The effects of the Abiotic factors on plant herbivory interactions

3rd Discussion session

Plant-Insect Interaction Course

• Herbivory: The consumption of herbaceous vegetation

• Herbivores: An animal that feeds chiefly on plants.

• Herbivorous: Feeding on plants; plant-eating.

• .Herbivorous - feeding only on plants• Carnivorous - (used of plants as well as

animals) feeding on animals; "carnivorous plants are capable of trapping and digesting small animals especially insects“

• Insectivorous - (of animals and plants) feeding on insects

• Omnivorous - feeding on both plants and animals

• Plants are static organisms and cannot escape the pressure caused by biotic and abiotic factors. They must increase fitness and prepare adequate responses to external stimuli.

Plants talk, but are they deaf

Marcel Dicke et al.

Humans often consider plants to be passive organisms, even though individual plants display directed responses to resources such as light and nutrients.

Plants ‘talk’

The emission of volatile chemicals has been referred to as the ability of plants to ‘talk’, that is, to emit information about their state of attack.

Rhoades, D.F. (1983) Responses of alder and willow to attack by tentcaterpillars and webworms: evidence for pheromonal sensitivity ofwillows. In In Plant Resistance to Insects In American ChemicalSociety Symposium Series 208, Washington, D.C., USA (Hedin, P.A.,ed.), pp. 55–68

Baldwin, I.T. and Schultz, J.C. (1983) Rapid changes in tree leafchemistry induced by damage: evidence for communication betweenplants. Science 221, 277–279

The effects of the Abiotic factors on plant herbivory interactions

Abiotic Factors:-LightTemperature, frost/low temperature Water- Water stress, water deficitNutrientsTopography – elevationRelative humidity Pollutionsalinity, wind

by Sandrine P. Gouinguené and Ted C.J. Turlings Institute of Zoology, Laboratory of Animal Ecology and Entomology, University of Neuchâtel, Case Postale 2, CH–

2007 Neuchâtel, Switzerland

Plant Physiol. 2002 July; 129(3): 1296–1307.

The Effects of Abiotic Factors on Induced

Volatile Emissions in Corn Plants

Sandrine et al finding

• Climatic conditions and nutrient availability can be important factors in determining the intensity and variability in the release of induced plant volatiles.

Sandrine et al.

• Spodoptera littoralis Egyptian Cotton

• Leafworm

The host plant was corn

Soil Humidity • Plants released more Volatiles when

standing in dry soil than in wet soil, whereas for air humidity, the optimal release was found at around 60% relative humidity

Sandrine et al.

Soil Humidity

Caterpillar (Spodoptera littoralis) regurgitant was either injected into the stem or applied to the scratched leaves of 10-d-old plants

?

Sandrine et al

Air Humidity

• whereas for air humidity, the optimal release was found at around 60% relative humidity

Sandrine et al.

Air Humidity

Total amount (ng/3 h) of induced volatiles emitted by corn plants under different air humidities. Circles represent the amount released by induced corn plants and squares represent the odor released by undamaged plants. Black curve represents the relation

Sandrine et al

Sandrine et al finding

• Temperatures between 22°C and 27°C led to a higher emission than lower or higher temperatures

• Light intensity had a dramatic effect. The emission of volatiles did not occur in the dark and increased steadily with an increase in the light intensity.

• Fertilization also had a strong positive effect; the emission of volatiles was minimal when plants were grown under low nutrition

Temperature

• Total amount (mean + se) of odor emitted by corn plants under different temperatures (°C). Black bars represent induced plants and white bars represent undamaged plants. Stars indicate significant differences between induced plants and undamaged plants (F = 35.148 and P < 0.001) and letters above black bars indicate significant differences among the different temperature tested for induced plants by Student-Newman-Keuls post hoc test (α = 0.05).

Sandrine et al

Light Intensity

• Light intensity had a dramatic effect (F = 19.174, P < 0.001, and df = 4), with an increase in release of volatiles as light intensity increased. Induced plants in the dark emitted very little odor and their releases were not different from the odor of undamaged plants. No significant effect of the light intensity was found for the releases by undamaged plants (F = 0.755, P = 0.577, and df = 4).

Sandrine et al

Light Intensity

• Total amount (mean + se) of volatiles emitted by corn plants under different light intensities. Black bars represent induced corn plants, and white bars represent undamaged plants. Stars indicate significant differences between the total amount

Sandrine et al

Light Cycle

Total amount (mean + se) of volatiles emitted by corn plants under dark-light phases. Black bars represent induced corn plants, and white bars represent undamaged plants. The horizontal bar represents the respective dark and light phases.

Sandrine et al

Fertilization Rate Sandrine et al

Fertilization Rate

Total amount (mean + se) of volatiles emitted by corn plants under three different fertilization rates (see text for details). The graph in A represents the amount without correction for biomass and the graph in B represents the amount corrected for biomass. END

Sandrine et al

Sandrine et al

• The magnitude and direction of this effect was different for each factor considered. Higher emission of induced volatiles occurred when the soil was relatively dry, the relative air humidity was between 45% and 65%, the temperature between 22°C and 27°C, with high light intensity, and with continuous fertilization of the soil. In many cases

Light• Diurnal emissions have also been reported for induced volatiles.

Loughrin et al. (1994) showed that the induced emission of volatiles in cotton (Gossypium hirsutum) plants (Malvaceae) was higher during the afternoon and significantly decreased at night.

• Similar results were reported by Takabayashi et al. (1994), who found that uninfested leaves of lima bean (Phaseolus lunatus; Fabaceae) placed under high light intensity are more attractive to predatory mites than when they are placed under low light conditions, which was due to different volatiles emission under the two light regimes.

• Maeda et al. (2000) reported the importance of light on the emission of induced volatiles in kidney beans (Phaseolus vulgaris) plants attacked by the spider mite (Tetranychus urticae). This corresponded nicely with the responsiveness of predatory mites; they were more active during light periods (Maeda et al., 2000).

Effects of Light on the Tritrophic Interaction Between Kidney Bean Plants, Two-Spotted Spider Mites and Predatory Mites, Amblyseius

Womersleyi (Acari: Phytoseiidae) byTaro Maeda et al.  • The volatiles from Tetranychus urticae-

infested kidney bean plants (Phaseolus vulgaris) at different times for two days, they found that they were mainly produced in the light. Tetranychus urticae showed a higher oviposition rate and spent more time feeding during the day (in the light)

Effects of Light on the Tritrophic Interaction Between Kidney Bean Plants, Two-Spotted Spider Mites and Predatory Mites, Amblyseius

Womersleyi (Acari: Phytoseiidae) byTaro Maeda et al. 

• Infested leaves placed in the light attracted the predatory mite Amblyseius womersleyi

• Amblyseius womersleyi dispersed more frequently and consumed more T. urticae eggs during the day (in the light)

water stress

• Takabayashi et al. (1994) reported that lima beans under water stress were more attractive to spider mites. With chemical analyses, they confirmed that lima bean plants under water stress produce more of the attractive volatiles than non-stressed plants. Their study was done with undamaged plants and they did not report on any effect of water stress on the emission of induced volatiles

Tetranychus urticae• An experiment conducted by Hollingsworth

and Berry (1982) revealed that densities of twospotted spider mites, Tetranychus urticae, increased more rapidly on peppermint plants that were under moisture stress than on nonstressed plants

Tetranychus urticae

• The greatest intensities of mites were observed on plants that had been fertilized with a high ratio of N to P and K. The researchers also reported that the largest populations of spider mites were associated with plants grown at higher air temperatures. This observation supports the earlier hypothesis of Simpson and Connell (1973) that high temperatures may be important for mite population expansion.

Tetranychus urticae

• moisture stress reduced both soybean plant and total spider mite population growth and apparently also reduced intensity." This pattern is similar to the trend observed with twospotted spider mites on radish plants (Mellors and Propts 1983),

J. A. G OOLSBY et al• CONTINENTAL COMPARISONS OF THE

INTERACTION BETWEEN CLIMATE AND THE HERBIVOROUS MITE, FLORACARUS PERREPAE (ACARI: ERIOPHYIDAE)

• J. A. G OOLSBY et alleaf roll galling mite, Floracarus perrepae (ACARI:

ERIOPHYIDAE)

The Old World climbing fern, Lygodium microphyllum

Florida

J. A. G OOLSBY et al

J. A. G OOLSBY et al

• Within sites the mean maximum temperature was the only significant weather variable, showing a decrease in the incidence of leaf rolls above 27°C, and it was predicted that no leaf rolls would form above 35°C.

J. A. G OOLSBY et al

• Mattson and Haack (1987) discuss several hypotheses that may explain why drought stress tends to promote outbreak of plant-eating arthropods. They listed the possible outcomes of a drought that could influence insect and plant interactions.

M. Gray et alAlthough mites are not insects, we assume that phytophagous

mites respond to drought conditions similarly to plant-eating insects, particularly those that have piercing and sucking mouthparts.

1. Drought provides a more favorable thermal environment for growth of phytophageous insects.

2. Drought-stressed plants are behaviorally more attractive or acceptable for insects.

3. Drought-stressed plants are physiologically more suitable for insects.

4. Drought enhances insect detoxification systems to some plant allelochemicals.

5. Drought may not favor natural enemies of phytophagous insects. 6. Drought may induce genetic changes in insects.

Plant Stress Hypothesis (PSH)• The plant stress hypothesis predicts that

environmental stresses on plants decrease plant resistance to insect herbivory by altering biochemical source–sink relationships and foliar chemistry, leading to more palatable food. Such changes in the nutritional landscape for insects may facilitate insect population outbreaks during periods of moderate stress on host plants.

• Source-sink dynamics is a theoretical model used by ecologists to describe how variation in habitat quality may affect the population growth or decline of organisms

Plant Stress Hypothesis (PSH)

• Traditionally, herbivorous insects are thought to exhibit enhanced performance and outbreak dynamics on water-stressed host plants due to induced changes in plant physiology. Recent experimental studies, however, provide mixed support for this historical view

Stress Hypotheses

• Three hypotheses predict how insect herbivores perform on stressed host plants.

• The plant stress hypothesis (PSH) predicts improved insect performance on stressed hosts.

• The plant vigour hypothesis (PVH) predicts that insects closely associated with their host, such as gall-formers, will perform better on vigorously growing non-stressed hosts.

• The Insect Performance Hypothesis (IPH) predicts that wood-feeders, sap-feeders and miners will perform better on stressed hosts, while leaf-feeders and gall-formers will perform better on non-stressed hosts.

• Archer et al. (1995) reported that the number of The Russian wheat aphid (RWA's) on wheat plants that are not irrigated was significantly higher than well watered wheat plants.

Water stress

Water stress alters the plant and its thermal environment so that plants become more susceptible and suitable for insect growth, survival and reproduction in many insect species, mainly because: (1) plant nutrients are either more concentrated or better balanced; (2) the plant becomes more favorable thermal environment; and (3) the plant has lower defenses (Mattson

and Haack, 1987b).

Pollution

The effects of environmental change on the insect-plant interaction are currently the subject of much investigation. Increasing atmospheric carbon dioxide concentration, and increasing availability of nitrogen due to depositing of nitrogenous pollutants and increased mineralization rates in warmer climate, both have a potential to alert plant nutritional quality and insect performance

EFFECTS OF HEAVY METAL POLLUTIONAND HOST PLANT LEAF CHEMISTRY

ON THE IMMUNE DEFENSE ANDLIFE HISTORY TRAITS OFAN INSECT HERBIVORE

byTapio van Ooik

Turku 2008

Pollution Tapio van Ooik

Mountain birch (Betula pubescens.czerepanovii) was the host tree

Autumnal moth, Epirrita autumnata family Geometridae

Phenoloxidase (PO) activity to gain moreinformation about immune defense in E.autumnata.

Pollution Tapio van OoikEven the pollution arising from the

factory complex at Harjavalta does not seem

to affect the moth very much. Pollution

decreases the growth of the larvae on Betula

pubescens leaves, but the moth seems to be able

to offset this by extending the time spent

consuming leaves before pupating.

Pollution Tapio van Ooik

The moderate amount of pollution at Harjavaltaenhances the moth’s immune defense, whichmay actually benefit the moth: enhancedimmune defense helps it to defend itselfagainst parasites and diseases Thus, whenpollution increases the immune response ininsects, the parasitism rates of insects maydecrease in metal-polluted areas. This couldlead to another outbreak of the moth

Pollution Tapio van Ooik

• It is noteworthy that he found sex differences in the immune function of the autumnal moth. Heavy metal pollution decreased PO activity in female moths, but in males the activity increased.

Pollution Tapio van Ooik

Additionally, we found clear differences between the sexes in their encapsulation rate. The encapsulation rate of females was higher in the heavy-metal treatment than in the controls, while male immunity showed no effect of treatment

Pollution Tapio van Ooik

This supports previous findings showing sex

differences in the effect of environmental and

genetic factors on immunity in E. autumnata

(Rantala and Roff, 2007). We suggest that this

is probably a result of sex differences in the

genetic architecture of the immune system

Pollution Tapio van Ooik

Pollution had also a large effect on thechemistry of mountain birch leaves. E.g.,heavy metals had among other things aneffect on the amount of phenoliccompounds. However, accumulation ofphenolics does not necessarily have anadverse effect on the performance ofherbivores

Air pollution increases Aphis fabae pest potential

G. P. Dohmen, S. McNeill & J. N. B. Bell

Nature 307, 52 - 53 (05 January 1984);

G. P. Dohmen

• We show here stimulatory effects of SO2 and NO2 and ambient London air on the growth of the black bean aphid, Aphis fabae, and demonstrate that these have been mediated entirely via the host plant.

Effect of air pollution at a motorway on the infestation of Viburnum opulus by Aphis fabae.

• The influence of air pollutants from cars on a motorway on the population development of the aphid Aphis fabae on potted Viburnum opulus was investigated in field experiments in Switzerland.

• After 3 weeks, artificially infested shrubs at the verge of the motorway were 5 times as infested with aphids as those 300 m away from the road.

• Chambers receiving ambient air had 8 times as many apterous aphids as those receiving filtered air after 4 weeks.

Bolsinger, M., Flückiger, W.

• Chamber experiments at the verge with filtered and unfiltered ambient air showed similar results,

Bolsinger, M., Flückiger, W.

• Many observations have been made of increased population densities of herbivorous insects in areas subject to air pollution