Lecture 1

VASCULAR PLANT MORPHOLOGY

Learning outcome: i.

To identify plants by their taxonomical characteristics.

ii. To list down the importance of studying plants. iii. To state that plant morphology is an important tools in studying plants. iv. To differentiate between vascular plants, seed plants, non-flowering plants and flowering plants. v. To describe the diversity of seed plants. vi. To differentiate between monocots and dicots vii. To describe the diversity of flowering plants xi. To differentiate between the root system and the

What are the characteristics of plants? • • • • • • • •

multicellular non-motile eukaryotic cell walls comprised of cellulose autotrophic exhibits alternation of generations has a distinctive diploid (sporophyte) and haploid (gametophyte) phase.

Why study plants? We are dependent on plants in many ways. • food • air • materials (fibres) used in clothing • source (coal)

of

energy

• building materials • medicines and other chemicals

• moderate our climate by increasing rainfall, buffering wind • help control soil salinity and erosion • an important aesthetic value.

Plant morphology • study of the external structure or form of plants • studies the diversity in forms, with the naked eye or slight optical magnification • concerning various growth forms that plants take and how such morphologies contribute to the success of each species. • served largely as a handmaiden for systematics

Seed plants •

Vascular plants that produce seeds, which include: Gymnosperms (plants with naked seed)

Bristle cone pinesthe oldest trees

Giant Redwoods the tallest trees

Angiosperms (flowering plants)

• major types of vegetation found on land. • seeds help disperse plants and are able to survive the harshest conditions. Some can survive for years waiting for just the right conditions to sprout.

• Seed plants have stems, true roots, and leaves with a cuticle and stomata for aerial gas exchange. Most have non-flagellated or non-motile sperm and require other pollination vectors such as wind, insects, or birds. • The sporophyte is the larger, dominant generation which maintains itself by photosynthesis and nutrient uptake. The gametophyte, however, is greatly reduced and nutritionally dependent on the sporophyte.

Flowering Plants •

Comprise about 90 percent of the Kingdom Plantae.

•

The total number of described species exceeds 230,000, and many tropical species are as yet unnamed.

•

During the past 130 million years, flowering plants have colonized practically every conceivable habitat on earth: deserts, alpine, grasslands, freshwater marshes, dense forests and mountain meadows as well as aquatic habitats.

Flowering Plants • Produce flowers and seed-bearing fruits. • Represent an extraordinary diverse group of life forms. They come in variety of shapes and sizes: • Minute plants: Wolffia globosa - less than a millimeter (1/25th of an inch) long. • Giant trees: Eucalyptus regnans - over 300 feet (100 m) tall. Although the current record-holder for tallest tree is actually a 367 foot (112 m) conifer called the California redwood (Sequoia sempervirens).

Flowering Plants Adansonia digitata - a South African baobab tree, one of the most massive flowering plants. The enormous trunk may exceed 100 feet in circumference and store 25,000 gallons of water weighing 100 tons

Flowering Plants

The evolution of the flowering plants split them into two major groups - the monocotyledonous plants (monocots) and dicotyledonous plants (dicots). Most angiosperms are dicotyledonous. There are several characteristics which separate these two groups.

Monocots

Dicots

Cotyledon

1

2

Floral Arrangement

3's

4's and 5's

Leaf Venation

Parallel

Net

Vascular bundles

Scattered

Ring

Habit

Herbaceous

Herbaceous + Woody

Roots

Fibrous

Taproot

Pollen grain

1 pore

3 pores

Growth

Primary only

Primary and Secondary

Examples:

Grass, Palm, Orchid

Oaks, Roses, Sunflowers

Diversity of Seed Plants The following body plans are recognized:Herb - non-woody, small plant Shrub - woody, multi-trunked plant Tree - woody, single-trunked plant Vine - twining or climbing plant

Several variations to the different body plans Lianas woody vines of tropical forests - rooted in the ground, spreading over the canopy.

Epiphytes - plants rooted on other plants (but not parasitizing these), simply using the other plant as a foot hold to get into the light. e.g. members of the pineapple (Bromeliad), orchid, and anthurium (Aroid) families

Giant herbs - bananas, some gingers and heliconias grow to a considerable height without woodiness or even a true stem. What appears to be the trunk is actually the leaf bases, wrapped one around the next. The banana "tree" is one such giant herb.

Aloe pillansii in South Africa

Arborescent monocots - some woody monocots (e.g. species of Yucca, Dracaena, Pandanus, Agave) have secondary growth but quite different to that found in dicots. An outer ring of dividing cells produces on the inside new parenchyma with scattered vascular bundles.

Palms - just below the apical mersitem, a second (primary thickening) meristem develops which broadens the growing point. This very broad stem then simply elongates, with vascular bundles and fibres at the periphery lending strength to the palm trunk.

Bamboos - are woody grasses which attain, in some cases, tree-like stature. Their strength is due to the large numbers of vascular bundles and fibres in the stem periphery, the central pith eventually dying. Bamboos grow extremely rapidly but reach a finite height (determinate growth). New shoots then emerge from the underground stem (rhizome).

Based on their morphological adaptations and modes of life. Seed plants are categorized into 5 groups: 1. 2. 3. 4. 5.

Epiphyte Parasitic plants Creepers Aquatic plants Free-living plants Based on the availability of water, seed plants are categorized into 3 groups: 1. Xerophyte 2. Hydrophyte 3. Mesophyte

THE PLANT BODY The plant body is divided into: The Shoot system – aboveground system -- stem, leaves, flowers, buds, fruits. The Root system – underground system – roots Both systems depend on one another. Materials travel between the shoot and roots in the vascular system.