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College aantekeningen Plant Soil Interactions (5132PLSI6Y)
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SUMMARY PLANT SOIL INTERACTIONS 2023Lecture 1
Plant-Soil Interacti ons in food producti on systems
Franciska de Vries
Interactions: primary/secondary (producers/consumers), symbionts, pollinators, seed
dispersers, predators, parasitoids, seed eaters, endophytes, root feeders, nutrients,
decomposers.
Agriculture caused a shift from hunting/gathering to settling down with farms and
domesticating plants and animals. Agroecosystems extract biomass (crops) which is the most
significant distinction from natural ecosystems (closed cycle).
Earlier agriculture slash and burn.
Modern management Irrigation, adding organic matter, tillage, crop combination and
rotation, selective breeding, ploughing. This allowed human global populations to grow.
Green revolution new farming techonologies like tractors etc. and synthetic fertilizers to
address specific nutrients needs, pesticides for pest control higher crop yields.
Haber-Bosch process converts N2 from the atmosphere into ammonia to be used in mass
production of nitrogen rich fertilizer. Downsides: high energy input and high CO2 emission.
Half of the world population is fed because of fertilizers.
Downsides of these modern techniques:
Greenhouse gasses:
Livestock releases methane. Fertilizers can release nitrous oxide, a powerful greenhouse gas.
Turning forests into fields releases CO2.
Land use:
Nothing else can happen on the agricultural lands. Destroys natural ecosystems.
Freshwater use:
Varies per crop. It makes droughts worse. In spring crops need to germinate, the farmers
pump up groundwater to irrigate when it’s dry, which makes the drought worse. Reduces the
water for other ecosystems and it also causes salinisation.
Eutrophication:
High density of cattle in NL, emits nitrogen in the air. Manure and fertilizer also wash into
the surface water. Global nitrogen cycle is altered because we produce so much of it. Affects
human health. Excess of nitrogen in water creates dead zones, the algae grow and the other
organisms die. Natural ecosystems now have a high availability of nitrogen, this will give
different species and soil acidification which means other nutrients can wash out of the soil.
,Biodiversity:
Farming has wiped out mammal biodiversity. More agricultural space means less space for
wild animals.
Soil degradation:
Happens because of an unsustainable use of land overgrazing (plants will stop growing),
deforestation, pesticides and herbicides (still discovering the effects on soil organisms).
Agriculture also has to deal with problems like climate change. Drought causes crop failure
need for crops that are drought resistant.
Lecture 2
Plant domesti cati on: Crops and their wild ancestors, what happened in between?
Pamela Strazzer
History of agriculture
Agriculture started around 13.000 years ago in the middle east. Fertile Crescent fertile
soil and favourable conditions for agriculture. Fast growing plants, because the plants didn’t
struggle to look for nutrients.
It started there because of the availability of suitable wild plants for domestication/stable
climate/access to water sources.
It then spread in Eurasia, in regions with a consistent climate zone (seeds could be
transported and still germinate, because the conditions were equal).
People chose plants with a specific phenotype that suited their needs best, and in doing this
repeatedly they made a genetic selection which caused the plants to look very different over
time than their original ancestor. The genotype changed.
Social surplus – Agriculture made it possible to have enough food to also feed people around
you. People released from searching food had time for other things, like art and science.
Among the first cultivated plants were wild barley, wild einkorn, and wild wheat.
These plants were domesticated by early farmers, leading to the emergence of agriculture.
Domestication involved selecting and cultivating plants with desirable traits, such as higher
yields and suitability for cultivation.
Domestication
Qualities Needed for Domestication in Animals:
Docility: Domesticated animals should be relatively calm and not prone to aggressive
behavior towards humans or other animals.
Social Behavior: They should not be excessively fearful of each other, making it easier to
keep them in groups or herds.
,Breeding Behavior: Animals should have a willingness to breed in captivity without any
inhibition or difficulty.
Rapid Growth: Domesticated species are often preferred if they exhibit rapid growth,
making them more economically viable for food or other purposes.
Recognition of Humans: They should have the ability to recognize humans as leaders or
providers, which aids in their management and care.
less than 500 species are domesticated.
Qualities Needed for Domestication in Plants:
Genetic Variability: Domesticated plants should exhibit genetic diversity, allowing for
selective breeding to enhance desirable traits.
