Reproduction and Modification in Plants Online Test 7th Science Lesson 5 Questions in English

Explanation

The flowering plants have root, stem and leaves. They are called vegetative organs. Flowers, fruits
and seeds in a plant are called reproductive organs.

Explanation

The process by which plants and animals produce young ones and increase their number is known
as ‘reproduction’.

Explanation

Seed is produced from a flower by the process of pollination and fertilization. This is known as
sexual reproduction.

Explanation

Drumstick tree can be grown from both seeds and stem cuttings. When plants reproduced from
seeds, we call that process as sexual reproduction. All other ways of reproduction without seed are
called as asexual reproduction.

Explanation

Node is the part of stem.

Explanation

In a bud, we can see a green colour, leaf like structure which cover the whole bud or flower, each of
these green like structure present as an outermost layer is called as sepal.

Explanation

The outer most ring of sepals is known as calyx.

Explanation

Petals are the largest part of flowers. They are often attractive, brightly coloured, sometimes sweet
scented and attract the insects.

Explanation

The ring of petals together is called corolla.

Explanation

Inner to this corolla, in Hibiscus, we can observe a long tube on which many stamens are arranged.

Explanation

Inner to this corolla, in Hibiscus, we can observe a long tube on which many stamens are arranged.
But in Datura, we can see only five stalked structures, stamens. This ring or whorl of a flower is
called androecium.

Explanation

Each stamen consists of two parts – a stalk called filament and a lobe called anther. If you touch these lobes in a mature flower, we can get a powdery substance called pollen grains, male reproductive part.

Explanation

Inner to this androecium whorl, we can find a female reproductive part of the flower, called
Gynoecium.

Explanation

In Gynoecium you will find this part with a swollen bottom part. This is the ovary. Seeds are
produced in this part.

Explanation

On top of the ovary there is a slender tube-like structure called style.

Explanation

The top most sticky tip of the style is stigma. Pollen grains are received by the stigma. This is the
fourth whorl of a flower.

Explanation

A group of flowers arranged together is called inflorescence. Tridax procumbens, looks like a single
flower, but is an inflorescence. Leaf juice of this plant is used to cure wounds and cuts.

Explanation

The sunflower is not a single flower. It is a group of flowers clustered together. A group of flowers
arranged together is called inflorescence.

Explanation

If all the four whorls- calyx, corolla, stamens and pistil are present, then it is called as complete
flower. Complete flowers are bisexual flowers. If any of these four whorls is missing, then it is called
as an incomplete flower.

Explanation

The process by which pollen grains reach stigma is called as pollination. The flower that receives
pollen grains is called pollinated flower while the one that did not receive pollen grains is called as
unpollinated flower.

Explanation

In some plants like grasses, pollen grains are light. Stamens shed pollen grains, and are carried by wind to another flower. Insects, birds are also other agents of pollination. Bees, butterflies and variety of bird’s hover around flowers. They help to carry pollen from one flower to another. Pollen grains stick to their legs, wings or abdomen when they move from one flower to another. This is called as Cross pollination.

Explanation

Beans (Fabaceae), tomatoes (Solanaceae) are commonly self-pollinated. Even though, for example
tomato, self-pollinate, they need the help of the insects to create vibrations within the flowers that
will effectively loosen the pollen. Paddy is mostly self-pollinating using just gentle wind as the pollinating agent.

Explanation

The agents that are helping in pollination are called pollinators.

Explanation

When you shake stamens, pollen grains fallout. Thus, when a wind shakes the flower or when a butterfly agitates the flower, pollen grains could fall onto the stigma of same flower. Some plants that have both the male and female parts within a single flower (bisexual) pollinate by this means. This is called as Self-pollination.

Explanation

During the germination a tube develops from the pollen grain that carries male gametes that ultimately reaches female gamete inside the ovary through the style. Male gamete fuses with the female gamete to form zygote. This process is known as fertilization.

Explanation

Inside the ovary, small rounded structures, ovules are present. In these ovules, female gamete is
present.

Explanation

A green part above fruits of brinjal and lady’s finger are sepals of a flower. In some, after fertilization, sepal will not fall from fruit and remain or persist with fruit. In pea, fruit is not fleshy, but forms a covering pouch for many seeds.

