Lecture 6: Plant morphology

Question 1

physical features of grasses

Answer 1

• long narrow leaves
• monocotyledons -> one embryonic leaf in seed
• cylindrical jointed stems
• fibrous root system
• each tiller produces new roots, stem, seed and leaves.

Question 2

useful characterisitics of grasses in pastures

Answer 2

• 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

Question 3

what are the growth patterns possible for grasses

Answer 3

1. Bunch-type/tillers/caespitose
2. Stoloniferous
3. Rhizomes

Question 4

what is bunch-type/caespitose growing grass

Answer 4

regular looking grass, fluffy and growing upwards

Question 5

what is Stoloniferous growing grass

Answer 5

• trail on ground
• each stolon grows a root
• horizontal growth above surface of soil
• all connected above soil

Question 6

what is Rhizomes growing grass

Answer 6

• grow horizontally but connected beneath the surface
• rooting in each stolon

Question 7

what species of grass use C3 and C4 photo?

Answer 7

• cool species use C3
• warm species use C4

Question 8

grass stages of growth

Answer 8

1. germination
2. vegetative stage
3. elongation
4. reproductive stage

Question 9

explain gemination stage in grasses

Answer 9

• 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

Question 10

explain vegetative stage in grasses

Answer 10

• growth of leaves
• each new leaf produces axillary bud = new tiller forming
• leaves form blades from the sheath

Question 11

explain elongation in grasses

Answer 11

• lengthening upwards
• seedhead pushes through highest sheath
• increases when longer days and higher temp

Question 12

explain reproductive stage in grasses

Answer 12

• 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

Question 13

list some temperate grass species

Answer 13

annual -> ryegrass, annual barely grass, annual silver grass

perennial -> perennial ryegrass

Question 14

what are some challenges with grasses in pasture

Answer 14

• need to be rested -> favoured by intermittent or rotational grazing
• when in dry phase grass will be more fibrous and less nutritive value

Question 15

how much atmospheric nitrgoen can legumes convert

Answer 15

25kg N fixed per tonne of legume Dry Matter

Question 16

why are legumes good in pasture

Answer 16

• 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

Question 17

explain germination phase for legumes

Answer 17

• 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

Question 18

explain Development stage of legumes

Answer 18

• terminal bud at top of stem (grow from top down),
• if eaten off, axillary bud produces more branching in response

Question 19

explain Reproduction stage of legumes

Answer 19

• flowering
• cross-pollinated by insects
• inflorescence (bunch of flowers) arises from bud at shoot apex or leaf apex

Question 20

list some Temperate legume species

Answer 20

• annual forages = annual clovers, annual medics
• Perennial forages = Lucerne

Question 21

what does the constant turnover in grasses mean?

Answer 21

• 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