Vascular and Nonvascular Plants

Overview of Plants

• Over 300,000 different types of plants exist, each possesses unique adaptations suited for diverse environments
• Plants adaptations and structure are covered
• One misconception is that all plants need same light and water to thrive, diversity exists

Vascular vs. Nonvascular Plants

• The two main categories for classifying plants are vascular and nonvascular
• Xylem and phloem form the vascular system in plants and act as vessels or tubes
• Xylem transports water from roots, whereas phloem transports sugars from photosynthesis, to the entire plant
• Nonvascular plants do not have specialized transport tissues, meaning water and nutrients cannot be carried efficiently over long distances
• The absence of xylem limits the size of nonvascular plants, which rely on osmosis to obtain water, similar to a sponge
• Nonvascular plants are also referred to as bryophytes.
• Liverworts, hornworts, and mosses are types of bryophytes
• Nonvascular plants are typically small and are often found in damp environments, lacking true stems, leaves, and roots, but may have similar structures
• Vascular plants possess xylem and phloem with true stems, leaves, and roots.

Types of Vascular Plants

• Seedless vascular plants, gymnosperms, and angiosperms are the different kinds of vascular plants
• Seedless vascular plants don't produce seeds
• Lycophytes (e.g., clubmosses) and ferns are examples of seedless vascular plants
• Gymnosperms are "naked seeds" plants, not enclosed in fruits, like pine trees and other conifers
• Ginkgo, cycads, gnetophytes and conifers are types of gymnosperms
• Angiosperms (flowering plants), produce flowers and fruits, with seeds enclosed inside the fruit
• Angiosperms account for ~90% of all plant species
• Angiosperms are classified into monocots and dicots, which differ in several characteristics

Plant Structure and Photosynthesis

• The conversion of sunlight into sugar (primary food source) in plants is called photosynthesis
• Plant structure facilitates photosynthesis
• Photosynthesis requires water, carbon dioxide, and light
• Plants obtain water differently, depending on whether they are vascular or nonvascular
• Carbon dioxide is absorbed through stomata (small openings) usually located on the underside of leaves
• Stomata facilitate gas exchange allowing carbon dioxide to enter for photosynthesis and oxygen to exit as a byproduct
• Guard cells regulate opening and closing of stomata, responding to environmental conditions to balance gas exchange and water loss
• Stomata close at night to conserve water, if photosynthesis cannot occur without light
• Plant cells contain chloroplasts (organelles where photosynthesis takes place)
• Pigments like chlorophyll capture light energy inside chloroplasts
• Chlorophyll absorbs specific light wavelengths (red and blue) to fuel the photosynthetic process
• Leaf structure varies with the plant's environment
• Plants in dry areas may have small, thin leaves or waxy coatings to minimize water loss
• Plants in shaded, moist environments may have broad leaves to maximize sunlight capture

Unique Plant Adaptations

• Carnivorous plants (Venus flytraps and pitcher plants), supplement their nutrient intake by trapping/digesting insects
• Carnivorous plants typically grow in soil with low nitrogen, so they obtain it from insects through specialized enzymes
• Mangrove trees (in waterlogged soils), possess roots to cope with low oxygen and high salt concentrations
• Parasitic plants (mistletoe), steal nutrients and water from host plants through haustoria (specialized structures)

Importance of Plants

• Plants form the food web foundation and are essential for life
• Plants provide ingredients for many medicines
• Plant photosynthesis produces oxygen for human and animal respiration