Lower vascular plants:-
The plants which are not differentiated into root, stem and leaves and lack vascular system and have no tissues like Xylem and Phloem are called as lower vascular plants. The lower plants are small in size than higher plants. These plants can reproduce by means of spores. As lower plants have no definite roots so, they absorb water by diffusion and osmosis. Like higher plants the lower plants have no stomata on their body for the purpose of gas exchange.
1.1 Habitat of lower plants:-
The lower plants can not complete their life cycle without water so, they must require water for the survival. So, they mostly present on shady, damt and wet places. The lower plants lack vascular tissues. So, they cannot store water in their cell body So, They cannot survive in the shortage of water. Some lower plants such as “poikilohydric” survive in dehydration conditions.
1.2 Morphology of lower plants:-
The lower plants are small in size so, they have no complex structure. They lack vascular system or tissues which involves in vascular system such as Xylem and Phloem. They have no true leaves, they have leaf like structures which have chlorophyll for the purpose of photosynthesis. They have no true stem. The lower plants have some filaments similar to roots which help the plant body to anchor into the soil. Their body consists of thallus. A thallus is a structure which is not differentiated into stem, roots and leaves.
1.3 Anatomy of lower plants:-
The lower plants have simple arrangement of cells. These are simpler plants. The lower plants have no true leaves. The structure which contains chlorophyll is present which acts as artificial leaves. They have one single layer of cells. The food is also prepared in these structures and transported to the body. They have no definite vascular system for transportation.The lower plants have no stem. The lower plant such as fungi consists of a hyphae which may be septate or aseptate. The hyphae accumulate and form a thallus body. The mycelium forms a mass of tissues known as fungal tissues. They are of two types as Prosenchyma and Pseudoparenchyma.
1.4 Reproduction or life cycle of lower plants:-
The lower plants reproduce by three methods such as:
In asexual reproduction sexes are not involved. It carries by designed reproductive units known as spores. Several types of spores are as follows:
Endo or Exo spores
In this process a new individual evolve from the parent individual when a cell or group of cell apart from parent body it is called as vegetative propagation.
This type of multiplication can be carried out by following ways such as:
The sexual reproduction contains the union of two haploid cells known as gametes which unite to form a diploidal zygote. This phenomena of uniting is known as fertilization.
Alternation of generation:
The lower plants have life cycle which consists of two parts called as alternation of generations. It is also known as metagenesis and heterogenesis. In the asexual sporophytic stage the spores are produced and in gametophytic stage the sperms and eggs are produced. The lower plants have two categories some are monoecious and some are dioecious.
First, the male and female spores are produced on same plant body and are called as “microspores” and “megaspores” respectively. Later they produce on different plant bodies.
Requirement of water for reproduction:-
In the life cycle of lower plants the gametophyte stage is the prominent or dominant. During this stage the water is required for the swimming of sperm toward egg and then fertilization occurs. That’s why lower plants prefer humid and moist environment for reproduction purpose. In dry weather the sperms search for rain and water.
Examples of lower plants:-
The lower plants consists of several groups such as
They have chlorophyllus plants like body and undergoes the process of photosynthesis.
They are simple organisms.
Example: Algae consists of a large group of members such as
They require water for reproduction so, are called as amphibias plants. Their habitat is shady places and moist environment/
Their phyla are as follows.
Higher vascular plants:
For the transportation of food, water and minerals. The plants have some special tubular tissues such as Xylem and Phloem. These plants are known as higher plants.
The higher plants are large in size in comparison with lower plants. The higher plants reproduce by process of seed germination. These plants can absorb water by their large network of roots through the process of osmosis. The higher plants have stomata on the leaves of gas exchange.
For example: true ferns, conifers and flowering plants.
2.1 Habitat of higher plants:-
The higher plants are terrestrial Xerophytes and some are epiphytes on the basis of several groups such as pteridophytes and gymnosperms. The higher plants have vast range of habitats.
The pteridophytes can grow on land like terrestrial environment. Some are aquatic which require water for survival and other are Xerophytes such as selaginella these can survive in hydrated areas where water supply is insufficient. The gymnosperms present in arctic zones and tropical zones. Some are xerophytes but gymnosperms are not epiphytes.
2.2 Morphology of higher plants:-
The study of vegetative structures and reproductive structures of plants is called as morphology. The higher plants have two major organ systems such as root system ant shoot system which consists of roots as well as stems and leaves respectively. The reproductive structures are many and they vary from one plant species to another. These structures are flowers and fruits which are present in angiosperms. The conifers consist of seed cones and ferns have “sori” for reproduction purpose.
Leaves contain chlorophyll for the process of photosynthesis by which higher plants prepare their food such as carbohydrates and other nutrients. The leaves have stomata’s openings for gas exchange and transpiration. The stem consists of nodes and internodes on which leaves are attached. The outer layer of stem helps in protection and gas exchange.
