UNIT 4 KINGDOM PLANTAEBOTANY : The study of plant physiology, plant anatomy, plant morphology, plant taxonomy; including plant genetics, ecology and cytology.

PLANTAE: A TRUE PLANT IS A MULTICELLULAR AUTOTROPHIC TERRESTRIAL ORGANISM THAT POSSESSES CHLOROPHYLL “a” AND “b” CONTAINED IN CHLOROPLASTS AND SHOWS STRUCTURAL DIFFERENTIATION – with true roots, stems and leaves.

Some taxanomic systems consider some of the most primitive plants not to belong to kingdom plantae at all. Instead they throw these organisms into Kingdom Protista. For example: Some algae are multicellular, autotrophic, possess chlorophyll “a” and “b”, terrestrial and show structural differentiation. The majority are aquatic, none of them possess vascular roots, stems and leaves. Where do we put them? Are they a multicellular protist or a very simple type of plant?

ALGAE

Multicellular Protist or Primitive Aquatic Plant?

Cyanobacteria

Plant-like Protists

Algae

Algal Characteristics• Vary in size from nanoplankton

(< 2 µm cyanobacteria ) to Giant kelps (> 70 m long). Possess a cell wall.

• Contain pigments • chlorophylls a, and many

often have another chlorophyll, like b, c, or d and accessory red, blue and brown photosynthetic pigments

Algae - What are they?

• Primitive plants • No true roots, only attachment

structures (Holdfasts)• Produce spores (not seeds)–

motile or non-motile• Most have sexual and asexual

reproduction• Non-vascular, do not possess

an internal transport system.

Algae vs. ‘REAL’ plants

Similarities and differences: • Both are photoautotrophic• Similar metabolic functions to higher

plants eg. photosynthesis• different anatomical structures,

reproductive structures.• different reproduction.• No true roots, stems leaves.• Non-vascular, therefore nutrient uptake

over surface. And wastes washed away from surface by aquatic environment

Classification - a few Algal Phyla • Cyanophyta: Blue-green or Cyanobacteria.

         Prokaryotic. Marine, FW and terrestrial.

• Pyrrophyta, Chrysophyta, Euglenophyta: Marine and FW

phytoplankton – Photosynthetic Protists.

KINGDOM PLANTAE:

• Rhodophyta: Red algae. Mostly marine.

• Phaeophyta: Brown algae. Mostly marine.

• Chlorophyta: Green algae. Marine, FW and terrestrial.

The role of these pigments is to absorb light

- In water the problem is that red and violet wavelengths do not penetrate the vertical column very well. So Chlorophylls do not work well at greater depths. Algae that inhabit greater depths do so with the help of accessory pigments, these algae take on a variety of colours.

-Chlorophyta – Contain Chlorophyll a + b. So green wavelengths reflect. They store their products of photosynthesis as starch.- Phaeophyta – Contain Chlorophylls a + c as well as an accessory pigment Fucoxanthin. So yellow and brown wavelengths reflect. Store food as starch and as oil.

Rhodophyta - Contain Chlorophyll a + (d) as well as accessory pigment Phycobillins. These phycobillins are specialized for absorbing blue light, which allows them to inhabit the deepest depths.

Where do Algae live?

Marine habitats: • seaweeds, phytoplankton

Freshwater habitats: • streams, rivers, lakes

and ponds

Terrestrial habitats: • stone walls, tree bark,

leaves, in lichens, on snow

Marine Biomes

Freshwater habitats

Terrestrial habitats

How do algae function?Photoautotrophs: 6C02 + 6H20

C6H1206 + O2 • use carbon, light, and water • produce chemical energy

(carbohydrates) and produce O2 as a by-product.

• Basic storage products: carbohydrates as starch or converted to fats as oil

• Require nutrients: N, P and minerals.

Why are ALGAE important? Ecological importance of algae a) Production of Oxygen as ‘by-

product’ of photosynthesis:• All aerobic heterotrophic organisms

require O2, • e.g. fungi and animals need O2, to

run cellular respiration to stay alive

b) Production of biomass: • autotrophic organisms - represent the base of the food

chain/web, particularly in aquatic environments.

Algal diversity• Algae ARE NOT a single phylogenetic grouping,

but give rise to several independent evolutionary lines. Our focus is on “CHLOROPHYTA” as it is believed to give rise to the terrestrial plants.

• Very diverse, very well adapted to certain environments, • Range from unicellular, colonial

multicellular• e.g. marine, freshwater, terrestrial; • often extreme habitats• CHLOROPHYTES share Similarities to true

plants – Same two chlorophylls a and b, Store products of photosynthesis as starch, cell wall primarily made of cellulose.

Algal construction types : Morphology

1. Unicellular algae

2. Colonies

3. Filaments

4. Multicellular

Unicellular algae• ‘Microalgae’ - some may form colonies

Algal coloniese.g. Chlorophyta: Volvox (Order Volvocales) - 500-5000 cells per colony. - Colonies spherical up to 1.5 mm diameter. - Individual cells surrounded by a mucilaginous sphere - marine and freshwater

http://www.youtube.com/watch?v=w8O4OolGcPg

Volvox colony – with Daughter colonies

Filamentous algae• Unbranched filaments

• Branched filaments• Different branches can have different

morphologies:

MULTICELLULAR - Macroscopic

Why are algae important?

• Primary producers, basis of food webs,

“FORESTS/GRASSES OF THE SEA”

• Pioneer Species: on rocky shores, mudflats,

hot springs, lichen communities, 'snow algae'

• O2 production and carbon fixation in aquatic

habitats.

• Rare autotrophic organisms in extreme

habitats.

Examples of ecological importance• Red tides, other algal blooms• Hot springs• Kelp forests• Rocky shore ecology• Aquaculture

Cyanobacterial bloom

Extreme halophytes

Uses of Seaweeds

• Present• Food• Hydrocolloids and some

chemical substances• Fertilizers

• Potential• Source of

energy/compost by digestion

• Waste-water treatment

Algae as human food • Annual value is about US$6 billion• Main market and production area is Asia• “Mariculture” has become very important• Main high-value species are ‘Nori’, ‘Kombu’ and

‘Wakame’ (Porphyra, Laminaria and Undaria)• Mainly used as a subsidiary food: adding relish, taste

and 'feel' to food• European and North American market presently very

small but has potential