Physiology of Yield

Question 1

What affects productivity?

Answer 1

Plant architecture
Photosynthesis
Partitioning
To improve plants, put more energy in (nutrients, light interception and photosynthesis) and make energy use more efficient (partitioning)

Question 2

Light interception

Answer 2

Light changes on time scales and in angle
Different paths and intensities depending on season and time of day
Scattering - direct, reflected, refracted/diffused
Direct = peak in blue
Diffuse = peak in red (wavelength increased when refracted)

Question 3

Leaf morphology

Answer 3

Leaf size - larger = more area for photosynthesis = more energy and water to make cells
Leaf shape - long & narrow = reduced transport; indentations = reduce wind and water damage
Colour - depends on chlorophyll and other pigments; red and blue absorbed higher in canopy, far red travels further; green absorbed poorly
Leaf area index - total one sided green leaf area per unit ground surface; determines light interception, photosynthetic rate and evapotranspiration

Question 4

Leaf movement

Answer 4

Heliotropic - moves in response to sun to maintain best angle for leaf exposure to sun

Question 5

Leaf angle

Answer 5

How much energy can hit leaf area (high light = more erect)
Erectophile - >30deg; high light
Plagiophile - 30-60deg
Planophile - <60deg; low light

Question 6

Canopy/community structure

Answer 6

Self shaded leaves - lower leaves get very little light so avoided in low light env (okay in high light); dense crops increases self shading
Insulating effect - warmer at bottom
More red/far red at bottom
Leaves at bottom more inefficient

Question 7

Crop duration

Answer 7

Leaf and flower early to maximise energy into grains
Late senescence so more time for this