; Hather, 1998, 1994a, 2000)
| Plant structure | Description | Examples |
|---|---|---|
| Bulb | Rounded underground storage organ comprised of a short stem surrounded by fleshy scale leaves or leaf bases | Garlic (Allium sativum); lily (Lilium spp.); onion (Allium cepa) |
| Bulbil | Tuber produced in the axil of a leaf capable of adventitious root growth. Propagation by fragmentation and adventitious growth | Bitter/cheeky yam (Dioscorea bulbifera) |
| Caudex | Vertical multimodal swelling of a stem base. Sometimes referred to as a pachycaul stem. This may or may not constitute the reproductive structure of the plant | Baobab (Adansonia spp.); cycads (Cycas spp., Zamia spp.); giant taro (Alocasia macrorrhiza); tree ferns (Alsophila spp.) |
| Corm | Vertical multimodal tuber of 1 year or more duration, producing ephemeral shoots. Each node on a corm has the capacity to produce daughter corms. Propagation by axillary replacement, fragmentation and adventitious growth | Canna (Canna edulis); cocoyam (Xanthosoma saggitifolium); eddoe (Colocasia antiquorum); elephant foot yam (Amorphophallus spp.); enset (Ensete ventricosum); fern (e.g. Pteridium esculentum); swamp taro (Cyrtosperma merkusii); taro (Colocasia esculenta); water chestnut (Eleocharis dulcis) |
| Rhizome | Perennial horizontal axis more or less homogenously swollen or unswollen supporting ephemeral leaves and flowering axes arising vertically at nodes. Propagation by fragmentation and adventitious growth | Arrowroot (Maranta arundinacea); galangal (Alpina sp.); ginger (Zingiber officinale); oca (Oxalis tuberosa); tumeric (Curcuma sp.); typha (Typha spp.) |
| Rhizome tuber | Multiple swollen regions along the length of, or terminally attached to, a rhizomatous axis. Propagation by fragmentation and adventitious growth | Cyperus (Cyperus spp.); Scirpus spp. |
| Root tuber | Swollen regions along the length of an otherwise unswollen root system. Occasional vegetative propagative capability by adventitious growth | Cassava/manioc (Manihot esculenta); leren (Calathea allouia); murnong (Microseris scapigera); pencil yam (Vigna lanceolata); sweet potato (Ipomoea batatas) |
| Stolon tuber | Swollen regions along the length of, and terminally attached to, a stolon. In the yams, swelling may be massive forming large, long or thick tubers. Propagation by fragmentation and adventitious growth. | Arrow head (Sagittaria sagittifolia); Plectranthus spp.; lotus root (Nelumbo nucifera); potato (Solanum tuberosum); yams (Dioscorea spp.) |
Classifications are not necessarily exclusive for a particular plant, given changes in plant structures during life cycles, such as rhizome–caudex in Typha spp.: Hather, 2000: p. 16). Many USOs are exploited by people for food and used for propagation; however, this is not always the case. For example, bananas (Musa cvs) are exploited for fruit and reproduced from suckers growing from a corm at the base of the pseudostem, while sweet potato (Ipomoea batatas) is exploited for root tubers and can be reproduced from root tubers and vine slips (stem cuttings).
Tap roots are excluded here, as although a swollen secondary root of a biennial or perennial herbaceous plant, the crops are ordinarily reproduced from seed, as a tap root has no vegetative propagative capability.