EXPERIMENT 7.3 Objective. To identify and comment upon the specimens of leaf modifications.

                                                

EXPERIMENT 7.3

Objective. To identify and comment upon the specimens of leaf modifications.

REQUIREMENTS- Fresh or preserved specimens of modified leaves, practical note book, pencil, eraser etc.

PROCEDURE

1.Observe the specimen carefully and note down its special features.

2.Draw the specimen on the practical note book. Depict only the parts actually visible in the specimen.

3.Write down the morphological features and the features of special interest of the specimen.

OBSERVATIONS AND COMMENTS

1. WILD PEA (Lathyrus aphaca)

Identification. Whole leaf tendrils of Wild pea (Lathyrus odoratus).

Comments

(i) The leaves are completely modified into thin thread like structures called tendrils to help the plant in climbing.

(ii) The stipules become foliaceous to perform the function of photosynthesis.

(iii) An axillary bud is found in the axil of the tendril.

2. PEA (Pisum sativum)/SWEET PEA (Lathyrus odoratus)

Identification. Leaflet tendrils of Pea (Pisum sativum)/Sweet Pea (Lathyrus odoratus).

Comments

(i) A few upper leaflets of the pinnate compound leaves are modified into tendrils to help the plant in climbing.

(ii) The stipules become foliaceous to perform photosynthesis.

3. GARDEN NASTURTIUM (Tropaeolum majus)

Identification. Petiolar tendrils of Garden nasturtium (Tropaeolum majus).

Comments

(i) The petioles are elongated, sensitive and capable of coiling around the support and thus, act as tendrils.

(ii) The lamina of the leaves are normal.

4. CLEMATIS

Identification. Rachis and Petiolule Tendrils of Clematis.

Comments

(i) The petiole, rachis and petiolules (stalks of the leaflets) are sensitive to contact and can coil around the support to help the plant in climbing.

(ii) The leaflets are normal.

5. GLORY LILY (Gloriosa)

Identification. Leaf tip tendrils of Glory lily (Gloriosa).

Comments

(i) The apices of leaves are greatly elongated to function as tendrils to help the plant in climbing.

(ii) The lamina of the leaves are normal.

6. SMILAX

Identification. Stipular tendrils of Smilax.

Comments

(i) The stipules become thin, thread like and sensitive to coil around the support to help the plant in climbing.

(ii) The lower parts of the stipules are adnate with the petiole.

(iii) The lamina of the leaf is normal.

7. BARBERRY/CACTUS

Identification. Leaf spines of Barberry/Cactus.

Comments

(i) The leaves are changed into spines to protect the plant from grazing animals and excessive transpiration.

(ii) In Barberry, the leaves of the main stem are modified into branched 3-5 rayed spines. Dwarf or condensed branches arise in their axils. In Cactus/Opuntia, leaf spines in clusters arise on the aerolae.

8. PITCHER PLANT (Nepenthes)

Fig. 7.23. Leaf spines. A. Barberry. B. Cactus.

Identification. Leaf pitchers of Pitcher plant (Nepenthes).

Comments

(i) Nepenthes is an insectivorous plant, which supplement its nutrition by digestive insects.

(ii) The lamina of the leaf is modified into a large pitcher.

(iii) The leaf base is foliaceous while the leaf stalk is tendrillar.

(iv) The pitchers are meant for catching and digesting insects.

(v) The leaf apex gives rise to a coloured lid for attracting the insects.

(vi) The rim of the pitcher has nectariferous gland, that also help in attracting the insects.

9. BLADDER WORT (Utricularia)

pica Fig. 7.24. Leaf pitchers of Nepenthes (Pitcher plant).

A. A Rosette of leaf pitchers. B. Single leaf pitcher.

Identification. Leaf bladders of Bladder-wort (Utricularia).

Comments

(i) Utricularia is an aquatic plant having finely dissected leaves.

(ii) Some of the leaf segment are modified to form small bladders.

(iii)A bladder has sensitive hair, branched trigger bristles, a trap valve for trapping small animals such as water fleas.

10. AUSTRALIAN ACACIA (Acacia molanoxylon)

Identification. Phyllodes of Australian Acacia (Acacia molanoxylon).

Comments

(i)Australian acacia is a xerophytic plant.

(ii) The bipinnate lamina is absent and the petiole and part of the rachis become flattened into sickle shaped structures to perform photosynthesis.

(iii) Formation of phyllode is a mechanism to reduce transpiration.

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