• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6
  7. 7
  8. 8
  9. 9
  10. 10
  11. 11
  12. 12
  13. 13
  14. 14
  15. 15
  16. 16
  17. 17
  18. 18

Induced defence responses against herbivores. The aim of the project was to study the effects of jasmonic acid, one of the plant hormones involved in induced plant responses, when applied to tomato seeds before they are sown

Extracts from this document...


´╗┐Induced Defence Responses Against Herbivores I. Introduction The aim of the project was to study the effects of jasmonic acid, one of the plant hormones involved in induced plant responses, when applied to tomato seeds before they are sown with a view to the effects initiating a positive effect and induced responses being ?switched? on constantly. Over the years, studies have shown that many plants, both wild and agricultural have the ability induce responses to herbivore damage, induced damages being those which are demonstrated after a herbivore attack has taken place (Constable et al., 1996). In many plants, the responses are regulated in time and space by a highly complex regulatory networks, (M. R. Roberts et al., 2001) which in turn are modulated by interactions with other signalling pathways. The key signalling hormones which will be discussed are jasmonic acid (JA), ethylene, asbscic acid (ABA) and salicyclic acid (SA) along with the roles which ion fluxes, protein phosphorylation cascades and active oxygen species play in the inducement of defence responses against herbivore wounding. The responses both in individual leaves and systemically, over the unwounded areas of the plants will also be discussed. II. Response Overview When herbivore damage is sustained, the immediate surrounding areas around the wound will consist of different populations of cells. The wound site will consist of damaged cells which are beyond repair but which may also provide a key role in the initiation of an induced response as they will release signalling molecules which can act as elicitors of responses in the neighbouring intact cells or will act as defensive toxins which can cause damage or kill the attacking organism. ...read more.


The remaining eight mutants defined four loci, two of which were insensitive to systemin and lacked systemic wound response. The results confirmed the theory that prosystemin and systemin are both functional in the transduction of systemic induced resistance in the tomato plants and that wound expression is induced in 3 genes, Def-1, Spr-1 and Spr-2 (those insensitive to systemin) by the actions if wounding, systemin and 35S::prosys. Thaler in 1999 investigated the effects of JA as a natural elicitor to induce resistance to herbivores. Here, she applied jasmonic acid to the foliar regions of the plant and found that the application of JA increased levels of polyphenol oxidase. The plants which were induced received 60% less leaf damage than the control plants. Thaler also observed that although the plants which were treated produced less flowers, the fruit yield from the crop between the treatments. She also was that there was no difference between the yields of the induced plants and of the control plants under both natural control conditions and under reduced herbivore levels. Thaler concluded that the fact that there were no differences in yield was due to the low levels of herbivory experienced by the plants and that JA treatment produces a natural herbivore resistance at no cost to the tomato or its yield and this treatment could be of high value in agriculture, reducing the use of man-made pesticides, providing a cheap, natural alternative. Figure 2. This figure, taken from Thaler, (1999) ...read more.


The studies have shown that elicitors and wounding cause a rapid depolarisation in the plasma membranes electrical potential, driven by an efflux of K+, an influx of protons and the alkalinisation of the extracellular medium surrounding the wound site. When chemical agents which disrupt the fluxes are applied to the cells, a disruption of defence gene expression can be seen. An example by Messiaen in 1999 showed that when fusicoccin, a fungal toxin was applied, H+-ATPase was activated in the plasma membrane and the membrane becomes hyperpolarised, inhibiting the expression of the gene which expresses systemic wound inducement and glycan synthesis. In 1999 it was also shown by Schaller and Oecking that some wound response genes were activated with the application of, H+-ATPase inhibitors when there is no other wound/elicitor induced stimulus present. Calcium ions also play a casual role in the wound signalling pathway. Knight et al., 1993 gave evidence to show that following wounding there is a rapid increase in cytoplasmic Ca2+ concentrations, and when calcium channel blockers are applied to a wound site, and molecules which cause the mobilisation of intracellular Ca2+ stores, elicitor induced gene expression has been seen (Leon et al., 1998) The induced defence mechanisms of a plant are complex, with many signalling pathways and molecules involved in the inducement of defence genes, including various ions, plant hormones and even mutant genes. But most notably the effects of jasmonic acid when applied both externally or induced internally must be taken into account, as this, most studies show is the mainstay of induced plant defence mechanisms. IV. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our University Degree Botany section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related University Degree Botany essays

  1. Marked by a teacher

    Drought conditions, low and high temperatures, increased salt levels, pathogens and insects are common ...

    3 star(s)

    Plants have evolved to combat salt stress on three levels. Firstly, there are halophytes, plants which are tolerant to salt but do not grow in highly saline conditions. There are then glycophytes, which can tolerate salt, but not to the extent of halophytes. Finally there are euhalophytes, or true halophytes.

  2. To investigate the effects of abiotic factors specifically pH on the abundance of marram ...

    Use a pH key with a higher level of sub-divisions. This would allow more accurate observations of colour change to be made. The changes of colour between samples at a pH of 5.5 and 6.0 could be clearer to observer allowing a more conclusive result.

  1. An investigation to find the effect of bile salts on the digestion of fats.

    I will use the same batch of milk, bile salts, lipase and sodium carbonate for each bile salt concentration. The concentration of bile salts for each triplicate of one concentration. So that the same amount of bile will be working on the emulsification of fats and the experiment will be

  2. Work shope on plant Cryopreservation

    Safety measures during cryopreservation: There is certain safety measures associated with the use of liquid nitrogen. There is a risk of suffocation with the use of liquid nitrogen. To avoid this liquid nitrogen must be used in a proper ventilated room. The storage Dewar's must be ventilated to prevent explosion.

  1. Fostering Local Sustainable Agriculture

    The effectiveness of local government planning programmes in dealing with agricultural issues has been varied. The value of agriculture to the community's overall well-being has not always been understood or recognized and has, at times, been reflected in local decision-making.

  2. To what extent does plasticity of dipterocarp seedlings affect growth and survival in the ...

    and chlorophyll content was measured for each leaf. Average SLA and chlorophyll content was calculated for each seedling using this data. The percentage herbivory was also estimated for each of the selected branches. This was calculated by counting the number of leaves on the branch, recording the number showing herbivory and estimating the herbivory damage shown on each leaf.

  1. A review of the development, production and post harvest requirements of Gerberas

    3.3 Cultivation in substrates: There are many advantages of growing Gerberas in substrates rather than soil, and the main factor is that the crop is easier to control and manage. Plants are grown in pots of the substrate on bench systems (figure 3), which allows the working height to be determined.

  2. Mechanisms of insect resistance induced by treatment of Lycopersicon esculentum seeds by jasmonic ...

    For example, microbial pathogens such as Agrobacterium tumefaciens which causes crown gall disease, may enter at and attack the wound site, which has resulted in the evolution of a complex system of defence against both the herbivores and pathogens. The responses are almost always induced responses and the response pathways are directly activated as a result of herbivore wounding.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work