ICAR JRF Plant Form and Physiology — practice questions — page 4

1. Jasmonate levels rise when a plant is wounded by a predator. 2. They promote the synthesis of compounds that are toxic to predators. 3. They also elicit volatile compounds that attract parasitoids. 4. Parasitoids are insects that spend their developing stages in or on another insect and eventually kill their host. 5. So the plant recruits an enemy of its enemy rather than a pollinator. 6. Nitrogen fixing bacteria and root colonising fungi are nutritional partners recruited under quite different signals. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 30 "Plant Form and Physiology", section 30.6 Plant Sensory Systems and Responses_

1. Thigmomorphogenesis is a slow developmental change in the shape of a plant under continuous mechanical stress. 2. When trees bend in the wind, growth is usually stunted and the trunk thickens. 3. Strengthening tissue, especially xylem, is produced to add stiffness against the force of the wind. 4. A narrower trunk would be less able to resist bending, so it is the opposite of the observed response. 5. Ethylene and jasmonate are likely to be involved in this response. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 30 "Plant Form and Physiology", section 30.6 Plant Sensory Systems and Responses_

1. Secondary metabolites are compounds not directly derived from photosynthesis and not needed for respiration or growth. 2. Many are toxic and some become toxic only after ingestion. 3. Glycol cyanide in the cassava root releases cyanide only when a herbivore eats it. 4. Quinine works instead through a repellent bitter taste and needs no conversion. 5. Caffeine acts by excessive stimulation of the herbivore, again without waiting for ingestion to activate it. 6. Volatile oils such as those of mint and sage discourage predators by odour before any feeding occurs. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 30 "Plant Form and Physiology", section 30.6 Plant Sensory Systems and Responses_