Essay on the Lamina of a Leaf: Top 6 Essays | Angiosperms | Botany

Here is an essay on the ‘Lamina of a Leaf’ for class 9, 10, 11 and 12. Find paragraphs, long and short essays on the ‘Lamina of a Leaf’ especially written for school and college students.

Essay # 1. Shape of Lamina:

The lamina shows much variation with regard to their shapes.

These are divided into three main groups:

a. Lamina with almost same width throughout.

1. Acicular:

Lamina is needle-shaped, long, thin and pointed, e.g., Pinus sp. (Fig. 2.62A).

2. Linear:

Lamina is long and very narrow with nearly parallel margins, e.g., tube-rose, Polyanthes tuberosa, rice, wheat and in many grasses (Fig. 2.62B).

b. Lamina with widest middle.

3. Lanceolate:

Lamina is broadest in the middle or a little below and tapering towards both the ends, e.g., oleander, Nerium indicum (Fig. 2.62C) of Apocynaceae, Polygonum orientate of Polygonaceae, Butomopsis lanceolata of Alismataceae etc.

4. Oblong:

Lamina is almost rectangular i.e., flat and broad with a round apex, e.g., banana, Musa paradisiaca of Musaceae (Fig. 2.62D) etc.

c. Lamina with widest base.

5. Subulate or Awl-Shaped:

Lamina is long and narrow, tapering gradually from base to apex, e.g., saltwort, Salsola kali of Chenopodiaceae; Isoetes (Fig. 2.62E), a pteridophyte.

6. Ovate or Egg-Shaped:

Base of lamina is wider than the apex, e.g., banyan, Ficus benghalensis of Moraceae; Solanum nigrum of Solanaceae; china-rose, Hibiscus rosa-sinensis (Fig. 2.62F) etc.

7. Cordate:

Lamina is heart-shaped, i.e., its base is broad and lobed and has a pointed apex, e.g., betel vine, Piper betel (Fig. 2.62G) of Piperaceae; Sida cordifolia and Abutilon indicum of Malvaceae etc.

8. Sagittate:

Lamina is arrow-shaped i.e., two lower lobes, one on each side pointing downwards, e.g., Sagittaria sagittifolia (Fig. 2.62H) of Alismataceae; Ipomoea aquatica of Convolvulaceae etc.

9. Hastate:

Lamina is arrow-shaped, but the two lower lobes are directed out­wards, e.g., Ipomoea sp. (Fig. 2.62I) of Convolvulaceae; Typhonium trilobatum of Araceae.

10. Reniform or Kidney-Shaped:

Lamina is rounded above with a deep notch at its base, e.g., Indian pennywort, Centella asiatica (Fig. 2.62J) of Apiaceae.

11. Lunate:

Lamina is like a half-moon with pointed basal lobes i.e., semicircular in outline, e.g., Adiantum lunatum, a pteridophyte; Passiflora lunata (Fig. 2.62K) of Passifloraceae etc.

d. Lamina with widest apex.

12. Obovate:

Lamina is like an inverted egg (reverse of ovate), e.g., jack, Artocarpus heterophyllus (Fig. 2.62L) of Moraceae; Cassia obovata of Fabaceae etc.

13. Obcordate:

Lamina is like an inverted heart i.e., its apical region is broad and bilobed, e.g., Bauhinia variegata (Fig. 2.62M) of Fabaceae; Oxalis corniculata of Oxalidaceae etc.

14. Spathulate or Spathula-Shaped:

Lamina is broad and rounded at the apex and gradually tapers towards the base, e.g., Phyla nodiflora (Fig. 2.62N) and Duranta repens of Verbenaceae; Drosera burmanii of Droseraceae etc.

15. Cuneate or Wedge-Shaped:

Lamina looks like the hood of a snake i.e., its breadth increases towards the apex, e.g., water lettuce, Pistia stratiotes (Fig. 2.62O) of Araceae.

