Plants BFI

• White light is a mixture of 7 different colors
• Photosynthesis converts solar energy into chemical energy
• Almost all plants are photoautotrophs, using sunlight energy to make organic molecules
• Photosynthesis occurs in plants, algae, certain unicellular eukaryotes (protists), and some prokaryotes
• Leaves reflect green light and absorb other colors to empower photosynthesis
• Chlorophyll a is the main photosynthetic pigment, while accessory pigments like chlorophyll b broaden the spectrum used for photosynthesis
• Carotenoids absorb excessive light that can damage chlorophyll
• Diffusion is the passive movement of molecules from high to low concentration, while active transport requires energy to move molecules against their concentration gradient
• The Calvin cycle inputs are CO2, ATP, and NADPH, with outputs of glucose (3C molecule) and ADP
• The light-dependent reactions occur in the thylakoid membranes of chloroplasts, while the light-independent reactions (Calvin cycle) take place in the stroma of chloroplasts
• Steps in the Calvin cycle:

  • Sunlight causes chlorophyll electron flow into thylakoids membrane
  • Water is split into H+, e-, and O components
  • The electron transport chain generates NADPH and ATP energy
  • CO2 combines with RuBP
  • ATP breaks down a 3C molecule into a 5C molecule
• Major developments in the evolution of plants:

  • Origin from green algae about 470 million years ago
  • Early plants developed reproductive structures, photosynthetic branches, and structures anchoring the plant to the soil
  • Gave rise to nonvascular plants (mosses), seedless vascular plants (ferns), and seed plants (cone-bearing and flowering plants)
• Alternation of generations in plants involves distinct multicellular organisms: gametophytes and sporophytes
• Alternation of generations includes:

  1. Haploid gametophyte producing haploid gametes by mitosis

  2. Fusion of gametes forming a diploid sporophyte

  3. Sporophyte producing haploid spores by meiosis

  4. Spores developing into multicellular haploid gametophytes
• Multicellular, dependent embryos in plants develop from zygotes retained within the tissues of the female parent
• Sporophytes and sporangia of mosses:

  • Each spore produced by a sporangium is encased by a durable, sporopollenin-enriched wall
• Archegonia and antheridia of liverworts:

  • Archegonia are female gametangia containing eggs
  • Antheridia are male gametangia containing sperm
• Apical meristems are the growing tips of plant roots and shoots
• Land plants diversified with adaptations to thrive despite challenges like scarcity of water, lack of structural support against gravity, and less appropriate environment for pollination
• Land plants vs charophytes:

  • Charophytes lack five key traits present in land plants, including alternation of generations and multicellular, dependent embryos
  • Both land plants and charophytes are multicellular, photosynthetic, eukaryotic, have cell walls, and chloroplasts
• Vascular plants have well-developed roots and leaves, xylem and phloem tissues, and dominant sporophytes in their life cycles
• Life cycle of a moss:

  • Spores develop into protonemata
  • Protonemata produce buds that grow into gametophores
  • Male gametophyte has antheridia producing sperm, female gametophyte has archegonia producing eggs
  • Fertilization occurs within the archegonium, forming a zygote that develops into a sporophyte embryo
• The prickly pear cactus is a succulent plant native to North and South America, with a segmented stem covered in spines and glochids, producing yellow or red flowers and sweet cactus pears as fruit
• A diagram of a flowering plant shows roots (absorb water and nutrients), stem (supports leaves and flowers), leaves (produce food through photosynthesis), and flowers (produce seeds)
• Roots perform functions like anchoring the plant, absorbing minerals and water, and storing carbohydrates
• Types of roots include prop roots, storage roots, green roots, pneumatophores, and strangling aerial roots
• Stems consist of nodes, internodes, axillary buds, and apical buds, with adaptations like stolons, rhizomes, and tubers
• Leaves are the photosynthetic organs of a plant, with adaptations like spines, tendrils, and storage capabilities
• Monocots and eudicots can be differentiated based on leaf venation: monocots have parallel veins, while eudicots have branching veins
• Ground tissues in plants include sclerenchyma, collenchyma, and parenchyma cells, each with specific characteristics like lignin content and metabolic functions
• The xylem is a tissue in plants that transports water and minerals from the roots to the leaves, made up of vessels, tracheids, and fibers
• Vessels in the xylem are the largest cells and transport water and minerals quickly
• Tracheids in the xylem are smaller than vessels and also transport water and minerals
• Fibers in the xylem are the smallest cells and provide support
• Xylem and phloem are vascular tissues that transport water and minerals in one direction and sucrose and organics in two directions, respectively
• Water transportation through xylem involves evaporation from leaves, capillary action forming a water column, and passive transport into roots and xylem by osmosis
• Phloem transports food materials, including sugars, amino acids, micronutrients, lipids, hormones, and proteins, from leaves to other parts of the plant
• Phloem fibers store and provide strength, transporting sugars from leaves to the rest of the plant
• Translocation in the phloem involves sugar loading, water flow by osmosis, downward sap movement, unloading sucrose into the sink, and water moving back into xylem by osmosis
• Xylem moves water and minerals upwards from roots to leaves, while phloem moves sugars and nutrients from leaves to the rest of the plant