Lecture 14: Light interception 2. Evolution of crop plants Flashcards
light interception is affected by:
- the number of leaves (LAI)
- leaf duration - the longer leaves last the more light they will intercept
- leaf orientation (some, shape, vertical separation)
- AND
- Heliotropism (leaf movement)
- Structures other than leaves - awns, stems, ears
why is it optimal leaves move?!
No fixed leaf orientation can be optimal in the relation to a moving light source (the sun)
heliotropism:
moving of leaves in relation to the sun
Diaheliotropic:
leaves remain perpendicular to the sun
Paraheliotropic:
leaves remain parallel to the sun
-try to avoid light interception, may be under stress i.e. water stress
two forms of heliotropism:
- diaheliotropic
- paraheliotropic
solar trackers: & e.g
- orientate towards the sun
- soybean
- sunflower
- cotton
- townsville lucerne
photosynthesis is always a balancing act betwee
light interception and water loss
all aerial parts of grasses are ___ at earlier stages of development
GREEN
==photosynthesises!
Wheat structure:
- flag leaf: which subtends the ear (hugs), are erect and high in the canopy
- awns (spiky bits out v top)
source of photosynthates in wheat during development:
- ear formation: from the leaves
- Flowering (anthesis): from upper leaves and ear
- 2 weeks after flowering: flag leaf stem and ear
- 4 weeks after: flag leaf
WHEAT: anthesis occurs and ears have
covers –> which are green, can photosynthesise
light interception by structures other than leaves: e.gs of plants
- wheat
- barley
- maize
- rice
light interception by structures other than leaves: contributions made by day varies considerably:
- wheat
- barley
- maize
- rice
- wheat: 10-49% (usually > flag leaf )
- Barley: 26-76% (awns that extend form the lemmas of the florets)
- Maize: may be negative
- Rice: 8-23% (flag leaf persists longer, ear bends below canopy)
in wheat, in the first week after anthesis, ear photosynthesis may account for
3/4 of grain growth
