Fabaceae (fab-AY-see-ee)
Iconic Features
- Compound, often pinnate, leaves
- Most with characteristic pea flower
- Fruit is a legume (pea/bean pod)
Description (Jepson)
- Mostly herbaceous perennials
- Also may be annuals, shrubs, or trees
- Eudicotyledons (eudicots) – a major lineage of flowering plants including most plants traditionally described as dicots and generally characterized by
- 2 seed leaves (dicotyledon)
- Netted (reticulate) leaf venation
- Flower parts in fours and fives
- Pollen grains with 3 pores (tricolpate)
- Vascular bundles in stem arranged in a ring
- Taproot system
- Leaves
- Compound (divided into leaflets) and entire (with smooth margins); often pinnate (arranged along a common axis, like a feather)
- Generally alternate (1 leaf at each junction with stem)
- All have stipules (a pair of leaf-like structures at the base of the leaf stalk), some modified to spines or glands
- Flowers
- The Pea family is divided into subfamilies, each with a unique floral design, though flowers are generally bisexual and bilaterally symmetrical
- Pea subfamily (Faboideae / Papilionoideae), which includes most California species, have the characteristic pea flower, with 5 petals in a distinct arrangement
- Banner – large upper petal with 2 lobes
- Wings – 2 lateral petals
- Keel – 2 lower, united petals, forming a narrow ridge, like the keel of a boat
Pea Flower - Ovary superior (above the attachment of other flower parts)
- Fruit is a legume (a single-chambered seed pod that opens along 2 seams)
Notes
- Approximately 19,400 species worldwide
- Third largest plant family by number of species
- Economically important family, including many commercially-grown species that provide significant sources of protein (e.g. peanuts, soybeans, beans, clovers)
- Also includes highly weedy and invasive plants (e.g. broom, gorse, kudzu)
- Almost all species have nitrogen-fixing nodules on their roots
- Nodules host a bacteria (Rhizobium) that captures nitrogen gas (N2) from the air and converts it by a process called fixation into nitrogen compounds that plants can use
- Host plant provides the bacteria with carbohydrates produced by photosynthesis and minerals
- This symbiotic relationship allows Pea family members to grow in nitrogen-poor soil, like serpentine
- When the plant dies, the fixed nitrogen is released, fertilizing the soil for other plants
- Edgewood naturalist Paul Heiple notes that many Pea family members use some of their nitrogen to form alkaloid-based toxins to discourage browsers from eating their protein-rich foliage and fruits (Heiple 2020)
Specific References
Heiple, P. 2020, Jun. 14 & Jul. 2. Personal communications.
