Legume structure and morphology (1-28-2020)

crown-forming legumes

(e.g. alfalfa): The taproot survives until the plant dies

legume leaves

-Arise from alternate positions in the stem -Unifoliate: Single leaf attached to petiole -Trifoliate: Three leaflets attached to petiole through petiolules -Stipules: Leaflike appendages attached to the stem near junction with petiole -Petiole: Stalk that connects leaf to stem -Petiolules: Short-stalks that attach individual leaflets to distal end of petiole.

legume root types

-Crown-forming legumes (e.g. alfalfa): The taproot survives until the plant dies -Clone-forming legumes (e.g. white clover): The taproot dies within 2 yr, but plant survives through rooted stolons: -These adventitious roots are less drought resistant (shallower).

crown(stem base)

-It is a complex structure between the shoots and roots, and contains buds from which new growth arises. -Grazing-tolerant legumes have many crown buds and stems, and have lowset broad crowns In drought conditions alfalfa is more resistant than white clover due to its adventitious roots

development stages

-Stages: vegetative, bud, bloom, and mature. -Onset of flowering signals a continuing decline in forage quality due to reduction of leaf growth and fibrous and lignified stems

legume stems

-Upright growth: Shoot apex or terminal bud of the stem is always located at the tip (top of the canopy) -Alfalfa, sweetclover, etc. -Red and alsike clovers: Long petioles display leaves at the top of the canopy, so shoot apex remains low in the canopy.

legume stems

-When the terminal bud is cut or grazed -Upward growth of main stem halts -Successive growth needs to come from axillary buds in lower nodes, especially those in the crown area (stem base). -Prostrate creeping growth: Species like white clover have stolons with shoot apices near ground level. -Mowing or grazing only removes leaf blades and petioles with little effect on shoot apices

legume seedling emergence

-epigeal: cotyledons pushed above soil by the elongating hypocotyl -hypocotyl: embryo stem part beneath cotyledons and directly above the root -most forage legumes -advantage: cotyledons can photosynthesize -hypogeal: cotyledons remain belowground and the epicotyl pulls the plumule above ground -advantage is that if plumule is damages regrowth can still happen.

legumes

-family=Fabaceae -over 18,000 species -All dicots, herbaceous and broadleafed

seedling root contractile growth

-first node (where cotyledons were, and crown forms) is gradually pulled underground -Occurs in many legumes with epigeal emergence -Deeper crown placement ↑ persistence, grazing tolerance, and resistance to heat and freezing.

legume seedling

-legumes can produce "hard seeds" that do not germinate immediately -should be <10% of purchased seed -sometimes difficult to achieve for winter hardy cultivars -corrected by increasing seed rates -most seed producers blend seed batches to achieve this target -they can become softened by wetting and drying, freezing and thawing, or by mechanical scarification. -best method is species dependent.

hairy vetch

-pinnately multifoliate

birdsfoot trefoil

-pinnately pentafoliate

legume inflorescence types

-raceme: the florets are with pedicels of about the same length, which are attached along the elongate and unbranched peduncle of the inflorescence -umbel: the florets are with pedicels, which are all attached at about the same point at the end of the peduncle.

legume root symbiosis

-symbiotic rhizobia bacteria that infect root hairs cause development of nodules -nodules that contain active N-fixing bacteria have a pink to red color.

legumes

-term legume indicates the type of fruit that is characteristics of this family. -one-chambered fruit that dehisces(opens) along its two seams(sutures)

established plant: root system

-the primary root system of legumes consists of a prominent, central taproot(1-8 m deep) -the taproot may become branched with numerous lateral roots.

legume seedling root development

-the radicle penetrates the seed coat and develops a simple tapering taproot

false

A deer grazes an alfalfa seedling that has emerged and removes the tip of the plant which contains the growing point. This is totally fine as the alfalfa seedling will be able to regrow. * alfalfa is epigeal

shoots

A typical shoot consists of: Stems (internodes and nodes) -Branches -Leaves -Inflorescences -Fruits (seepods). -1-2 m long.

alfalfa

Alfalfa is more drought resistant than white clover, but it is because of its taproot that can penetrate several meters into the soil vs. the shallow adventitious roots in white clover.

legume seed components

Consists of seed coat, hilum, micropyle, and embryo. -The embryo has 2 cotyledons and consists of the radicle (primary root), and an epicotyl (plumule). -Legume seeds have little endosperm, the cotyledons act as the storage organ -Thus, most legumes are planted shallow (~0.25-0.5 inch deep) due to low reserves.

false

In drought conditions alfalfa is more resistant than white clover due to its adventitious roots

flowers

Individual flowers are papilionaceous (i.e. butterfly-like). -Consists of 5 petals (a large standard or banner, 2 lateral wings, and 2 that are fused to form the keel).

stipules

Leaflike appendages attached to the stem near junction with petiole

red and alsike clover

Long petioles display leaves at the top of the canopy, so shoot apex remains low in the canopy.

upright growth

Shoot apex or terminal bud of the stem is always located at the tip (top of the canopy)

petiolules

Short-stalks that attach individual leaflets to distal end of petiole.

unifoliate

Single leaf attached to petiole

prostate creeping growth

Species like white clover have stolons with shoot apices near ground level. -Mowing or grazing only removes leaf blades and petioles with little effect on shoot apices

petiole

Stalk that connects leaf to stem

trifoliate

Three leaflets attached to petiole through petiolules

palmately

all petiolules length equal

legume pods

are one-chambered fruits that contain a single seed or multiple seeds in a single row

pinnately

central petiolule longer than others

white clover

compact raceme

epigeal

cotyledons pushed above soil by the elongating hypocotyl -most forage legumes -advantage: cotyledons can photosynthesize

hypogeal

cotyledons remain belowground and the epicotyl pulls the plumule above ground -advantage is that if plumule is damages regrowth can still happen.

clone-forming legumes

e.g. white clover): The taproot dies within 2 yr, but plant survives through rooted stolons: -These adventitious roots are less drought resistant (shallower).

hypocotyl

embryo stem part beneath cotyledons and directly above the root

white clover

palmately trifoliate

alfalfa

pinnately trifoliate

alfalfa

raceme

birdsfoot trefoil

umbel