AGR2451 Lecture 16:

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AGR2451 Lecture 16 The Past and Future of
Agriculture Mid-term Exam 1-220pm Tues,
November 12th Last name A-K Room Richards
124 Last name N-Z Room Richards 022 No
reading this week. Review of the last lecture
1. What is a plant? (Review) These last 16
lectures have been about trying to build a plant
as evolution did from the Primordial Soup. So,
3 billion years later, what is a plant and why is
it useful for animals and humans
(agriculture)? Life is a series of biochemical
reactions that gather or metabolize nutrients
(C, N, O, P, S, etc.) into macromolecules. Life
organizes biochemistry by switching on/off genes
that encode enzymes or structural proteins to
create organelles, cell types, organs, or
environmental responses. Whereas animals are
mobile and heterotrophic, fungi are immobile and
heterotrophic, plants are immobile and
autotrophic. What are the implications of this
strategy? (for you to think about) A plant body
is nothing but a nutrient-gathering machine
From Plants, Genes and Agriculture, page 460 M.
Chrispeels and D. Sadava (1994) Jones and
Bartlett Publishers, Boston, MA
Slide 16.1
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1. What is a plant (continued) A plant gathers
nutrients to build complex molecules to build
organized structures. Why? to propagate its own
DNA How? as it senesces (annuals) or perennials,
it transfers nutrients from its vegetative
structures to ensure the survival of its progeny
DNA. Flowering plants developed seeds and
fruits. Thus, the plant vegetative body is both
a nutrient-gathering machine and a
nutrient-storage machine connected to its
reproductive structures. Because a plant is
immobile, it substitutes shunting of primary
metabolism (abiotic stress) and production of
secondary metabolites (biotic interactions) for
animal behaviour. Secondary metabolites allow a
plant to communicate with its environment
(signals to attract Nitrogen-reducing bacteria,
pollinators..). Because a plant is a rich
source of nutrients and immobile, it must invest
a lot of its resources to fighting pathogens.
Slide 16.2
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2. How did the last 10,000 years and the Green
Revolution improve plants for human use?
(Review) selection against secondary metabolites
(pesticides) in grains (seeds) and other storage
tissues if used for silage, then selection
against pesticides in leaves.
Implications? effect on flowering photoperiod?
early maturation shorter growing season
(related to flowering) change in C/N allocation.
How? selection against seed shattering
(against natural seed dispersal) pest and
disease resistance abiotic stress
resistance delayed senescence of photosynthesis
during grain-fill or fruit-fill
period selection against indeterminate growth.
What is it and why? selection against seed
dormancy requirements selection against
allelopathy this may have contributed to our
enhanced need for herbicides (?) selection for
enhanced nutrient quantity and quality (starch,
protein, oils) and vitamins in storage
organs semidwarf varieties why? farming
practices towards monocultures, irrrgation, NPK
fertilizers, pesticides, herbicides loss of
genetic diversity use of machinery, decline in
labour, use of larger farms change from more
sustainable farming practices. sudden change
caused the displacement of farmers, women
and traditional knowledge
Slide 16.3
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2. The Last 10,000 Years of Agriculture
(continued) much higher food production without
increased land use the prevention of mass
starvation. What has caused the surge in human
population in the last 60 years?
From Plants, Genes and Agriculture, page 15 M.
Chrispeels and D. Sadava (1994) Jones and
Bartlett Publishers, Boston, MA
in the last 30 years, the yields have doubled
From Plants, Genes and Agriculture, page 307 M.
Chrispeels and D. Sadava (1994) Jones and
Bartlett Publishers, Boston, MA
Slide 16.4
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3. What must the next Green Revolution do? 3A.
GOALS 1. We must produce more food in the next
50 years than in the entire history of humanity.
Why? a) b)
2. Biggest concerns? a)Freshwater b)Global
warming
From Plants, Genes and Agriculture, page 40 M.
Chrispeels and D. Sadava (1994) Jones and
Bartlett Publishers, Boston, MA
c)Marginal lands
From Plants, Genes and Agriculture, page 440 M.
Chrispeels and D. Sadava (1994) Jones and
Bartlett Publishers, Boston, MA
3.Need for Sustainability -food production -basis
of renewable-resource manufacturing, polymers,
medicines, etc. 4. Need Enhanced profits for
farmers.
Slide 16.5
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3B. HOW? What are the CURRENT LIMITATIONS for
plants as a nutrient-gathering machine for
humans? Premise Agricultural plants are nutrient
gathering and storage machines. As they
senesce, they transfer nutrients to their
reproductive structures. a)Rubisco. What are the
2 problems? Consequences?
