Scientific study of plants is called Botany or Phytology. Plants are considered producers of planet Earth. The kingdom
Plantae can be broadly classified into two groups, namely Cryptogams/Non-flowering plants and Phanerogams/Flowering plants. The examples
of plantae kingdom include Mosses, Fern, Mango, etc. Plants are called autotrophs, as they produce their food on their own by the process of
photosynthesis. In desert trees, stems carry out photosynthesis. Theophrastus is called the Father of Botany.
Classification of Cryptogams
Cryptos means hidden and gamos means sex organs. Cryptogams don't produce seeds. Instead they produce spores, which are primitive forms of
seeds. Hence Cryptogams are known as Spore plants.
Cryptogams are further divided into 3 groups,
- They are primitive of all plants. Plants of this group are commonly known as Algae. Algae constitute majority of vegetation on planet Earth.
They are dominant in both land and water. Algae are present in ponds, lakes, moist rocks, on other plants, etc.
- Study of Algae is called Algology or Phycology. Algae have a simpler plant body i.e. Thallus (no root, no stem), which is not differentiated
into root, stem and leaves.
- Algae are of 3 types, (i) Green Algae, which have chlorophyll pigment and starch as reserve food, (ii) Brown Algae, which have Fucoxanthin
pigment and Laminarin (sugar) and Mannitol (alcohol) as reserve food and (iii) Red Algae, which have Phycoerythrin pigment and Floridean starch
as reserve food.
- Chlorella is the green algae used as source of Oxygen in space. Rhodomela and Polysiphonia are red algae from which Bromine is extracted
commercially. Laminaria is brown algae from which Iodine is extracted commercially.
- Many Algae are edible, e.g. Chlorella (rich in protein equivalent to Soyabean), Chondrus, Porphyra, etc. Japan has exploited seafood mostly.
They take algae as food.
- Large brown algae in the sea are known as Sea Kelps. Gelidium and Gracilaria are red algae from which the solidifying agent Agar (used in
jams and jellies) is obtained.
- Red color of Red Sea is due to predominance of the algae, Trichodesmium.
- They are the first plants to come out on land. So, they are the amphibians of the plant kingdom. They require water and land for completing
their life cycle. Examples of Bryophytes are Funaria, Anthoceros, Marchantia, etc.
- They are the first embryophytes. Embryo development is present in these plants. They are restricted to wetlands and margins of water bodies.
- Bryophytes have more ecological value. They prevent soil erosion and recharge the ground water because of their high water holding capacity.
They make the wetlands and other habitations suitable for the survival of many other plants and animals.
- Bryophytes are used to pack and transport nursery plants because of their high water holding capacity. Bryophytes have no roots but have a
root like structures known as Rhizoids.
- Bryophytes are of 3 types, (i) Mosses, (ii) Hornworts and (iii) Liverworts.
- They have two types of sex organs, Antheridia, the Male sex organ and Archegonia, the Female sex organ.
- They are the first true terrestrial plants. They are commonly known as Feather plants as their leaves appear like feathers.
- Ferns constitute major Pteridophytes. Ferns are used as ornamental plants. Other examples of Pteridophytes are Club Mosses, Horse Tails,
Selaginella, Adiantum, Equisetum, etc.
- They are the first plants to develop vascular tissues or they are the first vascular plants. There are 2 types of vascular tissues, Xylem
for carrying water and Phloem for carrying food.
Classification of Phanerogams
Phaneros means visible and gamos means sex organs. Phanerogams are propagated by seeds. Hence, they are known as seed plants or
Spermatophytes. Phanerogams are further classified into two groups, Gymnosperms and Angiosperms.
- Gymnos means naked and Sperms means seeds. They have seeds but they don't bear fruits. True flowers are are absent in Gymnosperms.
- They appear to exhibit coniferous habit. They are restricted to mountainous and temperate regions. They are the tallest plants of
- Examples of Gymnosperms are Sequoia sempervirens (Redwood tree of California, 120m), Pine, Chir, Fir (these 3 are Christmas Trees), Spruce,
Willow (used in Cricket bats), Ginseng (used in many medicines), Cycas, Ginkgo, etc. Cycas and Gingko are considered living fossils.
- Angios means Sac. They are the dominant vegetation on land. They are highly evolved plants. They are both terrestrial and aquatic.
- They have cotyledons, which store food for the embryo while developing into plant. Based on number of cotyledons in the seed, Angiosperms
are of two types, (i) Monocotyledons, which have 1 cotyledon in their seeds, e.g. Coconut, all types of grasses and (ii) Dicotyledons, which
have 2 cotyledons in their seeds, e.g. Mango, Cashew, etc.
- Angiosperms exhibit typical plant structure. Plant body is divided into two parts, (i) Underground root system and (ii) Aerial shoot system.
Plants Based on their Habitat
The nomenclature of plants based on their habitat is given below,
- Plants in typical tropical conditions - Mesophytes
- Deserts - Xerophytes
- Sand - Psammophytes
- Rock – Lithophytes
- Water - Hydrophytes
- Saline soils - Halophytes
- Acidic soils - Oxylophytes
- Snow - Psychrophytes
- On other plants - Epiphytes
- Shade - Sciophytes