Explanation

The post fertilization changes and are: 1. Calyx sometimes persist with fruit 2. Petals wither / fall
off 3. Androecium fall off. 4. Pistil remain and develops into a fruit. 5. Style and stigma fall off 6. Ovary enlarges to store food materials and develops into a fruit. 7. Ovules present inside the ovary develops into seeds.

Explanation

The world’s largest and heaviest seed is the double coconut. The seed looks like two coconut fused together. It only grows in two islands of the Seychelles. A single seed may be 12 inches long, nearly 3 feet in circumference and weighs about 18 kg.

Explanation

Orchids have the smallest seeds in the plant kingdom. 35 million seeds may weight only about 25 grams.

Explanation

Earlier we saw that plants reproduce not only from seeds but by other processes as well. The production of new plants without the involvement of pollination and fertilization is knows as
asexual reproduction.

Explanation

The types of asexual reproduction are 1. Vegetative Propagation, 2. Budding, 3. Fragmentation and
4. Spore formation.

Explanation

When we go to a bakery, we see so many types of cakes and breads. These are very soft in nature. This is due to the presence of Yeast.

Explanation

Single yeast undergoes asymmetric division. It produces a small protuberance which gradually
grows and detaches from the parent cell. This process is called budding.

Explanation

In a pond we see so many algae. Spirogyra is a filamentous alga, when it matures, the filament divides into pieces. Each fragment or piece of a filament will grow into a new filament or individual. Likewise, Spirogyra produces so many young ones and this process is known as fragmentation.

Explanation

In potato, shoot arise from eyes. Sugarcane, yam also grown like this. Vegetative parts of the plants
such as root, stem and leaves can help to propagate the plant. Corn does not undergo vegetative
propagation.

Explanation

Scarcity of water, high temperature, nutrient deficiency in soil etc., are unfavourable conditions. During these conditions non-flowering plants like Algae, Fungi, Moss and Ferns produces spores. They germinate into a new plant when favourable conditions are returns.

Explanation

Look at the part we usually consume as ‘carrot vegetable’. However, it is not an unripe fruit, but the
tap root of the carrot plant. We can see that the tap root of the carrot is swollen. In the case of the
carrot plant, the tap root has a different characteristic than the usual pants.

Explanation

What appear as the ‘leaf’ of a cacti are actually their stem and what appear as ‘spine’ on them are actually leaf. Its leaves are modified into spines, an adaptation to reduce transpiration. Photosynthesis is performed by the stem part of the plant.

Explanation

Look at a radish, turnip, beet root, and carrot. They all grow under the soil. As soon as you pluck it
from the ground if you wash them gently, you will notice small roots dangling from their surface. All these vegetables are in fact roots of the plant. Instead of thin slender roots, in case of such plants, the roots have become a place to store the food produced by them.

Explanation

One can notice that the tap root of radish is in the shape of spindle, swollen in the middle and
tapering at both ends. Such type of modified roots is called spindle shaped root.

Explanation

At times, like in the case of turnip, and beet root the tap root can acquire a shape of top, that is
spherical at the base and tapering shortly towards the apex. They are called as Top shaped root.

Explanation

In case of carrot, the shape is conical, broad at the apex and tapering gradually towards the base
and such modified roots are called Conical shaped root

Explanation

Look at a banyan tree. It seems to have many trunks supporting it. However, many of them are actually roots. As the banyan tree is large and huge, it needs support not to tilt and fall down. Many plants require such additional support. Such plants develop roots on their aerial parts to provide mechanical support. These roots grow downward and act as supportive organs.

Explanation

There are three types of modified roots for support. i. Prop roots, ii. Stilt roots and iii. Climbing roots.

Explanation

A root growing from a location other than the underground, such as from a stem or leaf is called as
adventitious root.

Explanation

Prop roots: Roots are modified to provide mechanical support as seen in Banyan tree. These roots grow vertically from horizontal branches of a tree.

Explanation

In sugar cane, and maize adventitious roots arise from the nodes in cluster at the base of the stem. These roots are called stilt roots which gives additional support.

Explanation

Climbing roots: In betel and black pepper, nodes or inter modes bear roots which help in climbing.

Explanation

The four types of modification of roots are 1. Roots for storage, 2. Mechanical Support, 3. Gaseous Exchange and 4. Roots for other vital function.