16. Lyrate or Lyre-Shaped:

Lamina looks like a lyre having a large oval terminal lobe and two or more smaller lobes, e.g., radish, Raphanus sativus and mustard, Brassica nigra (Fig. 2.62P) of Brassica­ceae.

e. Lamina symmetrical.

17. Elliptical or Oval:

Lamina is like an ellipse, e.g., Indian rubber, Ficus elastica of Moraceae; guava, Psidium guajava of Myrtaceae (Fig. 2.62Q) etc.

18. Orbicular (Circular) or Rotund or Peltiform:

Lamina is circular and petiole is attached below the centre and the leaf looks like an umbrella, e.g., lotus, Nelumbo nucifera (Fig. 2.62R) of Nymphaeaceae etc.

Essay # 2. Base of Lamina:

The base of lamina is of different types:

1. Auriculate:

Leaf-bases of the sessile leaves form two lobes like that of wings, which par­tially surround the stem, e.g., Mexican poppy, Argemone mexicana of Papaveraceae, Calotropis procera (Fig. 2.63A) of Asclepiadaceae etc.

2. Perfoliate:

Lobes of sessile leaf become fused together; thereby the leaf completely surrounds the stem, e.g., Canscora perfoliata (Fig. 2.63B) of Gentianaceae, Aloe perfolia­ta of Liliaceae etc.

3. Connate:

Bases of two sessile leaves with opposite phyllotaxy are completely fused together, e.g., Canscora diffusa (Fig. 2.63C) and Swertia chirata of Gentianaceae etc.

4. Decurrent:

Leaf base is winged and fused with the stem, e.g., Laggera alata and Sphaeranthus indicus (Fig. 2.63D) of Asteraceae.

Essay # 3. Surface of Lamina:

The surface of lamina is of different types:

1. Glabrous:

Surface of lamina is smooth and free from hairs, e.g., Pongamia glabra of Fabaceae; pink, Dianthus chinensis of Caryophyllaceae.

2. Glaucus:

Surface of lamina has a coating of wax and appears to be shiny, e.g., Solanum glaucum of Solanaceae.

3. Viscose:

Surface of lamina becomes sticky due to some sugary exudation, e.g., Cleome viscosa and Polanisia icosandra of Capparidaceae.

4. Scabrous:

Surface of lamina is rough due to some short rigid points, e.g., Ficus hispida of Moraceae.

5. Rugose:

Surface of lamina is somewhat wrinkled, e.g., Rubus rugosus of Rosaceae.

6. Gland-Dotted:

Surface of lamina becomes covered with glands, e.g., lemon, C. aurantifolia of Rutaceae.

7. Hairy:

Surface of lamina becomes covered with hairs.

These are of the following types:

a. Pilose:

Covered with long, soft and scat­tered hairs, e.g., Grewia flavescens of Tiliaceae.

b. Hispid:

Covered with long, rigid scat­tered hairs, e.g., Cucurbits.

c. Hirsute:

Covered with stiff, fine and scattered hairs, e.g., Eclipta alba of Asteraceae.

d. Tomentose:

Covered with short, dense and cottony hairs, e.g., Calotropis procera of Asclepiadaceae, Guazuma tomentosa of Sterculiaceae etc.

e. Woolly:

Covered with long and inter­woven hairs like wool, e.g., Solarium verbescifolium of Solanaceae.

8. Spinose:

Surface of lamina is overed with pri­ckles. e.g., Hibiscus esculentus of Malvaceae.

Essay # 4. Margin of Lamina:

The margin of the lamina may be of the following types:

1. Entire:

Margin is smooth i.e., without inden­tations (Fig. 2.64A), e.g., mango, Mangifera indica; banyan, Ficus benghalensis.

2. Repand:

Margin is wavy with indentations < 1/16 distance to midrib (Fig. 2.64B), e.g., Polyalthia longifolia of Annonaceae.

