Common name. Turnip. Family Brassicaceae.
Habit and leaf form. Herbs. Glaucous annual, or perennial. Leaves basal, or cauline. Plants with a basal concentration of leaves, or with neither basal nor terminal concentrations of leaves. Young stems cylindrical. To 0.5–1.5(–3) m high. Mesophytic. Leaves medium-sized to large; alternate; spiral; ‘herbaceous’; petiolate, or subsessile; sheathing to non-sheathing; simple; epulvinate. Leaf blades dissected, or entire; pinnately veined; cross-venulate; stem-clasping or not so. Leaves without stipules. Leaf blade margins entire, or serrate, or dentate. Leaves without a persistent basal meristem. Leaf anatomy. Hairs present (scattered), or absent; glandular hairs absent; complex hairs absent. Branched hairs absent. Extra-floral nectaries absent.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in racemes, or in corymbs. The terminal inflorescence unit racemose. Flowers pedicellate; ebracteate; ebracteolate; small to medium-sized; regular; 2 merous; cyclic. Floral receptacle with neither androphore nor gynophore. Free hypanthium absent. Hypogynous disk present; of separate members. Nectariferous glands 4. Perianth with distinct calyx and corolla; 8; 3 -whorled (K 2+2, C 4). Calyx present; 4; 2 -whorled; polysepalous; erect to spreading; decussate; regular. Sepals slightly saccate. Corolla present; 4; 1 -whorled; alternating with the calyx; polypetalous; imbricate, or contorted; regular; usually yellow. Petals obovate; clawed. Androecial members definite in number. Androecium 6. Androecial members branched (in that the inner whorl of 4 is derived from only 2 primordia); free of the perianth; markedly unequal; free of one another; 2 -whorled (2+4). Androecium exclusively of fertile stamens. Stamens 6 (2 outer anthers and 4 inner anthers in 2 pairs); tetradynamous; all more or less similar in shape; hypogynous, on receptacle, outer stamens lateral. Filaments not appendiculate. Anthers basifixed; non-versatile; dehiscing via longitudinal slits; introrse; unilocular to bilocular; tetrasporangiate. Pollen shed as single grains. Gynoecium 2 carpelled. The pistil 2 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary plurilocular; 2 locular. Locules secondarily divided by ‘false septa’. Gynoecium transverse. Ovary sessile. Gynoecium stylate. Styles 1; apical. Stigmas 1; commissural; more or less 2 - lobed; more or less capitate. Placentation parietal. Ovules 20–50 per locule (to ‘many’); with ventral raphe; non-arillate; anatropous.
Fruit and seed features. Fruit 10–100 mm long; non-fleshy; not an aggregate; dehiscent; a siliqua. Capsules valvular. Fruit 2 celled; (4–)12–50 seeded (few or none in the beak region). Seeds 2–50 per locule (to ‘many’). Seed rows per locule 1. Seeds scantily endospermic, or non-endospermic; mucous; small to medium sized; wingless (almost spherical). Embryo well differentiated. Cotyledons 2; folded; incumbent; conduplicate. Embryo bent.
Physiology, biochemistry. Mustard-oils present.
Special features. Fruit body distinctly differentiated into valve and beak regions. Beak containing seeds, or seedless. Replum present and complete. Fruit bilaterally compressed (or quadrangular), or terete. The inner (lateral) pair of sepals saccate basally for nectar storage, or not noticeably saccate. Petals not peculiarly elongated as in Stenopetalum. Nectariferous glands lateral and median. Siliquae moniliform, or not moniliform. Valves of the fruit neither winged nor keeled; conspicuously longitudinally veined; longitudinally 1 veined.
Etymology. From the Latin for "cabbage".