Solution? b)Nitrogenase What is the
problem? What is the solution? c)Rhizosphere
Plants give up to 30 of their fixed carbon to
the Rhizosphere. Why? d)Plants
senesce (stop photosynthesis) as grain-fill
begins. How can this be overcome? e)Ratio of
C/N allocation to vegetative structures vs.
harvest tissues. f)Inability to use saltwater as
a consequence of plant evolution onto
land. g)Cellulose cell walls. This prevents
humans from directly eating leaves. h)Abiotic
stress tolerance drought, cold, heat, salt to
overcome yearly variations. How? i)Biotic
stress tolerance and develop a way to prevent
resistance j)Hybrid vigor Determine what causes
it and how to sustain it beyond the F1
generation. k)Using other crops. Creating new
crops (hybrids) by breaking species barriers
this has been the basis of land plant evolution.
How? L)We need a better understanding of the
biology of crops that store their carbon as
underground storage tubers (cassava, sweet
potatoes, yams).
Slide 16.6
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3. Limitations to Agriculture (continued) We
need to overcome these limitations and combine
them with sustainable farming practices.
Sustainable farming preserves the environment
without an ideology of how to do this nothing
is necessarily excluded (unlike in Organic
Agriculture) I)crop rotations implications
for pests/disese and Nitrogen II)green manures
plow forage legumes (alfalfa, clover,etc.) into
soil III)conservation tillage/no tillage
mechanisms to preserve ground cover to prevent
soil evaporation and prevent soil
erosion IV)Integrated Pest Management use
natural enemies of pests, resistant plants and
good crop management, use pesticidse at most
effective times V)genetic diversity multiple
genotypes of one species or multiple species
resistance against disease/pests roots that
extend to different heights to make better use
of soil nutrients and moisture. CaviatsAll of
the above is in the world of Biology in the real
world, there are many more pressing issues for
agriculture like poor infrastructure, trade
policies, access to technology, access to loans
to buy technology, government subsidies and
unfair trade practices poor education for
women, corrupt governments and war.
Slide 16.7
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4. Curent and Future Techniques for Crop Gene
Improvement a)Breeding Breeders select for the
final phenotype by selecting for multiple
mutations at multiple genes at once Breeders
select for subtle mutations, whereas
geneticists/molecular biologists select for
extreme mutants Breeding is slow.
From Plants, Genes and Agriculture, page 340 M.
Chrispeels and D. Sadava (1994) Jones and
Bartlett Publishers, Boston, MA
during the last 20 years, the time required to
introgress and select for the trait of interest
has been decreased by gt50 by marker-assisted
selection. What is the principle behind this
and how does it work?
On board
Slide 16.8
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b)Molecular Biology the use of
Transgenes selection for genes, then determine
the phenotype the key advantage is that
transgenes can break the species
barrier Examples? Golden rice - high iron
and vitamin A (beta-carotene) into rice endosperm
using transgenes -120 million children are VitA
deficient -1-2 million deaths -Golden Rice 10
of daily requirements (so far)
From Plants, Genes and Agriculture, page 106 M.
Chrispeels and D. Sadava (1994) Jones and
Bartlett Publishers, Boston, MA
Vitamin A carotenoid derived from isoprene
metabolism
Ye et al. (2000) Engineering the ProvitaminA
(beta- carotene) biosynthetic pathway into
(carotenoid free) rice endosperm. Science 287,
303-306. AAAS Publishing, Washington, D.C.
Slide 16.9
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Other traits in progress by molecular
engineering naturally decaffeinated coffee!!
From Plants, Genes and Agriculture, page 406 M.
Chrispeels and D. Sadava (1994) Jones and
Bartlett Publishers, Boston, MA
c) Emerging techniques Chimeroplasty?
Medicines for plants? Bioinformatics? Gene
chips and protein chips
Slide 16.10
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.What will Agriculture look like in 20-30
years?? enhanced C/N/H20-use efficiencies for
food production enhanced abiotic and biotic
stress tolerance plants as fuel cells plants as
the basis of carbon-based fuels (ethanol) plants
for industrial use polymers DuPont creating
nylon fibres from corn phytoremediation -
using plants to clean up environmental
toxins plants as factories of vaccines, vitamins
and nutrients for human health (nutraceuticals)
THE SKY IS THE LIMIT!!! .Final
Comments perhaps only 1 is known about the
biology of plants!! knowledge is the power to
change and make a practical difference, not
ignorant protest plant research is a race
against time (30-50 years)