3. Serrate:

Margin is like the teeth of a saw, pointed upwards (Fig. 2.64C), e.g., china- rose, Hibiscus rosa-sinensis.

4. Biserrate:

Margin is toothed but the teeth again become serrated (Fig. 2.64D), e.g., elm tree.

5. Retroserrate:

Margin is toothed and pointed downwards (Fig. 2.64E).

6. Dentate:

Margin is toothed and the teeth are pointed outward at right angles to midrib (Fig. 2.64F), e.g., water-lily.

7. Bidentate:

Margin is toothed and the teeth are again dentate (Fig. 2.64G).

8. Crenate:

Margin is toothed and the teeth are rounded (Fig. 2.64H), e.g., Centella asiatica of Apiaceae.

9. Bicrenate:

Margin is toothed and the teeth are crenate (Fig. 2.64I).

10. Spiny:

Margin is toothed and the teeth are pointed to form spines (Fig. 2.64J), e.g., Mexi­can poppy, Argemone mexicana of Papaveraceae; Solanum xanthocarpum of Solanaceae.

11. Incised or Lobed:

Margin is incised into various depths and divided into small lobes (Fig. 2.64K), e.g., mustard, Brassica nigra; radish, Raphanus sativa etc.

Essay # 5. Apex of Lamina:

The apex of lamina is of the following types:

1. Acute:

Apex is pointed forming a terminal angle of 45°-90°, e.g., mango, Mangifera indicia (Fig. 2.65A); china-rose, Hibiscus rosa-sinensis etc.

2. Acuminate:

Apex is slender and much pro­longed like a tapering tail forming a terminal angle of < 45°, e.g., peepul tree, Ficus religiosa (Fig. 2.65B) of Moraceae, Bauhinia acuminata of Fabaceae (Caesalpiniaceae).

3. Obtuse:

Apex is broad angled (>90°) and blunt, e.g., banyan, Ficus benghalensis (Fig. 2.65C).

4. Mucronate:

Apex is as broad as or broader than long and forms a sharp point, e.g., Catharanthus roseus (Fig. 2.65D) of Apocynaceae.

5. Cuspidate or Spiny:

Apex ends in a hard and pointed structure, e.g., date palm, Phoenix sylvestris (Fig. 2.65E) of Arecaceae, Agave cantula of Agavaceae etc.

6. Tendrillar:

Apex becomes narrowed and forms a tendril, e.g., glory lily, Gloriosa superba (Fig. 2.65F) of Liliaceae.

7. Cirrhose:

Apex ends in a fine thread-like coiled or flexuous structure, e.g., banana, Musa paradisiaca (Fig. 2.65G) of Musaceae.

8. Truncate:

Apex is cut across abruptly, almost at right angle to midrib, e.g., Indigofera linifolia of Fabaceae, Paris polyphylla (Fig. 2.65H) of Liliaceae etc.

9. Retuse:

Obtuse apex is slightly notched, e.g., Clitorea ternatea of Fabaceae, water lettuce, Pistia stratiotes (Fig. 2.65I) of Araceae etc.

10. Emarginate:

Obtuse apex is deeply notched, e.g., Bauhinia variegata (Fig. 2.65J) of Fabaceae.

Essay # 6. Texture of Lamina:

1. Coriaceous:

Lamina is thick and leathery, e.g., mango, Mangifera indica; Indian rub­ber, Ficus elastica; Vanda roxburghii and Vanilla planifolia of Orchidaceae.

2. Herbaceous:

Lamina is thin and mem­branous, e.g., china-rose, Hibiscus rosasinensis; rose, Rosa centifolia etc.

3. Succulent:

Lamina is fleshy and more or less brittle, e.g., Aloe indica of Liliaceae, Bryophyllum calycinum of Crassulaceae.

4. Gland-Dotted or Glandular:

Lamina is dotted with glands and the glands are filled with essential oil, e.g., lemon, Citrus limon of Rutaceae; custard apple, Annona squamosa of Annonaceae.