Lecture #14 Temperature

Question 1

optimal growth temp range?

Answer 1

within 10 decrees celsius range

Question 2

What is GDD

Answer 2

heat unit, number of temp degrees above a threshold base temperature for a crop

Question 3

High soil temp effect on roots

Answer 3

increase breakdown and activation of enzymes

imbalance of reaction rates for different processes

Question 4

how can plants survive high temp

Answer 4

with water by maintaining leaves under 45C from evaporative cooling

Question 5

cold soil effects on roots

Answer 5

reduce metabolic activity

decrease water absorption

• increased viscosity
• decrease cell membrane permeability

Question 6

Ice crystal formation and dehydration cause by

Answer 6

cold temp

Question 7

damaged membrane and enzyme caused by

Answer 7

high temp

Question 8

Inhibited photosynthesis caused by

Answer 8

temp stress

Question 9

what can survive higher temps than plants

Answer 9

seeds and pollen

Question 10

why does high temp damage membranes and enzymes

Answer 10

increases fluidity of membrane lipids

decreases hydrogen bond strength

decreases electrostatic relations between polar proteins

alters membrane properties

Question 11

why are photosynthesis and respiration affect at high temp

Answer 11

photosynthesis can’t replace carbon used as substrate for respiration

Question 12

Temp compensation point

Answer 12

the temp where co2 fixed by photosynthesis is equal to co2 released by respiration

when temp exceeds this, carb reserve declines, fruit and veggies lose sweetness

Question 13

effect of freezing

Answer 13

intercellular ice crystals cause physical damage

extracellular ice formation causes dehydration which leads to irreversible membrane damage