CBSE Biology Experiment Features of Monocots and Dicots

Biology Experiment - Features of Monocots and Dicots

Have you looked at a blade of grass closely? Its leaves are distinctly different from those of a rose plant, or a mango plant, aren’t they? If you dig up to see the root systems, they’ll appear different too.

• Grasses and well-developed plants such as the rose or mustard are all flowering plants whose seeds are enclosed within fruits. 

• However, the external morphologies and internal anatomies of their stems, leaves, flowers, and roots are different, based on the number of cotyledons present in their seeds. 

• Let’s perform this simple experiment to understand the differences between monocots and dicots.

Table of Content

• Aim

• Apparatus Required

• Theory

• Procedure

• Observations

• Result

• Precautions

• Lab Manual Questions

• Viva Questions

• Practical Based Questions

Aim

To study the features of the stem, leaves, flowers, roots, and seeds of monocots and dicots and understand the differences between the two groups of plants.

Apparatus Required

An intact monocot plant (maize, onion, paddy, etc.), intact dicot plant (mustard, pea, rose, hibiscus, etc.), simple microscope, hand lens, glass slide, cover slip, a razor blade, water, Petri dish, and pre-soaked seeds of gram and maize. 

Theory

• The angiosperms are distinctly known for their characteristic flowers and seeds enclosed within fruits. 

• They are further divided into two groups - plants with seeds that bear a single cotyledon (namely, the monocots) and those plants that bear two cotyledons in their seeds (the dicots).

Features of Monocots

• The embryo within the seed contains only one cotyledon. 

• Stems are non-woody and weak. Vascular bundles are scattered. 

• Parallel venation present in leaves.

• The root system is fibrous type.

• The flowers are trimerous - The different floral parts including the sepals, petals, stamens, and carpels are present in multiples of three.

• Examples of monocots include maize, wheat, rice, bamboo, etc. 

Features of Dicots

• Seeds with two cotyledons within their embryos. 

• Strong, woody stems. Vascular bundles are arranged in the form of a ring. 

• Reticulate venation present in leaves. 

• The root system is characteristic of taproot type. 

• The flowers are pentamerous.   

• Examples of dicots include peas, beans, mango, magnolia, rose, tomatoes, etc.

Procedure

1. Carefully separate the leaves, roots, and flowers of both plants.

2. Observe the roots of each of the plants. Note down your observations. 

3. Now, move on to the leaves. Observe their shape. 

4. Using a hand lens, observe the pattern of venation in the leaves of both plants. 

5. For the flower, count the number of petals, sepals, and stamens in each plant. 

6. Now observe the stems of both plants.

7. Cut an even, thin transverse section of the stem using a razor blade. Be careful!

8. Now, take a glass slide and add just one drop of water to its centre. Carefully transfer the stem T.S. onto a glass slide. Cover the slide with its cover slip.

9. Observe the T.S. of the stem under the microscope. 

10. Remove the seed coat of each of the two seeds and open them up. Record the number of cotyledons present in them. 

Observations

Differences between dicots and monocots

Result

From this experiment, it is revealed that the monocots have tuft-like roots, leaves with parallel venation, scattered vascular bundles, and tetramerous flowers. Contrarily, the dicots have taproots, leaves with reticulate venation, vascular bundles arranged in a ring, and pentamerous (or tetramerous) flowers. 

Precautions 

1. Handle the specimens with care, ensuring that there’s no breakage or loss of any parts. 

2. Care must be taken while handling the razor blade.

3. The T.S. must be very thin and evenly cut.

4. Do not keep the T.S. out in the open for long, as the section may dry.

5. The coverslip must be placed gently with the help of a needle, to avoid air bubbles.

Lab Manual Questions

1. What are the features of a typical dicot seed?

Ans: A typical dicotyledonous seed has a seed coat, a hilum, a micropylar pore, two cotyledons, the endosperm and radicle, and a plumule.

