Lecture 2 Energy Budgets and structure

Question 1

Heat losses from leaf

Answer 1

“heat radiation emitted” + evaporation (latent heat) the units for it

Question 2

Losses(or gains) at wind

Answer 2

Conduction + convection: sensible heat
(Convection becomes a heat gain if the leaf is cooler than the surrounding air around it.)
Convection: gair(Tleaf-Tair)

Question 3

(Heat losses from leaf) “heat radiation emitted”: e(sigma)Tleaf^4

Answer 3

1. Emissivity, typical value for leave = 0.97
2. constant
3. leaf temperature in Kevin

Question 4

(Heat losses from leaf) evaporation: g leaf* (esat - ea)

Answer 4

1. Leaf total conductance to water vapor (how easy it is for eater to move the inside of the leaf to the atmosphere) related to stomata’s opening, leaf, canopy shape and wind speed
2. Vapor pressure gradient between leaf and air

Question 5

Losses (or gains) Conductance: ~0

Answer 5

loss of heat via diffusion of heat between molecules (mostly in solids and liquids) i.e from leaf down petiole

Question 6

Losses(or gains) Convection: gair * (Tleaf - Tair)

Answer 6

1. Leaf total conductance to heat via convective mixing (how hard it is for heat to move from the inside of the leaf to the atmosphere)
2. The greater the difference in temperature between air and leaf the more convection( Convection becomes a heat gain if the leaf is cooler than the air/becomes negative)

Question 7

Heat gained from the environment

Answer 7

Solar radiation absorbed + “heat” radiation absorbed

Question 8

(Heat gained from environment)abs*

Answer 8

Absorptance (fraction of light hitting leaf that is absorbed)

Question 9

Heat gained from environment: Rsolar

Answer 9

Solar radiation

Question 10

Heat gained from environment: Rheat

Answer 10

Radiation from environment

Question 11

Ways to change leaf (greenhouse etc) energy budget

Answer 11

1. Stomatal opening
2. emissivity (~color such as white
3. Absorptance
4. Wind (Convection and evaporation)
5. Coupling with the atmosphere (convection)
6. Contact with the surfaces(conduction)
7. radiation(thermal or solar)

Question 12

Plant Physiology #1 Leaf

Answer 12

Top to bottom
Cuticle: Top part of the leaf
Epidermis-dermal tissue the second layer of the leaf
palisade mesophyll: ground tissue
(Center) Xylem and phloem -> Vascular tissue
spongy mesophyll -> ground tissue
epidermis

Question 13

Plant Physiology #2 Stem

Answer 13

Outer to inner
Epidermis: ground tissue
cortex and pith (large center) -> ground tissue
Xylem and phloem -> Vascular tissue
Vascular cambium - meristematic

Question 14

Plant Physiology #3

Answer 14

root hair/ epidermis: dermal tissue
cortex(outer)/endodermis (red circle)/ pericycle (inner layer of red circle)
Xylem/phloem