Explanation

Roots may also perform special function. Haustoria or Sucking roots, are one such example. Cuscuta a parasite plant, climb the trees and other vegetation and use the haustoria roots to penetrate the tissue of the host plant and suck nutrients from them. They are usually found in parasitic plants that depend on the host plants for nutrients.

Explanation

Vanda is an epiphytic plant, which grows on trees. The velamen tissue present in the epiphytic root, absorbs moisture, to perform photosynthesis.

Explanation

Avicennia is a tree which grows in mangroves or swamps. They have roots which are seen above the ground for the purpose of gaseous exchange. These roots are erect, peg like structures with numerous pores through which air circulates. These roots are called breathing roots, or
pneumatophores.

Explanation

Can you guess what is common between ginger, onion bulb, potatoes. All three are stems. Some plants have their stems modified for storing food and for vegetative propagation. Modified stem may be aerial, subaerial or underground stems.

Explanation

Stem of some plants remains sub – aerial which grow horizontally on the surface of the soil for the purpose of reproduction. There are four types. 1. Runner, 2. Stolon, 3. Sucker and 4. Offset.

Explanation

Runner: The stem grows laterally on the surface of the soil, breaks up to produce roots where it touches the ground to give rise to new plants. E.g: Centella (Vallarai).

Explanation

An offset is a short and thick branch that arises from the axial part of a leaf. It has thick internodes.
It produces a tuft of leaves and cluster of small roots below. E.g: Eichhornia.

Explanation

Sucker is a short and weak lateral branch that grows diagonally upwards and directly gives rise to a new shoot. E.g: Chrysanthemum.

Explanation

Phylloclade: In dry climate, conserving water is a challenge. Water evaporates from the surface. If
the surface area is larger, evaporation would be more; and if the surface area is smaller, the evaporation will be less. Plants with many leaves have more surface area. Cactus hence has a thick stem which does most of the food production through photosynthesis and leaves are reduced to small spines with less surface area.

Explanation

Stolon is a slender branch of the stem that grows upwards to some distance and then bends towards the ground. Upon touching the ground, it gives rise to a new plant. E.g: Wild strawberry.

Explanation

In aerial and sub aerial modifications, stem has indefinite growth. In underground modified stem,
whole stem is buried under the ground and it has definite growth. Usually stem grows above the ground, but there are some stems that grow under the ground to store food. These underground stems swell and become thick. There are four types of underground stems: 1. Rhizome; 2. Corm; 3. Tuber; 4. Bulb.

Explanation

Tuber is an enlarged, spherical underground stem that stores food. It has many dormant buds on its surface known as “Eyes”. If we plant a part of tuber with the bud, it grows into a new plant.

Explanation

Potato is an example of Tuber.

Explanation

Rhizome is an underground thick stem with nodes and internodes with scale leaves at the node. It grows horizontally and has an irregular shape. Rhizome have buds. If give rise to new stem and leaves.

Explanation

Corm is an underground stem which is round in shape and flat at the top and bottom. It is a condensed form of rhizome and bears one or more buds in the axils of scale leaves. Daughter plants arise from their buds.

Explanation

Ginger and Turmeric are example of Rhizome.

Explanation

Colocasia is an example of corm.

Explanation

Bulb is a condensed stem which is disc like and stores food in the fleshy leaves.

Explanation

The bulb has two types of leaves. 1. Fleshy Leaves 2. Scaly Leaves. The upper part of the stem has a terminal bud and it is covered by many scaly leaves. The inner fleshy leaves store food as seen in Garlic and Onion.

Explanation

Plants have changed themselves to adapt to the environment they grow. One of them is the modification of leaves. Leaves of several plants get modified into different form based on the purpose and environment. They are i. Spines, ii. Tendrils, iii. Phyllode and iv. Traps.

Explanation

Nepenthes is the example of Traps.

Explanation

Plants that grow in nitrogen deficient places adapt themselves well to get it. In Nepenthes, the
leaves are modified into a flask like structure, which is used to attract insects and other tiny animals. The inner wall of the leaf secretes digestive enzymes that help to digest the insects and extract the nitrogen needed for the plant. Eg: Nepenthes.

Explanation

Leaves are reduced to spines, and the stem is modified into green succulent part to perform photosynthesis. Eg : Opuntia