Plant Diversity Adaptations for life on land

Adaptations for Life on Land Life on land presents problems not seen in aquatic habitats. These include:  Avoiding drying out  Getting adequate water  Getting sperm to eggs without water  Becoming tall  Distributing water and food within the plant

Plant Adaptations for Life on Land Waxy cuticle: a waterproof coating on outside Vascular tissue: plant “plumbing” to distribute food and water Xylem for water, Phloem for food. Blue lines represent vascular tissue Xylem on left, Phloem on right

Plant Adaptations for Life on Land Roots: to absorb water, anchor the plant Leaves with stomata: photosynthetic surfaces. Stomata are holes in the leaf that can open and close Pollen and seeds: reproductive adaptations Flowers: reproductive adaptations

In this show We will look at the major plant phyla, starting with those that appear in oldest fossils. We will see that each phylum has some adaptations for life on land, few have all. Plants moved to land over 400 million years ago and are the first land dwelling organisms.

Liverworts

Most primitive land plants No vascular tissue Must live in very wet environment Depend on water for reproduction (swimming sperm) Have cuticle, leaves

Mosses

There are haploid male and female moss plants (the green parts) that make gametes Swimming sperm. Simple vascular tissue (xylem only) Waxy cuticle Leaves Simple roots

Ferns

First complete vascular tissue (has both xylem and phloem) True stems No flowers, seeds, fruits Swimming sperm Has waxy cuticle, leaves, roots

Devonian Ferns – Dinosaur times 250 mya Their vascular tissue allowed them to grow up to 90 feet tall. These were major forest plants. Their fossilized remains became coal in many places.

Gymnosperms – First Seeds, first pollen, no flowers, no fruits

Gymnosperms Male and female cones NOT dependent on water to reproduce Naked (gym) seeds in the petals of female cone Often needle bearing Often “evergreen” (except cypress trees, tamaracs, gingko)

Female cones

Male pine cones releasing pollen Male cones are usually so small that they are not noticed (about 1-2 cm long). Pollen is produced in these cones.

Ginko – the gymnosperm without needles Ginkos are some of the most ancient types of trees, Originally from China There are male and female trees The stinky “fruit” is really not a fruit. It’s a soft seed.

Angiosperms- Flowers and Fruits

Angiosperms Angiosperms are the only phylum with all the adaptations for life on land listed earlier in this show. They are currently the most plentiful kinds of plants on the planet. Human food consists largely of angiosperms (grains, beans, fruits, vegetables, nuts). There are two big sub-groups of Angiosperms: monocots and dicots

Monocots : Grasses, grains, lilies Monocots have spear shaped leaves, with veins of vascular tissue that run in parallel lines. The palm is the only monocot tree.

Dicots: seeds with 2 halves Their leaves have veins that look like “nets.” an often the leaves are broad. Most angiosperm trees are dicots.

Comparing Monocot vs. Dicot seeds

Monocot vs. Dicot leaves, seedlings

Summing Up Examine your charts of the phyla of plants and notice the trends. What features do all land plants have? Which adaptations do only a few have? Which phyla are the first to show each adaptation? All of these phyla live successfully on land, although some must live near water or moisture. Two phyla are independent of water for reproduction. Name them. Why do you suppose plants with fruits and flowers are the most common kind of plants on land (think of the advantages of their adaptations)?