Assignment 1 - Teff (*Eragrostis tef*)

Botanical Information

• Belongs to the Poaceae (grass) family.
• Type:
  • Herbaceous plant.
  • Considered an annual.
• Native distribution primarily in the Horn of Africa, particularly Ethiopia and Eritrea.

History as a Food Plant

• First domesticated in Ethiopia around 4000-1000 BCE.
• Most widely grown in Ethiopia, where it is a staple food crop.

Utilization

• The edible part of the plant is the seed.
• Seeds are ground into flour, which is commonly used to make traditional dishes like injera, a fermented flatbread.
• Harvested by cutting the plants at maturity, followed by threshing to separate seeds from chaff.
• Seeds can also be processed into porridge or brewed as a beverage.

History of Plant Classification

• Plant classification has roots in Ancient Greek times, aimed at developing a natural grouping system.
• Key classification questions include the criteria for grouping organisms and the definition of similarity.
• Early classification systems were artificial, focused on plant appearance and medicinal properties, not evolutionary relationships.
• Theophrastus, a student of Aristotle, established the first plant classification system around 2300 years ago, recognizing families like Pea and Sunflower.
• The Age of Herbals (1470-1670) expanded plant knowledge through herbal manuscripts that illustrated plants and their medicinal uses, creating issues with inconsistent common names.
• A standardized Latin-based nomenclature emerged to resolve confusion around common names.
• Carl Linnaeus simplified plant naming with the binomial system, introduced in Species Plantarum (1753), comprising a generic name and species epithet (e.g., Picea glauca).
• The binomial nomenclature is governed by the International Code of Botanical Nomenclature, including rules on capitalization, italicization, and authority designations.

Plant Species

• Classification is centered on the species concept, defining a biological species as a group able to interbreed but not with others, producing sterile offspring.
• Applying this definition presents challenges in plants due to spatial separation, hybrid fertility, and asexual reproduction in certain species, like the dandelion (agamospermy).
• Morphological classification (studying form, structure, and size) is commonly employed, though environmental factors influence plant morphology and may complicate classification.
• Morphological plasticity means that plants' forms can change drastically based on environmental conditions; for example, potentilla is light-sensitive.

Evolutionary Relationships of Flowering Plants

• Morphologically-based classifications (phenetic systems) use conservative characters while avoiding highly variable traits.
• The publication of Charles Darwin's Origin of Species (1859) sparked interest in phylogenetic classification emphasizing evolutionary relationships.
• Classification depends on understanding ancestral relationships and defining primitive versus advanced plant features, complicated by poor fossil records.
• Two historical theories on flowering plant evolution proposed by Engler and Hooker differ in the complexity and characteristics of early flowers.
• The modern consensus aligns with Hooker’s modified view, recognizing 300 to 350 flowering plant families, corroborated by molecular biology advancements.

Flowering Plants: Monocots and Eudicots

• Angiosperms are traditionally divided into monocots (one cotyledon) and eudicots (two cotyledons).
• Monocots display herbaceous forms, floral parts in threes, linear leaves with parallel veins, and short-lived primary roots.
• Eudicots exhibit broad leaves with net veins, floral parts in fours or fives, and often have persistent primary roots forming a taproot.
• Recent genetic studies reveal the division into monocots and eudicots is simplistic; a third group, magnoliid Angiosperms, predates their divergence.
• Economically significant magnoliid families include:
  • Magnoliaceae: horticultural and timber species.
  • Lauraceae: spices like cinnamon and avocado.
  • Annonaceae: tropical fruits, including soursop and custard apple.
  • Piperaceae: black pepper.
  • Myristicaceae: nutmeg and timber species.

Domestication of Plants

• Occurred approximately 10,000 years ago, transitioning from hunter-gatherer societies to settled agricultural communities.
• Hunter-gatherers had limited population due to seasonal food supplies, necessitating a nomadic lifestyle.
• Early humans were omnivores and crucially relied on plants for food, medicine, and psychoactive substances.
• Modern-day hunter-gatherer societies, like the !Kung of central Africa, spend two days per week acquiring food, allowing for leisure time.

Shift to Agriculture

• Settling in one place offered advantages: reliable food supply, access to trade routes, and consistent water sources.
• This shift led to cultivation of plants, domestication of animals, and permanent settlements.
• Resulted in increased food reliability, larger populations, greater environmental control, and specialization in roles.

Origins of Agriculture

• Defined as tilling land for the deliberate planting of crops; provides year-round food supply.
• Independent development of agriculture occurred in Asia Minor, China-Southeast Asia, and the Americas between 5,000-7,000 years ago.
• Earliest agricultural indications found in arid regions such as the Fertile Crescent (modern Iraq, Iran, and Turkey).

