Morphology of Flowering Plants Test - 5

Phyllode is flattened petiole or rschis of a leaf  which carries out the function of photosynthesis (e.g., Parkinsonia, Acacia). In  these plants lamina is either absent or  reduced, to reduce the transpiring area. In  Asparagus, dadode type of stem modification  can be seen. Cladodes are slightly flattened,  fleshy, straight or curved pointed structures  which develop in dusters in the axils of scale  leaves.

Leaf tendrils are thread-like sensitive  structures which can coil around a support to  help the plant in climbing. Leaf tendrils are  usually unbranched and devoid of scales, e.g.,  leaflet tendrils in Pisum sativum (peas), and  leaf tip tendrils in Gloriosa (Glory lily).

In many legumes leaf base is swollen, it is known as pulvinus. It is responsible for sleep and shock movements of certain leaves, e.g., Mimosa pudica.

In opposite phyllotaxy two leaves are borne on the opposite side of a single node. Opposite phyllotaxy is of two types: (i) Opposite and superposed e.g., Syzygium, (ii) Opposite and decussate, e.g., Calotropis, Zinnia.

In case of parallel venation the veins run parallel to each other and network is not formed. This type of venation is the characteristic features of monocots. There are few exceptions, e.g, Smilax, Colocasia, Alocasia, Dioscorea, etc.

In Nepenthes (pitcher plant), the leaves are modified into pitchers to catch and digest the insects. The pitcher of Nepenthesls modified lamina. The apex of leaf is modified into lid which covers the opening of pitcher.

There are various parts of leaf that modifies into tendrils in plants. In plants, either entire leaf, upper leaflets, terminal bud, petiole or stipule gets modified into tendril. In Lathyrus aphasia, the entire leaf is modified into tendril. In Pisum sativum, the upper leaflets modified into tendrils. In Passiflora, the terminal bud is modified into tendrils. In Gloriosa, the leaf tip modified into tendril. In Clematis, the petiole is modified into tendril. In Smilax, the stipule is modified into tendril.

The petiole, rachis and the stalk of the leaflets (petiolules) in Clematis are sensitive to contact and can coil around the support to help the plant in climbing. Such tendrils are known as rachis and petiolule tendrils.

In reticulate venation, the veinlets form a reticulum or network. Reticulate venation is found in dicots (exceptions; Calophyllum, Corymbium, Eryngium, etc).

The submerged leaves of hydrophytes are often highly disserted or divided to create a very large surface area for absorption and photosynthesis. It also minimises water resistance and hence potential damage to the leaves due to tearing effect of water.

P - Banana, Canna
Q - Fan palm
R - Mango, Peepal
S - Smilax, Zizyphus

In alternate (or spiral) phyllotaxy, only one leaf is borne on a node and the leaves of the adjacent nodes roughly lie towards the opposite sides (e.g., Hibiscus). In opposite phyllotaxy, two leaves are borne on the opposite sides of a single node, e.g., guava in whorled or verticillate phyllotaxy, three (e.g., Nerium) or more than three (e.g., Alstonia) leaves develop from a single node.

In Dahlia, adventitious roots are modified to fasciculated fleshy roots which store food. Swollen roots or root tubers occur in clusters and lie at the base of stem.

Leaf bladders occur in the aquatic carnivorous plants of Utricularia (Bladderwort). Some of the leaf segments are modified to form small bladders. A bladder has sensitive hair, branched trigger bristles, a trap valve, internal and external glands for trapping and digesting small animals (e.g., water fleas). 

Phyllodes are flat, green coloured leaf like modification of petioles or tachis. The leaflets or lamia of the leaf are highly reduced or caducours.The phullodes perform photosynthesis and other functions of leaf. In Parkinsonia the leaves are bipinnately compound. The primary reaction each leaf isshort and modified intospine. The secondary rachis is modified into phyllodes.