Lecture 6: Plant morphology Flashcards
physical features of grasses
- long narrow leaves
- monocotyledons -> one embryonic leaf in seed
- cylindrical jointed stems
- fibrous root system
- each tiller produces new roots, stem, seed and leaves.
useful characterisitics of grasses in pastures
- faster growth than legumes
- more easily prehended
- respond to N2 fertilisers
- constant turnover
- cool or warm but can handle change better
- Massive number of species -> adapted to many climates
- large seeds so can be buried deeper (starch storage)
- some are tetraploid (4 chroms), so have broad leaves and more nutrients for ruminants
what are the growth patterns possible for grasses
- Bunch-type/tillers/caespitose
- Stoloniferous
- Rhizomes
what is bunch-type/caespitose growing grass
regular looking grass, fluffy and growing upwards
what is Stoloniferous growing grass
- trail on ground
- each stolon grows a root
- horizontal growth above surface of soil
- all connected above soil
what is Rhizomes growing grass
- grow horizontally but connected beneath the surface
- rooting in each stolon
what species of grass use C3 and C4 photo?
- cool species use C3
- warm species use C4
grass stages of growth
- germination
- vegetative stage
- elongation
- reproductive stage
explain gemination stage in grasses
- large, starch storing seed
- embryo has primary shoot, root and contains first leaf (scutellum)
- uptake of water by seed,
- respiration,
- cell division.
- Enzymes released, will break down starch for growth
explain vegetative stage in grasses
- growth of leaves
- each new leaf produces axillary bud = new tiller forming
- leaves form blades from the sheath
explain elongation in grasses
- lengthening upwards
- seedhead pushes through highest sheath
- increases when longer days and higher temp
explain reproductive stage in grasses
- reproductive structures (inflorescence) develop from the shoot apex (top of stem)
- pollen from anthers (pollen sacs) fertilise ovules within the ovary and develop into grass seed
list some temperate grass species
annual -> ryegrass, annual barely grass, annual silver grass
perennial -> perennial ryegrass
what are some challenges with grasses in pasture
- need to be rested -> favoured by intermittent or rotational grazing
- when in dry phase grass will be more fibrous and less nutritive value
how much atmospheric nitrgoen can legumes convert
25kg N fixed per tonne of legume Dry Matter
why are legumes good in pasture
- fix nitrogen for other plant and animal requirements = fast plant growth
- highly digestible and nutritious
- don’t need to eat as much dry matter to gain nutrients
- don’t need to be rested
- can resist the false break as seeds can become impermeable to water -> good for seed bank
explain germination phase for legumes
- after fertilisation, seed enlarges and ovary wall grows into a pod
- two cotyledons that enclose the embryo -> little to no endosperm so use cotyledons as energy source
explain Development stage of legumes
- terminal bud at top of stem (grow from top down),
- if eaten off, axillary bud produces more branching in response
explain Reproduction stage of legumes
- flowering
- cross-pollinated by insects
- inflorescence (bunch of flowers) arises from bud at shoot apex or leaf apex
list some Temperate legume species
- annual forages = annual clovers, annual medics
- Perennial forages = Lucerne
what does the constant turnover in grasses mean?
- each tiller can grow a maximum number of leaves
- remnant leaf grows first, 1st, 2nd, 3rd grow and remnant dies
- 4th grows and 1st leaf dies and so on
- only 3 at one time