Theories of Domestication Transition

• Childe's Theory: Humans and herd animals congregated near watering holes, which led to soil disturbance and favoring of "weedy" grass species, initiating the Neolithic Revolution.
• Sauer's Hypothesis: Sedentary living emerged in favorable climates, with less optimal areas being settled as populations grew, compelling plant domestication.
• Anderson's Theory: Highlights the role of weeds in creating genetic variation in disturbed habitats, leading to domesticated plants.
• Binford and Flannery's Hypothesis: Early gatherers became skilled botanists, leading to gradual cultivation necessity driven by population pressures.

Centers of Agricultural Origin

• Asia Minor (Near East): Evidence from Jarmo indicates the cultivation of wheat and barley, along with domestication of goats, sheep, and various crops; urban civilization developed in Tigris-Euphrates valleys around 6,000 years ago.
• Central China (Far East): Agriculture evidence from the Yang-Chao site shows developed rice agriculture and complex societies dating back roughly 6,000 years.
• Central America: Agriculture emerged slower in Central America compared to Asia Minor, with key developments like the domestication of maize and other crops appearing around 7,500 years ago.

Agricultural Developments in Central America

• Transition from hunter-gatherer lifestyles to agricultural practices was gradual, with a mix of cultivation and wild harvesting.
• By 3,500 years ago, significant agricultural practices included the domestication of various crops like corn, tomatoes, and squash.
• Advanced agricultural practices by 2,500 years ago showcased irrigation systems and selective crop cultivation by Aztec, Mayan, and Inca civilizations.

Selection Pressures on Plants

• Plant characteristics evolve through the cumulative effects of the genome and natural selection.
• Cultivation of wild plants leads to significant modification of their phenotypic traits.
• Passive selection occurs when the link between planting and harvesting promotes beneficial cultivars, even without deliberate selection.
• Wild plants produce many seeds that mature over time, leading to some seeds surviving unfavorable conditions.
• Genotype 1: Seeds mature slowly, few at once; Genotype 2: Seeds mature simultaneously, resulting in higher harvest efficiency.
• Characteristics favored in cereal crops include:
  • Uniform seed maturation for consistent harvest.
  • Compression of tillering to encourage synchronous seed maturity.
  • Loss of seed appendages to prevent shattering before harvest.
  • Simultaneous germination by removing chemical inhibitors.
  • Increase in number of florets for more seed production.
  • Reduction of day-length sensitivity for adaptability to varied climates.
  • Loss of shattering to retain seeds on the plant until harvest.
  • Increased starch reserves in seeds to enhance seedling competition and growth.
• Weedy species adapt by synchronizing seed maturity with crop plants, complicating harvesting.

Geographic Origin and Spread of Plants

• Many common food plants had restricted original distributions; introductions transformed agriculture and diets.
• Notable introductions include:
  • Potatoes from South America to Europe.
  • Tomatoes and chili peppers from South America to other regions.
• Romans brought Mediterranean species to Northern Europe, while Arabic colonization introduced rice and citrus.
• European colonization significantly reshaped crop distributions, such as corn and potatoes spreading across Europe.
• Asia boasts many indigenous crops, particularly rice; significant American introductions include corn and chili pepper.
• Africa's indigenous food plants include coffee and millet, with important introductions from Asia and the Americas.
• The Americas are rich in native crops such as maize and potatoes, with few crops originating in North America.

The Green Revolution

• Focus on high-yield crops has led to trade-offs in disease and pest resistance.
• These crops generally require intensive resources: fertilizers, water, and pesticides.
• The Green Revolution often benefits wealthy nations and large-scale farms while disadvantaging developing regions.
• Monocultures increase vulnerability to pests and diseases, exemplified by the Irish potato famine due to reliance on a single crop variety.
• The cycle of breeding for yield often results in pests adapting and necessitating new resistant cultivars.

Plant Breeding: Genetic Modification

• Plant breeding methods include genetic crossing, back-crossing, artificial doubling of chromosome numbers, and genetic mutation.
• Genetic crossing maintains hybrid vigor in crops, with cloning methods like grafting and tissue culture facilitating propagation.
• Triticale, a hybrid of wheat and rye, offers higher resilience and yields, developed in the 1960s.
• Colchicine is used to induce polyploidy in plants, resulting in increased size and robustness—prevalent in many modern crops.
• Genetic mutations can promote beneficial traits; Brussels sprouts are a notable example of a successful spontaneous mutation.
• Genetic engineering introduces genetic information from other organisms to enhance crop traits; common crops include genetically engineered canola and corn.
• Strong consumer resistance to GE crops in Europe has led to regulatory challenges, and concerns persist about ecological impacts and accessibility for farmers in developing nations.

Genetic Diversity

• A diverse genetic pool is crucial for developing new crop varieties and medications.
• Loss of older plant varieties limits available genetic resources beneficial for breeding programs.
• Geneticists are seeking old cultivars, such as apples, to inform new variety development.
• Tropical rainforests house a significant portion of Earth's species and genetic resources, with many plants yet to be discovered that could offer essential food or medicinal benefits.

This quiz explores the botanical classification, history, and utilization of Teff, a vital food plant. Participants will answer questions regarding its family, types, native distribution, and processing methods. Dive deep into the significance of this important crop and its role in agriculture.