(DLP) Diversity of Life : Plants Module Overview

Plants

"Of the more than 250 thousand known plant species, less than 1 percent have been thoroughly tested for medical applications. Yet out of this tiny portion have come 25 percent of our prescription medicines."

Medicines are just one of the many reasons why plants are important.

Can you think of any other plants that have impacted society? Try to imagine a world without cotton or peanuts. Hard to imagine, right?

In order to understand the potential uses of plants, we must first learn about the structure and function of plants, as well as the classification of plants.

Module Lessons Preview

In this module, we will study the following topics:

• Plant Structure and Function
  • Learn the anatomy and physiology of plants
• Plant Adaptations
  • Learn about the unique adaptations plants have to survive in various environments.
• Plant Classification and Evolution:
  • Learn the taxonomy of plants and how they have evolved over time.
• Plant Reproduction
  • Learn about how plants reproduce.

Module Key Terms

• Botany- the study of plants
• Dermal tissue- outer layer of cells on plant parts; they protect the plant and prevent water loss
• Vascular tissue- tissues that conduct water, solutes, and nutrients throughout the plant; examples are xylem and phloem
• Ground tissue - all tissues besides dermal and vascular tissues
• Xylem- tissue that transports water from roots to shoots in plants
• Phloem- tissue that transports nutrients in a plant; usually downward
• Meristem- growth regions in a plant where cells are actively dividing by mitosis
• Primary growth- the type of growth where stems increase in length and occurs in apical meristems at shoots and roots
• Secondary growth- the type of growth where stems increase in width and occurs in lateral meristems
• Vascular cambium- layer of actively dividing cells between xylem and phloem in a plant stem that make new wood (xylem) to inside of stem and new bark (phloem) outside of stem
• Apical meristem- located at the tips of roots and stems; this actively dividing region of cells produces growth in length known as primary growth
• Cork cambium- located outside the phloem; it produces the bark, or cork
• Bark- outer protective layer and waterproof layer of stem
• Cortex- storage cells between cambium and epidermis ; layer of ground tissue of root that serves to store carbohydrates from photosynthesis
• Pith- original stem at the very center of stem
• Heartwood- inner, older rings of a woody stem; has undergone a genetically programmed change that results in cell death, but protection from decay
• Sapwood- outer, inner rings of a woody stem
• Taproot system- a thick vertical root with many smaller side roots; they serve as reserves for food and help to anchor the plant
• Fibrous root system- small lateral roots that extend just below the soil surface; help in increase water absorption, anchor the plant, and prevent soil erosion
• Root hairs- small extensions of a root; increase surface area of a root for water absorption
• Root cap- a shield of parenchyma cells covering the apical meristem at the root tip
• Endodermis- protective inner layer of root that completely encloses the inner vascular tissue
• Vascular cylinder - inner central cylinder of root composed of xylem and phloem
• Node- areas where side branches and leaves develop on a plant stem
• Internode- regions between nodes on a plant
• Nonvascular- a plant that has no specialized system to transport water, nutrients, or food (lacks phloem and xylem)
• Tropsim(tropos – “turn”) – is a directional response to a stimulus; examples include phototropism, gravitropism, and thigmotropism
• Auxin- plant chemical messenger (hormone) that allows plant tropism by causing more or less growth in plant stems
• Nastic movements- response to stimuli (light, temperature, touch) that are nondirectional
• Circadian responses- “sleep movements”; plant movements in response to time of day
• Xerophyte- a plant that is adapted to dry environments
• Hydrophyte- a plant that is adapted to very wet environments
• Epiphytes- do not live off the soil or ground; instead they grow on branches of trees
• Cutin/cuticle- a wax that covers plants surfaces; protecting the plant from water loss or drying out
• Lignin- a complex polymer in plants that helps to strengthen cell walls and allows plants to grow taller and support heavier/larger surfaces
• Alternation of Generations- a type of life cycle common in plants where a gametophyte body form alternates with a sporophyte body form
• Haploid- one set of chromosomes for a species (N)
• Diploid- two sets of chromosomes for a species (2N)
• Gamete- sperm or egg produced by the gametophyte of the plant
• Spore- product of meiosis produced by the sporophyte generation of the plant
• Zygote- a fertilized egg
• Gametophyte- haploid, multicellular stage in the life cycle of plants; it originates from a spore and its function is to produce gametes
• Sporophyte- diploid, multicellular stage of the life cycle of plants; it originates from a zygote and its role is to produce spores by meiosis
• Bryophytes- non-vascular plants that have no specialized system to transport water, nutrients, or food (ex. mosses)
• Pteridophytes - vascular plants without seeds (ex. ferns)
• Gymnosperms- (naked seed plant); vascular seed plants that do not have flowers or fruit, but may have cones as their reproductive structures
• Angiosperms- (flowering plants); vascular seed plants with flowers and the seed is enclosed in the ovary that develops into the fruit
• Monocots- angiosperms with parallel leaf veins, petals in groups of three, and one seed cotyledon
• Dicots- angiosperms with branched leaf veins, petals in groups of fours and fives, and two seed cotyledon
• Tracheophyte- any plant with vascular tissue
• Spermatophyte- generic term for all seed plants and includes the gymnosperms and angiosperms
• Capsule- portion of moss sporophyte where meiosis occurs to make spores
• Seta- stalk that supports moss capsule on the green portion of the plant
• Archegonium- part of the gametophyte that produces eggs
• Antheridium- part of the gametophyte that produces sperm
• Frond- leaflets on both sides of the stem from the mature fern
• Fiddlehead- young fern fronds that have not unfurled
• Sporangia- “spore vessel” plant reproductive structure in which spores are formed/housed until released
• Sori- cluster of sporangia found underneath fern leaflets
• Peat- a mass of decayed plants and/or organic matter that overtime may form coal and serve as a carbon sink for the ecosystem
• Pollen- the spore of seed plants that produce/contains sperm
• Female Cone or Ovulate cone- larger woody cones and they produce eggs
• Male cone or Pollen cone- smaller, slender cones and they produce pollen
• Flower- reproductive structure found in angiosperms. Evolutionarily, it is a collection of highly modified leaves bearing reproductive organs
• Stamen- male reproductive structure in flowers that is composed of a thin stalk (filament) and an enlarged structure (anther) that produce pollen
• Anther- male reproductive part that produces and releases pollen
• Filament- supports the anther and is part of the stamen
• Carpel- one or more carpals make up the pistil; Evolutionarily, it is a highly modified leaf
• Pistil- female reproductive structure in plants composed of a stigma, style, and ovary; the eggs are produced at the bottom of the pistil
• Stigma- sticky top of the pistil that receives the pollen
• Style- slender, tube portion of the pistil connecting stigma to ovary
• Ovary- bottom of pistil where eggs are produced and where fertilization occurs; the ovary develops into fruit when mature
• Petal- whorl of leaves in a flower between the stamen and sepals; most serve to attract pollinators
• Sepal- outermost whorl of leaves in a flower and protective covering of buds
• Complete flowers- flowers with all 4 whorls of parts – sepal, petal, stamen, carpal – ex. roses