PLB143 MT2 Guide Revised

PLB143 MT2 Guide Revised - PLB143: STUDY QUESTIONS FOR...

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Unformatted text preview: PLB143: STUDY QUESTIONS FOR MIDTERM 02 Lecture 8: What is a Crop? Definitions: Vicarious domestication • If one species proves suitable for domestication, then a similar related species is likely to be useful as well • Repeated domestication in several locations across the world o Cotton has distributions across the world and in several locations you see repeated domestication • Same kinds of plants were selected in different parts of the world at the same time • Ex: If Mexican Indians domesticated a species, South American Indians domesticated similar species and vice versa • Ex: Old World vs. New World: Cotton was domesticated in Africa, India, America Also Lupin is also an example Polyploidy • Organisms containing more than two paired set of chromosomes • It may have contributed to preferential survival of lineages • Contributes to new gene functions, epigenetic changes, altered gene expression, CO2 exchange rate, hormone levels, photosynthetic rates, water balance, increased size (gigantism), and broader adaption o Hypothesis of Fawcett et al: polyploidy increased chances of survival during a major upheaval o Alternative hypothesis: polyploidy promotes speciation • New traits appear during or after polypliodization o Could promote domestication • Ex: Bread wheat: AABBDD o Leavened bread gluten is elastic protein matrix trapping gases produced by yeast Domestication syndrome • Fully domesticated plants are characterized by a similar set of traits that confer adaption to the human environment • The two most important traits of the syndrome in seed-propagated plants are loss of seed dispersal and loss of seed dormancy • The specific details for each trait will depend for each crop: gene, tissue or organ, etc. • Humans select for loss of seed shattering, bigger seed size, increase in seedling vigor, increase in inflorescence size and decrease in number of inflorescence. o Fully domesticated plants have most of the traits of the syndrome but generally not all of them o Within a crop, differences in the degree of domestication can be observed • Harlan, de Wet, and Price recognized a whole syndrome of trail associated with inadvertent selection due to planting and harvesting of cereal that others have called domestication syndromes o They felt harvesting resulted in the selection of the non-shattering trait, more determinate growth, and an increased seed production o The seedling competition caused by planting increased seeding vigor and rate of germination o This was associated with greater seed size and loss of germination inhibitors • Ex: When corn originated it had several small two-ranked fragile ears, while modern corn has 1 large many ranked non-fragile ear surrounded by husks(reduction in number of inflorescence and increase in inflorescence size) Questions: 1. Discuss what defines a crop that is cultivated compared to a crop that is domesticated....
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This note was uploaded on 10/17/2011 for the course PLB 143 taught by Professor Gepts during the Spring '07 term at UC Davis.

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PLB143 MT2 Guide Revised - PLB143: STUDY QUESTIONS FOR...

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