Samenvatting
Summary Sammenvatting Seed Science and Techology (PPH31306)
Complete samenvatting van het vak Seed Science and Technology: alle lectures, powerpoints en bijbehorende hoofdstukken uit het boek Seeds.
[Meer zien]Voorbeeld 4 van de 51 pagina's
Voorbeeld 4 van de 51 pagina's
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Seed science and technologyLecture 1 Introduction chapter 1
Importance of seeds
• Seeds are a major food source: ~ 90% of the annual worldwide seed production
contributes to 50% of the energy intake. The Netherlands are number 1 seed
exporting country.
• Seeds preserve natural environments (biodiversity): soil seed banks determine next
generation vegetation. Some species are endangered by climate change. In gene banks
seeds are safeguarded. The seed bank Svalbard in Norway has copies of all accessions
from other seed banks worldwide. Here seeds are stored under controlled conditions
in the permafrost and can be used to replant destroyed areas.
Lecture 2 What is a seed?
Seeds form the next generation of a plant, containing a complete new generation (the
embryo), as well as other supportive (endosperm, perisperm or cotyledons for angiosperms
and megagametophyte for gymnosperms) and protective (seed coat) structures.
Seeds are products of fertilization between pollen and egg. Pollen and egg are produced by
seedplants: in the flowers of angiosperms and in the cones of gymnosperms.
Angiosperms can be either monocots or dicots
Seed structures: the different tissues of a seed
Embryo: next generation of the plant, formed by fertilization of the egg cell nucleus in the
embryo by one of the male pollen tube nuclei, that is ♀♂
Endosperm: nutritional tissue, arises from the fusion of two polar nuclei of the central cell in
the embryo sac with the other pollen tube nucleus, thus ♀♀♂
Seed coat: protective tissue, also called the testa, derived from the integument(s) around the
ovule and thus ♀♀
.
Funiculus: the umbilical cord, structure that joined the seed to its parent plant
Hilum: scar marking the point at which the seed was joined to the funiculus
Micropyle: a small depression at one end of the hilum (not present in all seed coats)
,Different seeds have different seed structures
True seeds: do not contain the maternal pericarp tissue: legumes, cotton, tomato, squashes,
coffee bean produces true seeds.
Fruits are seeds without a (complete) seed coat but with a pericarp: cereals, lettuce,
sunflower, nuts, buttercup, anemone.
,Seed reserves
-Storage reserves: Carbohydrates, oils and proteins
-Others: Alkaloids, lectins, proteinase inhibitors, phytin and raffinose family
oligosaccharides (RFOs)
Average percentages storage composition and location differ between different crop species.
Protein Oil Carbohydrate Major storage location
Cereals 11 5 84 Endosperm
Legumes 29 8 53 Cotyledons
Agricultural revolution(s)
Seeds are (at) the basis of the agricultural system. (Starting material & end product).
1. During the First Agricultural Revolution/ Neolithic Revolution (circa 10 000 BC),
the prehistoric transition from hunting and gathering to settled agricultural took
place.
2. The Second Agricultural Revolution/ British Agricultural Revolution (17th – 19th
century) involved the introduction of new crop rotation techniques and selective
breeding of livestock, resulting in a marked increase in agricultural production.
3. The Third Agricultural Revolution/ Green Revolution (1930 - 1960) concerns an
increase in agricultural production as a consequence of irrigation, specialized seeds,
machinery, fertilizers and pesticides. Especially took place in the developing world.
Domestication: the initiation of the process of evolutionary divergence from wild ancestral
species. For examples wheat, maize and rice.
Diversification: the subsequent evolution of new varieties, including greater improvement
in yield, adaptation or quality in crop species.
Commonly observed traits in crops after domestication (1) and diversification 2-4):
Stage 1 Stage 2 Stage 3 Stage 4
Larger seeds More seeds Reduced Increased yield
vernalization
Resource allocation Pigment Reduced photoperiod Increased abiotic
variation sensitivity stress tolerance
Thinner seed coat, Increased seed Modified hormone Increased biotic
increased seed-softening size variation sensitivity stress tolerance
and ornamentation
Inflorescence architecture Flavour change Synchronized Improved eating
(shape, number, flowering time quality
determinacy )
Increased yield potential Change in Shortened or
and productivity starch content extended life cycle
Loss of dormancy Reduced Dwarfism
germination
inhibition
Determinate growth Non-shattering
seeds
, In different crops, different natural mutations in the same genes were selected for the case of
non-shattering and plant architecture.
Seeds as populations
Dormancy release or germination of seeds are binary responses: either a seed germinates or
not.
Relation between such responses and abiotic factors are represented in a Sigmoid curve like
the one below. This behaviour is called ‘Threshold’ behaviour in which a certain abiotic
factor needs to be exceed before a process occurs. As individual seeds vary in their
sensitivity to temperature, light, moisture, often over a logarithmic concentration range the
Sigmoid curve represents the relationship between the response (germination) percentage
over time.
Population-based-threshold (PBT) models are useful in describing the duality of individual
diversity (each seed relies on its own resources to persist, germinate and grow into a
seedling) and population-wide-behaviour (the percentage of seeds in a population that is in
an particular state). As thresholds may be different for individual seeds, , population based
models capture variability by averaging.
ΘX = (X – Xb(i))ti
ΘX = the time constant for responses to factor X
X = the dosage level of factor X
Xb(i) = the sensitivity threshold distribution of the population for a given phenotype or
response
Ti = the time at which fraction i of the population exhibits the phenotype or response due to
factor level X
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