bio chapter 40 notes

Bio chapter 40 - Plant Defense Responses Life on Land is not all Milk and Honey Chapter 40 Click to edit Master subtitle style Physical Defenses

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Click to edit Master subtitle style Plant Defense Responses – Life on Land is not all Milk and Honey Chapter 40
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Physical Defenses Winds can uproot a tree, or snap the main shoot of a small plant Axillary buds give plants a second chance as they grow out and replace the lost shoot 22 Fig. 40.1 – Shoots in reserve
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Even greater daily threats exist in the form of viruses, bacteria, fungi, animals, and other plants These can tap into nutrient resources of plants or use their DNA-replicating mechanisms to self-replicate Some kill plant cells immediately, leading to necrosis 33 Some things axillary buds cannot protect against
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One of the greatest problems with nonnative invasive species , such as the alfalfa plant bug, is the lack of natural predators in the new environment 44 Alfalfa plant bug Fig. 40.2 – The Alfalfa Plant Bug.
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Dermal tissue system First-line defense of all plants Epidermal cells throughout the plant secrete wax to protect plant surfaces from water loss and attack Above-ground parts also covered with cutin Suberin is found in cell walls of subterranean plant organs Silica inclusions, trichomes , bark, and even thorns can also offer protection 55 So, what is a plant to do?
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These exterior defenses can be penetrated Mechanical wounds allow microbial entry Parasitic nematodes use their sharp mouth parts to get through the plant cell walls Some form tumors on roots In some cases simply having bacteria on the leaf surface can increase the risk of frost damage 66
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77 Fig. 40.3 – There are “good” nematodes – and “not-so-good” nematodes – these attack the roots of plants.
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Fungi seek out the weak spot in the dermal system, or stomata, to enter the plant Phases of fungal invasion 1. Windblown spore lands on leaves 2. Spore germinates and forms adhesion pad 3. Hyphae grow through cell walls and press against cell membrane 4. Hyphae differentiate into haustoria 88 And, the problem is more than just animals!
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99 Fig. 40.5 – Fungi can enter through the stomata.
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Fungi and bacteria can also be beneficial to plants Mycorrhizal fungi Nitrogen-fixing bacteria like Rhizobium Plant growth-promoting rhizobia (PGPR) Bacteria provide substances that support plant growth Can also limit the growth of pathogenic soil bacteria 1010 The Presence of microbes cuts both ways -
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Toxin Defenses – Plant Secondary Compounds/Metabolites Many plants produce toxins that kill herbivores, make them ill, or repel them with strong flavors or odors Some are unique to plants Defensins are found in plants AND animals Small, cysteine-rich peptides with antimicrobial
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This note was uploaded on 06/06/2011 for the course BIOL 1105 at Virginia Tech.

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Bio chapter 40 - Plant Defense Responses Life on Land is not all Milk and Honey Chapter 40 Click to edit Master subtitle style Physical Defenses

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