Sogbon Tope

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Plant signaling

• 
  sogbon .s.tope

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What is plant signaling

• Plant signaling involves the conveying of
  information within and between plant cells from
  receptor systems to effectors.
• signals can take many forms, including chemical
  and electrical.
• signaling can occur locally within a single plant
  or between different plants, including plants of
  different species.

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signals

• Signals are generally considered to be an
  intended information broadcast and can includes
• hormones,
• bacterial,
• metabolites,
• electrical,
• light quality and
• stress signals etc

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Types of signaling

• Internal signaling

• External signaling

• Primary metabolites
• Hormones ( chemical )
• Electrical pulses

• Environmental factors
• Atmospheric
• Edaphic
• Light
• Biotic

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Stages of signaling pathways

• reception

• transduction

• response

• Receive a response to a stimulus.
• -Phytochrome
• -photoreceptor
• -Located in cytoplasm

• - Use of second messenger
• ( amplifies the signal ).
• - Calcium ions cyclic GMP
• ( both have to be for a complete etiolation).

• Regulate one or more cellular activities (
  usually increased response of an enzyme ).
• Post translation modification or
  transcriptional.

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response

• Post translational modification
• - Usually modified by phosphorylation of
  amino acids.
• -Protein kinases.
• -Protein kinase phosphatase turn off the
  initial signal.

• Transcriptional regulation
• - Bind directly to the DNA.
• - Activated by kinases.
• - Can be either activators or
  repressors.

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Receptor classes
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example of plant signaling

• Etiolation
• - Plant adaptions for growing in the dark
• - Pales stem, unexpanded leaves short roots.
• De etiolation ( greening )
• Stem elongates.
• Leaves expand.-
• Roots elongate
• - Shoot produces chlorophyll

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Primary Metabolites

• Primary metabolites are compounds that are
  commonly produced by all plants and that are
  directly used in plant growth and development.
• The main primary metabolites are carbohydrates,
  proteins, nucleic acids, and lipids.

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Plant Hormones

• Hormones are chemical signals that coordinate
  different parts of an organism.
• Plant hormones are produced in very low
  concentration, but a minute amount can greatly
  affect growth and development of a plant organ.
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Some hormones and their functions

• Auxin
• The term auxin refers to any chemical that
  promotes elongation of coleoptiles
• Stimulates stem elongation.
• Promotes the formation of lateral and
  adventitious roots
• Regulates development of fruit
• Enhances apical dominance
• Functions in photo-tropism and gravitropism
• Promotes vascular differentiation
• retards leaf abscission.

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Cytokinin

• Regulate cell division in shoots and roots
• Modify apical dominance and promote lateral bud
  growth
• Promote movement of nutrients into sink tissues
• Stimulate seed germination
• Anti aging effect.
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Gibberellins

• Stimulate stem elongation,
• pollen development,
• pollen tube growth,
• fruit growth,
• seed development and germination

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• Gibberellin-induced stem growth
  Gibberellin-induced fruit growth
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Brassinosteroids 

• Promote cell expansion and cell division in
  shoots
• Promote root growth at low concentrations
• Inhibit root growth at high concentrations
• Promote xylem differentiation and inhibit phloem
  differentiation
• Promote seed germination and pollen tube
  elongation

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Ethylene

• Promotes ripening of many types of fruit,
• Leaf abscission,
• Inhibition of stem elongation,
• Promotion of lateral expansion, and horizontal
  growth
• Enhances the rate of senescence
• Promotes root and root hair formation
• Promotes flowering in the pineapple family,

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tropism

• Any response resulting in curvature of organs
  toward or away from a stimulus is called a
  tropism
• Tropisms are often caused by hormones.
• Plant tropisms are mechanisms by which plants
  adapt to environmental changes.

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Phototropism ( light responses )

• Phototropism is the directional growth of an
  organism in response to light.
• Photoreceptors in plant cell detect light, and
  plant hormones, such as auxins, are directed to
  the side of the stem that is furthers from the
  light.

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Types of photoreceptor

• phytochrome

• Blue - light

• These receptor absorb mostly blue
• May be responsible for opening stomata.
• Inhibit hypocotyl.
• Elongation in seedlings

• These receptors absorb mostly red light.
• Responsible for de etiolation.
• Seed germination and avoid shade

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gravitropism

• Gravitropism is growth in response to gravity.
• Roots show positive gravitropism shoots show
  negative gravitropism

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Thigmotropism

• Thigmotropism describes plant growth in response
  to touch or contact with a solid object.
• Rapid leaf movements in response to mechanical
  stimulation are examples of transmission of
  electrical impulses called action potentials

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Stress signals

• Environmental stresses have a potentially adverse
  effect on survival, growth, and reproduction
• Stresses can be abiotic (nonliving) or biotic
  (living)
• Abiotic stresses include drought, flooding, salt
  stress, heat stress, and cold stress

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Thanks for attention