The Plant Kingdom

Characteristics of Plants

What makes a plant a plant? How are organisms in the plant kingdom different from organisms in other kingdoms?

• Plants are eukaryotic, unlike bacteria in the Eubacteria and Archaebacteria Kingdoms. This means plants have a nucleus and some organelles within their cells.
• Plants use photosynthesis to gain energy, unlike organisms in the fungi and animalia kingdoms. (There are a few parasitic plants that do not use photosynthesis.)
• Plants are multicellular unlike bacteria, some fungi, and some protists.
• Plants reproduce sexually.
• Plants have an alternation of generations life cycle, which means plants that make gametes alternate with plants that make spores.
• The cells of plants have cell walls unlike the cells of animals.
• Plant cell walls contain cellulose unlike the cell walls of organisms in the Fungi and Eubacteria kingdoms.
• Plants have a waxy coating, called the cuticle, on the surface of the stems and leaves. This helps prevent the plant from drying out.

What adapations do plants have which allow them to live on land?

• A waxy coating, called the cuticle, on the leaves and stems to keep the plant from drying out.
• A way to reproduce on land, since the gametes didn't have water to swim in: pollination.
• A way to absorb water and nutrients from the soil: roots.
• A way to move oxygen and carbon dioxide into or out of the plant: stomata (tiny holes in the bottom of the leaves).
• A transportation system for carrying water and carbohydrates throughout the plant: vascular system.
• A support system for the plant: fibrous/woody structures and vascular tissues.

Nonvascular Plants

Nonvascular plants do not have true roots, stems, or leaves.

• Nonvascular plants do not have a vascular system to transport water and nutrients throughout the plant. Instead, they use osmosis and diffusion to transport water and nutrients within themselves.
• Because they must rely on osmosis and diffusion, nonvascular plants are small.
• Nonvascular plants require water for reproduction. Unlike vascular plants, the sperm must swim to the eggs of another plant of that same species.
• The gametophytes in nonvascular plants are larger than the sporophytes. When you look at moss, what you are mostly seeing is the gametophyte. The gametophytes are the part of the plant in which gametes are formed. Sporophytes are the part of the plant that produces spores. Remember that in an alternation of generations, gametophytes alternate with sporophytes.
• Rhizoids, which are hairlike projections, hold the gametophyte to the rock, base of a tree trunk, or other surface on which it grows.
• The sporophytes grow on the gametophytes.

Seedless Vascular Plants

• Seedless vascular plants are larger than nonvascular plants.
• They have true roots, stems, and leaves.
• They have xylem and phloem which carry water, nutrients, and sugars around the plant.
• Seedless vascular plants have sporophytes that are larger than their gametophytes. In fact, the gametophytes are usually below the surface of the soil.
• Seedless vascular plants require water during fertilization to enable the sperm gametes to swim to the egg gametes.
• Seedless vascular plants have drought resistant spores.
• Ferns have leaves that are called fronds. Fronds unroll as they grow.

Gymnosperms

Conifers, Cycads, Ginkgo, and Gnetophytes

• Gymnosperms do not have flowers.
• Gymnosperms do not have fruit.
• Gymnosperms do have seeds.
• Most gymnosperms are evergreen trees with needles and cones.
• Gymnosperms do not require water for fertilization. (The sperm do not need to swim through water to get to the eggs. Instead they are carried as pollen in the wind.)
• Pollen is made up of male gametophytes. Seeds contain female gametophytes.

Angiosperms

Flowering Plants

• Angiosperms have seeds, flowers and fruit.
• The fruit often helps spread the seeds.
• Seeds are spread when they pass through animals who have eaten the fruit they were in. Seeds can also be spread by the wind or water.
• Water is not required for fertilization. (The sperm don't need to swim to water to reach the eggs.)
• Seeds have stored food within them. This stored food is called endosperm.
• Angiosperms are divided into two groups: monocots and dicots.

Monocots

Flowering plants that have seeds with only 1 seed leaf.

• Monocots usually have flowers that have petals in multiples of 3.
• Monocots often have long, skinny leaves.
• Their veins run parallel to one another.
• Examples include: corn, grass, asparagus, tulips, crocus, and sunflowers.

Dicots

Flowering plants with two seed leaves.

• Dicots also usually have flowers with petals in multiples of 2, 4, and 5.
• The veins of dicots are branching, rather than parallel.
• Examples include: broccoli, cabbage, peas, peanuts, peaches, apples, roses, beans, and tomatoes.

Seeds

A seed contains the embryo (or baby) of a new plant.

• Seeds have a protective seed coat which protects the plant embryo inside it. Without this seed coat, the embryo might dry out.
• Most seeds have a food supply within them to feed the new plant as it starts to grow.
• Many seeds have structures that help them be spread by the wind, water, or animals.
• Most seeds will only sprout when conditions in the environment are favorable for their growth.