PLANT DEVELOPMENT AND BIOTECHNOLOGY

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1 Δεκ 2012 (πριν από 5 χρόνια και 1 μήνα)

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PLANT DEVELOPMENT AND BIOTECHNOLOGY


Plants and animals different in development:

Consequences of differences of life style

Animals heterotrophic and mobile,

Plants photoautotrophs and sessile

Animals use motility to respond to external environment

Animal
s use growth to respond to external environment

Animals live with limits of hydration in cells


water

No cell wall

Plants must vary dramatically in water contents, due to availability

Cell wall


Differences in development:


COMPARE TO ANIMAL DEVELOPMENT

Animal cells & embryos:


No cell walls


Cells move


Cell to cell recognition


dorsi
-
ventral anterior posterior


symmetry


determinant development

Plant Cells:


Cell walls


Cells stay in relationship


To neighbor
s


Cell cytoplasm connected


radial symmetry


indeterminant development,


maintain meristems


some commonality in developmental

controls:

signal transduction pathways

cell trafficking

signal/control networks


use of mutants and

model systems

sea urchin

fruit fly

mouse, etc

plant:
Arabidopsis


review reproduction again


Start with fertilized egg to adult plant

Look at controls on development

Development = growth, partly responses

to environment

Zygote (in embryo sac) to embry
o

(heart
-
shaped

then torpedo
-
shaped) finally in seed 37.2 (742
-
43)


embryo endosperm and seed

monocot vs. eudicot


Meristems: shoot: plumule, root: radicle (at tips) 35.6 (732)


shoot apical meristem



leaf primordia



lateral buds



branches i
n order from lateral


buds


root apical meristem




root hairs




lateral roots in little order

presence of dividing cells

(meristems) throughout plant

for growth responses to

environment




Stems:

Leaves and branches

Leaf Primordia



leaves

Axillary buds


lateral branches


Precise locations

Leaf position: alternate, opposite, whorled

Plant architecture


Roots:

Root cap and meristem

Lateral roots from within, irregular


Plant tissues:

Epidermis

Cortex

Vascular bundle

Xylem


vesse
l elements

Phloem


sieve tube elements & companion cells

Parenchyma

Collenchyma

sclerenchyma



Primary and secondary growth

Vascular bundles


cambium


Secondary growth in palms

Diffuse vascular bundles


Induction of Flowering

Environmental controls:

as
photoperiod & temperature changes, or moisture


phytochrome: red (Pr) and far
-
red (Pfr) forms



Roles of Growth Regulators

(hormones) in controlling

Development


Signal

Sensory organ

Signal transduction:





Gene transcription




Gene translation





Cell division





Cell expansion


Cell differentiation, etc.





Auxin (indoleacetic acid)

Promotes cell elongation

Tropisms (growth orientation)

Root growth& other


Cytokinins promote cell

Division and differentiation

41.27 p. 820


Gibberellins

promote germination

And growth

p.820 p. 753 37.17


Absciscic Acid promotes

Senescence, as in leaf

Dehiscence


Ethylene promotes ripening

And senescence

And plant defenses


Plant Development and Biotechnology


Totipotency realized:

One cell


adult orga
nism




New crops:

Herbicide resistance

Bt toxin kills larval insects

Better nutrition (vitamin a in rice)

Pharmaceuticals from plants


Major GM crops:

Maize (corn) 80% of US crop now

Canola

Cotton

Soybean


Dangers and Socio
-
political considerations



Shortage of Doritos


consumer awareness

Health effects


allergies?

European and other acceptance

--

transparency
?

Escaped weeds

and genes


Who benefits? companies or the poor, or both?