NEET-XI-Biology
05: Morphology of Flowering Plants
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- #5-dZygomorphicAns : Zygomorphic
Zygomorphic flowers are those flowers which can be divided into two similar halves by a single vertical plane. Examples of these flowers include pea and beans.
- #5-eSuperior ovaryAns : Superior ovary
Superior ovary flowers are those flowers in which the gynoecium is present at the highest position, while other floral parts are arranged below it. A flower with this arrangement is described as hypogynous. Examples include brinjal and mustard.
- #5-fPerigynous flowerAns : Perigynous flower
In perigynous flowers, the gynoecium is present in the centre and the rest of the floral parts are arranged at the rim of the thalamus at the same level. Examples include plum and rose.
- #5-gEpipetalous StamenAns : Epipetalous Stamen
Epipetalous stamens are stamens attached to the petals. They are found in brinjal.
- Qstn #6Differentiate between
Ans :Racemose inflorescence
Cymose inflorescence
1) Younger flowers are present at the tip while older flowers are arranged at the base of this inflorescence. Such an arrangement is called acropetal succession.2) The main axis in racemose inflorescence continues to grow and produce flowers laterally. 1) Younger flowers are present at the base of the inflorescence, while older flowers are present at the top. Such an arrangement is called basipetal succession.2) The main axis in cymose inflorescence has limited growth, which later terminates into a flower.
Fibrous root
Adventitious root
1) In monocots, the primary root which develops from the radicle of the seed is short-lived and is replaced by a large number of roots arising from the base of the stem.2) It is found in wheat and other cereals. 1) These roots arise from any part of the plant other than the radicle of seeds.2) It is found in banyan, Monstera, and other plants.
Apocarpous ovary
Syncarpous ovary
1) The flowers with apocarpus ovary have more than one carpel. These carpels are free.2) It is found in lotus and rose flowers. 1) The flowers with syncarpous ovary have more than one carpel. However, these carpels are fused.2) It is found in the flowers of tomato and mustard.
- #6-aRacemose and cymose inflorescence
- #6-bFibrous roots and adventitious roots
- #6-cApocarpous and syncarpous ovary
- Qstn #8Describe modifications of stem with suitable examples
Ans : Stems of various plants have undergone modifications to perform different functions.
Underground stems or storage stems:
Examples: Rhizomes, Corms, tubers
In ginger and banana, the underground stem is called a rhizome. The underground stem in Colocasia (arvi) is known as corm. Rhizomes and corms are underground stems, modified for the storage of food. Also, these stems help in vegetative reproduction of these plants. The tips of the underground stem in potato plants become swollen due to the accumulation of food. The potato is a tuber that helps in the storage of food and bears eyes on it. Subtended by a leaf scar, these eyes bear buds that give rise to new plants.
Supportive stems
Example: tendril
The stem in some weak plants bear thin, slender, and spirally-coiled structures called tendrils that help the plant get attached to nearby structures for support. Tendrils are found in cucumbers, melons, and other members of the family Cucurbitaceae.
Protective stems
Example: Thorns
The stem in bougainvillea and citrus plants (like lemon and orange) bear sharp, pointed structures called thorns, which provide protection to the plant from herbivores.
Photosynthetic stems
Example: Opuntia
The stem in the Opuntia is green. It carries out the process of photosynthesis in the absence of leaves.
Others stem modifications
In some plants, underground stems such as grasses spread in the soil and help in perenation. These stems are called runners.
The short lateral stem called the offset in some aquatic plants (such as Eichhornia) bears leaves and tufts of roots at the node and gives rise to new plants.
- Qstn #9Take one flower each of families Fabaceae and Solanaceae and write its semi-technical description. Also draw their floral diagrams after studying them.
Ans : (1)
Family Fabaceae/Papilionaceae (pea plant)
Fabaceae/Papilionaceae is a sub-family of the Leguminoseae family.
