Most Important Diagrams Class 11 Biology (Botany) - NEET 2023 Biology Exam Preparation

Diagrams play a pivotal role in NEET biology MCQs. Here, let us look at some important botany diagrams from class 11 NCERT. The chapters covered are – Plant Kingdom, Morphology of Flowering Plants, Mineral Nutrition, Transport in Plants, Anatomy of Flowering Plants and Photosynthesis in Higher Plants.

Table of Contents:

• Plant Kingdom
• Morphology of Flowering Plants
• Anatomy of Flowering Plants
• Transport in Plants
• Mineral Nutrition
• Photosynthesis in Higher Plants

Plant Kingdom

The chapter Plant Kingdom discusses various bryophytes, algae, gymnosperms, angiosperms and pteridophytes. The chapter also includes the life cycle diagram of plants. Any of the plant diagrams could be given to identify the parts. Likewise, life cycle diagrams could also be asked for NEET.

Brown Algae

Brown algae belong to the class Phaeophyceae. Fucoxanthin is the vital xanthophyll pigment in these plants that are responsible for the brown colour. Examples – Ectocarpus and Fucus. Brown algae can be easily identified by the following characteristic features –

• Ectocarpus has a more differentiated thallus. Generally, the thallus or body of algae lacks true stems, roots and leaves.
• They have a root-like structure that provides anchorage and takes part in transportation. It is called a holdfast. They also have a stem-like stalk called the stipe.
• They have a flattened blade-like structure called the frond or lamina that is similar to leaves. Here, the front is the photosynthetic structure.
• The Fucus has air bladders to provide buoyancy.

Red Algae

Red algae belong to the class Rhodophyceae. They are red in colour due to the presence of pigments like chlorophyll A, phycoerythrin and phycocyanin. Examples – Gellidium and Polysiphonia. Gellidium is a genus of thalloid red algae and Polysiphonia is a genus of filamentous red algae that has a bushy structure. A jelly-like substance called agar-agar is mainly obtained from Gellidium.

Green Algae

These algae are more cosmopolitan than the other algae. Green algae belong to the class Chlorophyceae. They are green in colour due to the dominance of pigments like chlorophyll a and b like the higher plants. The following are some examples of green algae.

• Chara is a branched form of edible green algae that can also be used as a manure.
• Chlamydomonas is a unicellular pyriform (pear-shaped) algae that is biflagellate. The two flagella are apical in position. Also, they have a cup-shaped chloroplast. This genus is a colonial form that shows isogamous, anisogamous, as well as oogamous modes of sexual reproduction.
• Spirogyra is a filamentous alga with a ribbon-like chloroplast. Ulothrix is also a filamentous alga but has a girdle-shaped chloroplast. Volvox is a globular green alga.

Modes of sexual reproduction – Sexual reproduction happens through the fusion of gametes. If both the gametes are similar in size, then it is isogamous. It can be non-flagellated as Spirogyra or flagellated as Ulothrix. If two gametes of dissimilar size fuse, then it is anisogamous. Example – Eudornia (green algae). The fusion between large non-motile female and small motile male is called oogamous. Example – Fucus and Volvox.

Alternation of Generations

Morphology of Flowering Plants

A wide range of diversified morphology or external structure of flowering plants is discussed in this chapter. Floral parts, floral formula and floral diagrams are the notable questions that can be asked from this chapter.

Aestivation

The arrangement of petals or sepals with respect to each other is called aestivation. It can be –

1. Valvate – Here, the petals or sepals in a whorl just touch each other without overlapping. Example – Calotropis.
2. Vexillary – The large petal or sepal overlaps the two lateral wings which in turn overlaps the two keel (smallest anterior petal); it is called vexillary aestivation. Example – Pea and bean flowers.
3. Twisted – If one margin overlaps the next one, then it is twisted. Example – China rose, lady’s finger and cotton.
4. Imbricate – If the margin overlaps but not in a particular direction then it is imbricate. Example – Cassia and Gulmohar.

Placentation

It is nothing but the arrangement of ovules within the ovary. Placentation can be any of the following –

1. Axile – Placenta is axile and the ovules are attached in a multilocular ovary. Examples – China rose, lemon and tomato.
2. Parietal – Ovules develop on the inner wall or periphery of the ovary. The ovary becomes two-chambered due to the formation of a false septum. Examples – Argemone and mustard.
3. Free central – Ovules are borne on the central axis and the septa are absent. Examples – Dianthus and Primrose.
4. Basal – Placenta develops at the base of the ovary and only a single ovule is attached to it. Examples – Sunflower and marigold.
5. Marginal Placentation – Here, the placenta forms a ridge along the ventral joint of the ovary. The ovules are borne on this ridge forming two rows. Example – Pea.

