Review Notes for Exam - Responses of Plants to Herbivores | BSCI 494, Study notes of Biology

Download Review Notes for Exam - Responses of Plants to Herbivores | BSCI 494 and more Study notes Biology in PDF only on Docsity! RESPONSES OF PLANTS TO HERBIVORES 1. Modes by which plants cope with herbivory 2. Tolerance and resistance to herbivory 3. Miscellaneous ways of mitigating the effects of herbivory. There Are Various Mechanisms By Which Plants Cope With Herbivory BEING EPHEMERAL AND/OR AN UNPREDICTABLE RESOURCE. Not only plants but tissues or organs of plants can escape herbivory by being ephemeral and/or an unpredictable resource. However, Ultimately a Plant Has a Variety of Ways in Which it Can Cope with Herbivory and it May Utilize One or More Mechanisms in Addition to Escape and Evasion. For example Seeds May Escape Specialist Seed Predators in a Variety of Ways Seeds can escape by . Being too small to handle by predators or . Being too small to provide sufficient food value to merit search and handling effort. . Germinating too quickly to allow the feeding herbivore to develop within the seed. . Containing toxins . Occurring in such large numbers that predators are satiated (masting) . Being dispersed so efficiently that seeds are removed as soon TOLERANCE 2 Tolerance to Herbivory of Plants Is Defined as the Lack of Measurable Impact on a Plant of Any Given Degree of Damage by an Herbivore, Without the Initiation of Any Compensatory Process by the Plant. Implicit in this phenomenon is that the components and/or processes essential for growth, maintenance and reproduction exist in excess of basic requirements. Tolerance may be a whole plant response or only certain tissues of a plant may be tolerant of herbivory. Tolerance may be achieved at a population level in which the losses of a few individuals have no significant impact on ultimate primary productivity, i.e., it is the same as it would have been if herbivores had been absent or had not eliminated the individual plants. GROWTH RATE COMPENSATION When a plant is subject to herbivory, if the rate of plant weight loss (i.e., area loss per unit time; e.g., 30 g per week) is less than the rate of loss due to animal feeding (e.g., 40 g per week), the plant is said to compensate for herbivory feeding. . Ifa plant that is being eaten by an herbivore gains 50 grams a day and the herbivore eats 40 grams of plant tissues the plant is compensating. When the rate of weight loss by the plant equals or exceeds the loss rate due to animal feeding the plant is not compensating and herbivory is damaging (interfering with normal growth and maintenance). PLANT COMPENSATION CAN OCCUR THROUGH FIVE MAIN PROCESSES ° Reduced competition with other plants. . Increased unit leaf rate (net photosynthesis per unit leaf area) . Mobilization of stored carbohydrates or protein reserves to form regrowth tissues. ° Alteration of patterns of photosynthate distribution . Alteration of the normal rate of mortality of plant parts. However, the ability of plants to compensate for herbivory is affected by Evolved Adaptations to Reduce And/or Avoid the Probability of Encounter Between Plant and Herbivore; or to Reduce And/or Avoid Damage to Plants From To Susceptibility === Tolerance ———= Resistance Through Evolved Traits And/or Responses _ Such As Escape in Time Life-history Changes Morphological Defenses Physiological/Behavioral Compensation/Defense Chemical / Physical Defenses TAGLE Multiple Functions of Similar Traits: a Reflection of Adaptation and Preference. Factors Inhibitory to Herbivores # Sequestered or Secreted Toxins 4 Physical Traits Plant Traits Beneficial to Herbivores ¢ Host - Finding Sequestered or Secreted Cues ¢ Nutrients 4 Physical Traits