Morphological Potential: They should possess morphological characteristics such as size,
shape, or fruit type that are beneficial or preferred for human use.
Linkage of Domestication Genes: Certain genetic factors may be linked to domestication
traits, making them easier to select for and propagate.
Non-Toxicity: Domesticated plants should not contain toxic compounds in quantities that
would be harmful to humans or other animals.
Loss of Seed Dispersal: Domesticated plants often lose the trait of natural seed dispersal,
making it easier for humans to collect and harvest the seeds. Beans used to open and let all
the seeds fall out, if they were kept inside in nature this would just let the seeds rot, but our
version keeps them inside so they can be collected.
Changes in Plants After Domestication:
Increased Size: Domesticated plants tend to exhibit an increase in the size of inflorescence
(flowers), fruits, and grains. For example, teosinte evolved into maize.
Loss of Seed Dispersal: Domesticated plants lose their natural seed dispersal mechanisms.
For agricultural purposes, it's more convenient to have seeds that are easily collected.
Reduced Branching: To maximize space and yield, domesticated plants often exhibit
reduced branching, resulting in a more compact growth habit.
Gigantism: Domesticated plants produce larger fruits and seeds, making them more suitable
for human consumption.
Increase in Phenotypic Diversity: There is an increase in visible differences among
domesticated plants due to selective breeding, even as genetic diversity decreases.
Reduction in Toxic Compounds: Domesticated plants often have fewer toxic compounds
compared to their wild counterparts.
Reduction or Elimination of Seed Dormancy: Domesticated plants tend to lose the trait of
seed dormancy, allowing them to germinate more readily. Seed dormancy means the seeds
would not germinate until there were perfect circumstances.
Ability for Vegetative Reproduction: Some domesticated plants can reproduce
vegetatively, such as through cuttings or grafting, facilitating propagation. For example in
fruit trees, to get exactly the same DNA in the tree. Used with a popular grape plant for a
specific wine.
Flowering Chances: Domesticated plants may be bred to be insensitive to day length,
ensuring consistent flowering and fruiting under various conditions.
Changed Interaction with the Environment: The domestication process alters the way
plants interact with their environment, as they are cultivated for human purposes and may
rely on human care for survival.
Domestication as a process is fast evolution. Selective pressure is given by people, strong
artificial selection.
, Evolution
Mutations in heritable cells contribute to evolution.
These genetic inheritable mutations occur by chance. They are the material on which
selection acts. Mutants can have a better or worse fitness (performance) and will have a better
or worse chance for a large progeny.
Fixation of the mutation – change in the genetic composition of the population.
Theory of Evolution by Darwin and Wallace.
Two species can get separated from each other and evolve in different selective pressures and
will become two different species and can’t mate anymore. = speciation by isolation.
In flowers it can also be because they have different pollinators. But humans might be able to
hybridize by cross pollination.
All dogs come from a single ancestor. from Canis Lupus to Canis Lupus Familiaris.
Only a few genes changed can lead to dramatic changes.
There are big differences in dog races.
Humans and dogs have lived together for 30.000 years.
Dogs with short vs long legs 1 single mutation in s FGFR3. Growth hormone receptor.
Mutation in BMP3 growth of different body parts is not allometric/not in proportion.
BMP3 (bone morphogenetic protein) is a regulator of skeletal growth. Transcription factor.
Crops have larger fruits
In tomato this is a mutation in two genes:
- Fw2-2 : cell cycle control (more cells per fruit)
- Fas (YABBI) : organ number (more lobs per fruit)
Maize
Genetics behind the acquisition of a naked ear
1 mutation in Tga (= a regulator of gene expression). Results in amino acid change. Leads to
exposure of seed.
Regulatory genes are genes that control the expression of many other genes. They often
encode for transcription factors.
Genes Determining Petunia Flower Color:
In petunias, the color of the flowers is determined by a complex interplay of genes, with
AN1, JAF13, AN2/AN4, and AN11 playing pivotal roles.
These genes are often referred to as transcription factors because they have the unique ability
to switch on entire genetic pathways responsible for the production of pigments in petunia
flowers.
Collectively, AN1, JAF13, AN2/AN4, and AN11 represent a network of transcription
factors that activate or inhibit specific genes involved in pigmentation pathways.
By toggling these genetic switches, petunias can produce a stunning array of flower colors,
allowing for a rich diversity of petunia cultivars enjoyed in gardens worldwide.
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