The roots of higher plants are complex and have many types such as tap roots or adventitious roots. They absorb minerals and water from the soil. Some roots play importance role in nitrogen fixation.
2.3 Anatomy of higher plants:-
The study of plant tissues and cells to know the way of working of plants and their way of construction is known as anatomy. There is complexity in the arrangement of vascular tissues in higher plants. The different parts of a higher plant are as follows:
They have complicated leaf structure. A waxy layer which is known as cuticle is present to lowers down the dryness. To control the transpiration, stomata are present in the epidermis. The vascular tissues are present inside the parenchyma which act as the carriers of food body. The ancient fossil of pteridophyta such as “Rhynia” was leafless.
In pteridophytes two types of leaves are present such as
The stem of higher plants consists of many layers. The outer layer is more functional. The phenomena of gas exchange, protection and photosynthesis is performed by this outer layer. The bark act as outer layer in woody plants and it has dead tissues. The layer which is inner to the outer layer is known as parenchyma. The middle layer is the layer of tissues which has function in vascular system which provides food and support. The cortex consists of several parts such as
The stele is also present with pith absence Xylem and Phloem are also present in the middle of endodermis. The Xylem is present in the centre and the Phloem surrounded the Xylem.
The structure is literally same as stem structure. The vascular tissues are present in higher plants are known as stele and have many types of arrangements in roots. The siphonostele is present in the higher plants. The Xylem consists of parenchyma. Roots hairs also originate from outer covering called as epidermis under the epidermis, cortex is situated. The xylem is present in the centre and surrounded by phloem.
2.4 Reproduction or Life cycle of higher plants:-
The higher plants can reproduce by several methods such as:
righttop The reproduction in which buds are formed which have food storage. They have ability to grow a new plant. There buds are known as bulbils.
Example: Cycas reproduce by means of vegetative reproduction.
The higher plants also have reproductive units known as spore which produced in sporangia. The sporangia have different shape size arrangement and ways of development in many groups of pteridophytes. The cryptogams spore producesing plants are classified on the basis of this character. The origin of sporangia is stem. The sporangia are present on leaf like from known as “sporophyll”. The spores having different shape and function are called as “Heterospory”. The megaspores are larger than microspores. The gymnosperms are also heterospores they posses both types of spores both the spores are haploid. The microsporangia is the site of production of microspores. The sporangia are presents on sporophaylls. They may be micro or mega (sporophylls). The sporophylls form a untied cone like structure known as “strobillus”. The strobillus are of two types “Male strobili” and “female strobili” the angiosperms are diploid and also have micro and mega spores.
On germination the haploid monoecious are diecious gametophytes are produced by spores. Then these gametophytes make sixual contact and give rise to new gametophytes. The gametophyte is the site on which sex organs are present the gametophyte may be Exosporic or endosoric. The sex organs consist of sperms and eggs. The sperms are moveable due to presence of flagella and eggs are immoveable. The sex organs the gametangia are of two types such as:
Anthredium (male gametangium)
Archegonium (female gametangium)
The gymnosperms have uncovered ovules so pollination is the transfer of male gametophyte to the ovule. Some specialized structure are present on seed plants for the joining of male and female by a process known as “fertilization”. After fertilization an embryo is formed in the seed. The seed acts as protective sheild and provide food to the embryo then seed is released by plant and it germinates to form another plant body. The seed plants are divided into two groups such as:
Plants with cones
The flowers are structures of plant that have function in reproduction. It has male and female parts pollen and ovules respectively.
Some members are as under Pteridophytes: The pteridophytes have no seeds.
They have two phyla such as:
These are vascular plant and consists of naked seeds. The ovaries are not covered.
The gymnosperms have four phyla as:
The seed plants are known as angiosperms. They have two main classes:
Evolution of lower and higher plants:-
The plants consist of many cells and are able to live on land. The number of plants prepares their food by photosynthesis but other organisms like some bacteria and protists are also having ability to perform photosynthesis. As algae are unicellular and have diloruphyll. The green algae lives in fresh water have linkage to the plants called as charophytes. They evolved from algae. The bryophytes are also land plants but they do not have vascular system so, they cannot become tall like trees. As bryophytes lack stomata but one member of it has stomata. Hornworts and mosses have stomata so it is considered that vascular plants are evolved from bryophytes. So, vascular plants have ancestral relationship with hornworts and mosses.
right5558790The first fossil of higher plants was searched in rocks about 425 million years ago “Aglaophyton” is the ancient plant. The aged plant has been linked with bryophytes called as prototracheophytes. Two important features of early higher plants are as follows which make them advance plants. They have efficient vascular system to transport the food and water. Secondly they can prepare lignin which makes the tissues of vascular system adamant and hard. The higher plants have evolved from algae and bryophytes in some aspects such as: The pteridophytes are evolved from algae due to isomorphic alternation of generation. The bryophytes and pteridophytes have same terrestrial habitat. They have heteromorphic alternation of generation.
Fig: Evolution of lower and higher plants