Anatomy of Flowering Plants

This chapter deals with the internal structures of plants and has some very important diagrams. It encompasses the diagram of permanent tissues and the anatomy of monocotyledonous and dicotyledonous roots, leaves and stems.

T. S. of Dicot Stem

• It shows the outermost protective epidermis with epidermal hair or trichomes. The dicot stem is covered with a thin cuticle which bears the trichomes and also has a few stomata.
• The cortex of the stem is divided into 3 – hypodermis (outer), general cortex or middle cortical layer and the inner endodermis.
• The hypodermis is rich in collenchyma and the cortical layer below it is rich in the parenchyma. The endodermis is rich in starch and is also known as the starch sheath.
• Pericycle is present on the inner side of the endodermis and is sclerenchymatous in nature.
• Then comes the vascular bundles, which are open, conjoint, and endarch structures. Endarch denotes the protoxylem in the centre and the metaxylem on the periphery.
• The innermost core part is the pith which is well-developed.

Transport in Plants

The absorption of water in roots happens in two pathways – apoplastic and symplastic. The system of cell walls that is continuous throughout the plant, except at the Casparian strips, is called apoplast. It is the space outside the cell membrane. Casparian strips are seen in the endodermis of the dicot root and are impervious to water. Apoplastic movement of water includes the movement through walls of the cells and intercellular spaces. This water movement is gradient dependent. It has nothing to do with cytoplasm or cell membrane. In the apoplastic pathway, water cannot pass through the endodermis due to the presence of suberin. Thus movement beyond the cortex is blocked. Now the symplastic pathway comes into action. It involves the protoplasm of cells. The water passes through intercellular connections called the plasmodesmata. Here, the movement of water is relatively slower.

The water moving through the symplast should pass through a membrane to reach the cells of the xylem.

Mineral Nutrition

This chapter chiefly focuses on inorganic plant nutrition. Most importantly, It also deals with the mechanism of nitrogen fixation.

Nodule Formation

This process deals with sequential interactions between the roots of the host plant and the Rhizobium bacteria. The NCERT diagram explains the development of root nodules in soybean.

• First, the Rhizobium bacteria contact the susceptible root hair and divide near it.
• After successfully infecting the root hair, it causes it to curl (hook formation). Now, the bacteria multiply rapidly and the infected thread carries them to the inner cortex.
• Here, they become rod-shaped bacteroids and cause inner pericycle and cortical cells to divide. This division leads to nodule formation.

A mature nodule is complete with vascular tissues and is continuous with those roots. They are commonly found in leguminous plants.

Photosynthesis in Higher Plants

This chapter includes a variety of graphs denoting different pigments and their absorption spectrum. Generally, the leaf colour that we see is due to different pigments like – chlorophyll a (blue green), xanthophylls (yellow), chlorophyll b (yellow green) and carotenoids (yellow orange). These pigments have the ability to absorb light at different wavelengths.

Absorption spectrum – It is the curve that shows the absorption of energy at different wavelengths of light in VIBGYOR.

In the below diagram, a denotes chlorophyll a , b is chlorophyll b and c is carotenoids. The absorption of chlorophyll b is maximum in the blue-violet region. Likewise, the absorption of chlorophyll a has peak in the red region. Chlorophyll a is called primary pigment as it shows a higher absorption in both the blue-violet and red range. All the remaining pigments are called accessory pigments.

Then comes the action spectrum graph which shows the relative rate of photosynthesis at different wavelengths. There is also a separate graph in NCERT that deals with the action spectrum of photosynthesis that is superimposed on the absorption spectrum of chlorophyll A.

Z-Scheme

Z-scheme is the light driven photophosphorylation which is also known as non-cyclic or Hill reaction. The Z-scheme starts from the PS Ⅱ. The electrons are removed and donated to the non-excited oxidised form of P680. Here, the electrons jump and the electron carriers are waiting for it. This jumping and carrying of electrons happen along the redox potential. The loss of electrons by P680 (PS Ⅱ) is occupied by the P700 (PS Ⅰ). Now the PS Ⅰ gets excited and releases electrons which finally get accepted by the NADP⁺ and become NADPH + H⁺. This results in the production of ATP molecules.

This reaction involves many uphill and downhill processes which give the characteristic Z representation. Here, both photosystems (PS Ⅰ and PS Ⅱ) work in coordination.

Also Check: MCQs on Electron Transport System

Recommended Video

Check BYJU’S NEET for more such interesting and important diagram concepts related to the NEET exam.

Related Topics: