Pastures 2 Flashcards
(17 cards)
Understand key physical features of grasses and legumes
Grasses
- Cylindrical jointed stems
- hollow stem with nodes that have leaves coming out of them
- Long, narrow leaves with parallel veins
- Leaves alternate and in one plane
- Fibrous root system arising from nodes of the stem
- shallow roots
- Characteristic flowers (trimerous) and embryos
- Monocotyledons
- one embryonic leaf in seed
- Most are diploid (2 sets of chromosomes), but some tetraploid rygrasses)
Understand key physical features of grasses and legumes
Legumes
- Annual, biennial or dicotyledons
- Valued for their ability to fix nitrogen -> source of nitrogen for pastures, crops and animals
- High digestibility and nutritive value for livestock and ‘break-crop’ in mixed farms
Understand growth forms and habits of grasses and legumes
Grasses - Duration
- Annuals die each year after they have produced seed
- Biennials die every two years after they have produced seed
- Perennials produce both vegetative and flowering shoots each year for a few to many years – can get seed as well
Understand growth forms and habits of grasses and legumes
Grasses - Habit
- Bunch type
- tillers
- Stoloniferous
- stolons trail on soil surface; root at nodes, green, normal leaves
- Rhizomatous
- rhizomes grow beneath soil surface; white, small, scale-like leaves
- Can spread from a single plant
- even when stolons or rhizomes are cut the two plants will keep growing separately
- Multiple connected growth units called tillers
- Each tiller produces roots and leaves when vegetative, plus stem and seed head when reproduced
- Each tiller has the same number of leaves (e.g. ryegrass will only have three leaves
- if a fourth leaf begins to grow a previous one will die)
Understand growth forms and habits of grasses and legumes
Grasses - Seeds
- Grass seed consists of endosperm (large store of starch) and an embryo
- Embryo consists of a primary shoot (plumule) and root (radicle) and scutellum (first$leaf)
Understand growth forms and habits of grasses and legumes
Legumes - Seeds
- After fertilisation, the growing seeds enlarge and the ovary wall grows into the pod
- The embryo within the seed consists of two cotyledons that enclose the embryo
- Legume seeds contain little or no endosperm; cotyledons serve as the energy source for embryo during germination
- Legumes have harder seeds than grass
- Mechanism of seed dormancy allows formation of a persistent seed bank
- Impermeable layer in the seed coat prevents water uptake and germination
- Hard seed breaks down dependent on temperature and species
Understand key processes associated with germination, vegetative growth and seed production
(Grass - Germination)
- Uptake of water by the seed stimulates respiration, cell division and secretion of enzymes which break down the starch in the endosperm into sugars
- Sugars pass to embryo to support growth of primary root and shoot
Understand key processes associated with germination, vegetative growth and seed production
(Grass - Vegetative growth)
- Regrowth occurs from the shoot apex at the base of the stem
Understand key processes associated with germination, vegetative growth and seed production
(Grass - Leaf and tiller formation)
- Leaves develop from apical meristem (‘growing$point’)
- When the meristem produces a leaf, it also produces an axillary bud
- Axillary buds can grow into new tillers, rhizomes or stolons
Understand key processes associated with germination, vegetative growth and seed production
(Grass - Leaf growth)
- Each grass leaf develops as a blade connected to a sheath which surrounds the stem above the node
- Cell division and expansion is restricted to meristem at leaf base
- New leaves grow up within the encircles bases of older leaves
Understand key processes associated with germination, vegetative growth and seed production
(Grass - Reproductive growth)
- Stimulated by day length and temperature
- Rapid expansion of stem which lifts the shoot apex above the soil surface
- Reproductive structures (inflorescence) develop from the shoot apex
- Pollen from anthers fertilises the ovules within the ovary which develops into grass seed
Understand key processes associated with germination, vegetative growth and seed production
(Grass)
- Germination
- Vegetation growth
- Leaf and tiller formation
- Leaf growth
- Reproduction growth
- Faster growth than legumes, especially in winter
- Generally more easily prehended (taller, thus can be accessed and eaten more readily)
- Responds to nitrogen fertilisers
Understand key processes associated with germination, vegetative growth and seed production
(Legumes)
- Germination
- Stem and branch development
- Leaf growth
- Reproductive growth
Understand key processes associated with germination, vegetative growth and seed production
(Legumes - Germination)
- Seed imbibes water resulting in growth of tap root and eventually secondary roots
- Cotyledons pulled above soil surface, emergence of unifoliolate leaf and first trifoliolate leaf
- Main stem elongates and a leaf is produced as nodule
- Axillary buds at the cotyledonary node form new shoots or branches
- If a terminal node is removed, branching is stimulated
Understand key processes associated with germination, vegetative growth and seed production
(Legumes - Stem and branch development)
- The primary growing points of legume shoots are the terminal bud (shoot apex) located at tip of stems and end of branches and stolons
- Removal of terminal buds stimulates branching from leaf axils, nodes or crown
Understand key processes associated with germination, vegetative growth and seed production
(Legumes - Leaf growth)
- Like grass, growing point lays down ‘primordia’ at nodes from which leaves develop
- For trifolium species, a trifoliate lamina (three leaflets) is attached by a petiole to its node
- Cell division and expansion take place uniformly across leaflets
Understand key processes associated with germination, vegetative growth and seed production
(Legumes - Reproduction growth)
- Flowering is influenced mainly by temperature and photoperiod
- The inflorescence arises from a bud either at the shoot apex or leaf apex
- The number of flowers per inflorescence varies between species
- Most legumes are cross pollinated by insects
- Flowers and seed are eaten by livestock