Vegetative features:
Habit: Pinnately compound, alternately arranged with leaf tendrils with the pulvinus present at the leaf base along folacious stipules.
Root: Tap root system with root nodules.
Floral features:
Inflorescence: Racemose, generally axial than terminal
Flower: Zygomorphic and bisexual flowers are found
Calyx: It contains five sepals which are gamosepalous while aestivation is imbricate.
Corolla: It contains five petals (polypetalous) with vexillary aestivation.
Androecium: It consists of ten anthers that are diadelphous with dithecous anthers.
Gynoecium: Monocarpellary superior ovary which is unilocular with marginal placentation.
Fruit: Legume pod with non-endospermic seeds
Floral formula:
Economic importance: Peas are used as vegetables for making various culinary preparations.
(2)
Flowers of Solanum nigrum
Family Solanaceae
Vegetative features:
Habit: Erect, herbaceous plant
Leaves: Simple, exstipulate leaves with reticulate venation
Stem: Erect stem with numerous branches.
Floral features:
Inflorescence: Solitary and axillary
Flowers: Actinomorphic, bisexual flowers
Calyx: Calyx is composed of five sepals that are united and persistent. Aestivation is valvate.
Corolla: Corolla consists of five united petals with valvate aestivation.
Androecium: It consists of five epipetalous stamens.
Gynoecium: It consists of bicarpellary syncarpous superior ovary with axile placentation.
Fruits: Berry
Seeds: Numerous, endospermous
Floral formula:
Economic importance: Used for medicinal purposes.
- Qstn #10Describe the various types of placentations found in flowering plants.
Ans : Placentation refers to the arrangement of ovules inside the ovary. It is of five basic types.
(A) Marginal placentation:
The ovary in which the placenta forms a ridge along the ventral suture of the ovary and the ovules develop on two separate rows is known to have marginal placentation. This type of placentation is found in peas.
(B) Parietal placentation
When the ovules develop on the inner walls of the ovary, the ovary is said to have parietal placentation.
C) Axile placentation
In axile placentation, the placenta is axial and ovules are attached to it. Examples include China rose, lemon, and tomato.
(D) Basal placentation
The ovary in which the placenta develops from its base and a single ovule is found attached to the base is said to have basal placentation. It is found in marigold and sunflower.
(E) Free central placentation
In free central placentation, the ovules develop on the central axis while the septa are absent. This type of placentation is found in Dianthus and primrose.
- Qstn #11What is a flower? Describe the parts of a typical angiosperm flower?
Ans : A flower can be defined as the reproductive unit of any flowering plant (angiosperms). Flowers carry out sexual reproduction in angiosperms. A typical flower is a modified stem with a condensed axis. A flower has four different parts i.e., the calyx, corolla, androecium, and gynoecium. Androecium and gynoecium represent the male and female reproductive organs of a flower (respectively). Bisexual flowers are those which contain both androecium and gynoecium, while unisexual flowers contain either gynoecium or androecium. The corolla and the calyx are generally distinct, but may sometimes be fused (called perianth). A flower that contains all four floral parts is called a complete flower.
Parts of flowers
(A) The calyx forms the outermost whorl of a flower, which contains sepals. They are green, leaf-like structures that cover and protect the flowers during the bud stage. When the sepals of a flower are free, they are called polysepalous, while fused sepals of a flower are called gamosepalous.
(B) The corolla of a flower is a layer that lies inside the calyx. It contains beautifully coloured petals, which help in attracting insects for pollination. When the petals are free, they are called polypetalous, while fused petals are called gamopetalous.
(C) The androecium or the stamen is the male reproductive part of a flower. It consists of two parts, the filament and the bilobed anther. The bilobed anther is the site for meiosis and the generation of pollen grains.
(D) Gynoecium represents the female reproductive part of a flower. It consists of an ovary. The ovary is connected by a long tube (called style) to the stigma. The ovary bears numerous ovules attached to the placenta.