2. What are the differentiating features of the vascular bundles of maize and gram?

Ans: Maize is a monocot, hence its vascular bundles will appear scattered under a microscope. Contrastingly, the vascular bundles of the gram appear arranged as a ring, owing to its dicot nature.

3. Pentamerous flowers are a feature of which group of plants?

Ans: Pentamerous flowers are seen in dicots. 

Viva Questions 

1. Do the plants selected for this experiment have anything in common?

Ans: Yes. Both the plants belong to the sub-kingdom angiosperms of kingdom Plantae; hence, they bear flowers and their seeds are covered with fruits.

2. If a plant has been randomly given to you, how will you determine the number of cotyledons that its seeds bear?

Ans: I will look at the leaves of the plant. If the leaves have parallel venation, it is a monocot. If reticulate venation is observed, the plant is a dicot. 

3. A monocotyledonous seed has a single cotyledon. What are the other distinguishing parts of a monocot seed?

Ans: Apart from the cotyledon, a monocot seed possesses a seed coat, the endosperm, an aleurone layer, the embryo, a scutellum, and the coleoptile and the coleorhiza.

4. What are some other examples of monocots?

Ans: Maize, wheat, onion, orchids, ginger, bamboo, etc.

5. How many whorls do a typical flower have? What are they? 

Ans: A flower typically has 4 whorls - the sepals, petals, the androecium, and the gynoecium. 

6. What do you understand by the term incomplete flowers? 

Ans: An incomplete flower lacks one or more whorls typical of a flower. 

7. What are the radicle and the plumule?

Ans: The radicle is that part of the embryo of the seed, which eventually develops into the root system of the plant. It is the first structure of a plant that arises in the plant embryo. The plumule is the initial shoot of the embryo that forms above the epicotyl of the embryonic axis.

8. What do you understand by the term carpel?

Ans: The carpel is the female reproductive organ of the plant. A flower may contain one or more carpels. Each carpel comprises an ovary, a stigma, and a style. 

Practical Based Questions 

1. You’ve been given a plant that has reticulate venation in its leaves. Which of the following options is the plant most likely to be?

1. Maize

2. Bamboo

3. Corn

4. Mustard 

Ans: D) Mustard

2. Which of the following is not a characteristic of monocot plants?

1. Parallel venation

2. Scattered vascular bundles

3. Tetramerous flowers 

4. Scutellum in seed

Ans: C) Tetramerous flowers

3. In monocot stems, a greater number of vascular bundles are seen near the

1. Centre 

2. Pith 

3. Periphery 

4. Stele

Ans: C) Periphery

4. Which of the following is an exclusive characteristic of a dicot seed?

1. Scutellum

2. Cotyledons 

3. Seed coat

4. Hilum 

Ans: D) Hilum

5. Floral whorls in a dicot are present in multiples of: 

1. 3

2. 4

3. 5

4. Both b and c

Ans: D) Both b and c

6. Which of the following groups comprises only dicot plants?

1. Maize, wheat, corn, mango

2. Mango, palm, mustard, apple 

3. Corn, maize, castor, mustard

4. Mustard, gram, pea, hibiscus

Ans: D) Mustard, gram, pea, hibiscus

7. A particular plant is found to have 24 petals and leaves that have parallel venation. The root system that is most likely to be found in this plant is:

1. Tap root

2. Adventitious root

3. Fibrous root 

4. Stilt roots 

Ans: C) Fibrous roots 

8. In the T.S. of the stem of a hibiscus, the most likely observation is 

1. Scattered vascular bundles

2. A greater amount of vascular bundles at the periphery

3. A greater amount of vascular bundles at the centre 

4. Vascular bundles in a circular arrangement 

Ans: D) Vascular bundles in a circular arrangement 

Conclusions 

From the observations made, we can conclude that since specimen A has a fibrous root system, parallel venation, tetramerous flowers, and a single cotyledon in its seed, it  is a monocot. On the other hand, specimen B is conclusively a dicot, since it has  a tap root system, reticulate venation, pentamerous flowers, and two cotyledons in its seeds.