L42: Climate Change

Trend of temperature

Increasing

Rainfall trends

becoming more extreme

What are becoming more common

Climate extremes

Significant climate anomalies and events: March 2020

• Contiguous USA: 10th warmest March on record

• Arctic Sea Ice Extent: 4.2% below 1981-2010 average and the 11th smallest March sea ice extent

• Europe: 6th warmest March on record

• Asia: Temperature departures that were +2.5 degrees or higher. Overall 4th warmest March on record.

• Australia: Above average temperatures during March 2020.

• Antarctic sea ice extent: Near average ending a streak of 41 months of below average monthly sea ice extent

• Caribbean region: March 2020 was 2nd warmest on record

• South America and Argentina: warmest March on record

Growing season timeframe

now 29 days longer compared to the 1980s

What is highly variable

seasonal rainfall:

• winter rainfall is increasing

• summers tend to be drier

trends of winter flooding

frequency and magnitude is increasing

what will weather extremes limit

agricultural income

what do variable weather patterns limit

yield

what did rainfall patterns in 2017 lead to

28% loss of wheat yield

what is happening to global warming

it is accelerating

Consequences of irregular heat stress for plant growth

• reduced photosynthesis

• slower growth due to stress

• impaired germination due to stress

Plant heat stress effects

• Physiological: Pn, Rs and Ci alteration, root respiration enhancement, chlorophyll deterioration, loss of turgarand osmotic adjustment, decreased leaf water potential

• Biochemical: ROS production, accumulation of stress metabolites, reduced photochemical efficiency, increased anti-oxidative enzymes

• Growth and development: Reduction in leaf development and tiller formation, Reduction in plant growth duration, leaf rolling and leaf senescence

• Yield Reduction: Inhibition of seed germination and seedling emergence, poor stand establishment, pollen viability reduction, grain growth and grain quality reduction

What can photosynthesis be modified to do

limit water loss

Why may Photorespiration be an evolutionary relic

RuBisCO first evolved at a time when the atmosphere had far less O₂ and more CO₂

Benefits of photorespiration

limits the damaging products of light reactions that build up in the absence of the Calvin Benson cycle

why does photorespiration limit photosynthesis

competing for RuBisCO

How do dry day plants conserve water

close their stomata- this reduces the supply of CO₂ from the atmosphere

Why does the plant lose carbons in photorespiration

RuBisCO adds O2 instead of CO2 into the Calvin Cycle so the plant loses carbon rather than producing sugars

what can selective breeding do

optimise desired characteristics

How do Artesian hybrids help the corn plant manage water

• Better regulate synchronisation of pollen shed and siking, resulting in successful fertilisation

• Better control of how resources are allocated within the plant, increasing the volume of harvest able per ear.

• Maintain normal growth and development longer into a dry spell

• Optimise growth and health of developing shoot and floral tissues

• Improve water uptake and nutrient uptake through robust root system

Effect of temperature on photosynthesis

Temperature has different effects on different types of photosynthesis

What photosynthetic plants have the broadest temperature range

C₃ but it is lower than that allowed by C₄ photosynthesis

When do CAM plants fix carbon

at night; contributing to the lower optimal temperatures

what inhibits photosynthesis

Higher temperatures

What are many enzymes involved in

Photosynthesis

• crucial enzymes = RuBisCO and RuBisCO Activase

what processes contribute to the inhibition of photosynthesis

• increased photorespiration

• protein denaturation

Relationship between RuBisCo activity and temperature

RuBisCO activity decreases as temperatures icrease

What crops can recover from heat stress quickly

wheat and cotton

Is wheat or cotton more resistant to heat stress

Cotton

Does wheat or cotton have a lower RuBisCO activity in optimal activity

Cotton

Why is cotton more resistant to heat stress than wheat

differences in RuBisCO protein sequence

What is the most abundant protein on the planet

RuBisCO although it is one of the most inefficient

Why is modification of RuBisCO difficult

it has an essential function

what is being used to understand how RuBisCO can be improved

E coli experiments

How is RuBisCO activated

RuBisCO Activase uses ATP to activate it

What enzyme is temperature sensitive

RuBisCO Activase

What are expressed in wheat with different characteristics

2 isoforms

Drought resistant elite lines

• selective breeding

• genetic modification

what is selective breeding reliant on

natural variation

how can genetic modification improve crop yield

constituitive over-expression of selected genes

What do cold signals trigger

Plant life cycle transitions between Stratification and Vernalisation

what is stratification

Stratification in the plant life cycle refers to the process of treating seeds to simulate natural conditions that they must experience before germination. Many seeds, especially those from temperate climates, have dormancy mechanisms that prevent them from sprouting immediately after dispersal. Stratification helps break this dormancy and encourages germination.

Vernalisation

the process by which exposure to prolonged cold temperatures induces flowering in certain plants. This physiological adaptation ensures that plants do not flower prematurely before winter, instead allowing them to bloom in the appropriate season (usually spring)

What does wheat development proceed according to

“degree days”

Wheat growth stages

• Foundation: 6 months, Sowing → start of stem extension, Yield bearing shoots and primary roots form. The canopy is incomplete and light is dull, so growth is slow

• Construction: 2 months, first node → flowering, yield forming leaves, fertile florets, stem reserves and deep roots form. Canopy is complete and light is bright, so growth is fast

• Production: 2 months, post flowering → grains fill and ripen, light is bright but canopy survival and activity depend on good crop protection and ample uptake of nitrogen and water

why do crops now develop faster

global warming

what will the changing climate change

where we can grow our crops

where is coffee usually grown

across South America, Africa and SE Asia

new crop growing locations

maize and wheat cropping is moving North over time due to both positive and negative effects

what could limit irrigation needs

relocating crops

what are some consequences of global warming

• UK and Northern Europe growing seasons will be longer so potentially productivity will increase

• Some regions will be unsuitable for growing crops at commercial sale

• Targeted relocation of crops could mitigate impacts on irrigation, carbon costs and biodiversity

global warming consequences for crop growth

• shifted geographic range

• accelerated growth in some regions

how can we mitigate the negative effects of global warming

• selective breeding

• GM approaches