Morphology of Flowering Plants
- Stem is ascending cylindrical axis of plant body which develops from the plumule of embryo and grows by means of terminal bud
- Stem branches are exogenous in origin.
- Bud is a condensed, undeveloped, compact, embryonic shoot having a growing point covered with a gowded overlapping in mature leaves.
- According to nature bud are classified into vegetative, floral and mixed buds.
- On the basis of position buds are of 2 types (i) Terminal buds and (ii) lateral buds. [both axillary, accessory buds]
- Active and dormant are the two types of buds on the activity.
- Buds are modified into following ways
(i) Bulbils Eg : Agave, onion
(ii) Apical bud : Eg : Cabbage
(iii) Turions : Hydrophytes
(iv) Tendrils : Cucurbita, passiflora
(v) Thorns : Duranta
- Unbranched stem is called caudex (Eg : palm)
- Culm is that caudex in which nodes and inter nodes are well district Eg : Bamboo
- Branching is of 2 types : (i) Dichotonomous (Eg : liverworts, Dictyota) and (ii) lateral (Eg : Eucalyptus, Polyalthia, mustard, viscus, Croton).
- Stem is of 3 forms : (i) Aerial (ii) Sub aerial and (iii) Underground
- Aerial / Epiterranean stem is above the ground which is of 3 types (1) Reduced (2) Erect and (3) Weak
- Reduced : Eg : Radish, Carrot, Turnip, Lemna, Wolfia.
- Twiners (Eg : Convolvulus, Ipomoea, Bean, Asparagus) and climbers are the 2 types of weak type.
- The weak stem plants rise up with the help of some clinging (or) coiling structures which has 3 different types.
(i) Tendril climbers (eg : root and stem climbers)
- The weak stems take the support of ground for spreading which is of 4 types.
- (Eg : Tribulus, evolvulus) (Eg : Tridase, Portulaca)
- Runners : Eg : Oxalis, lawn grass, centella
- Stolons : They may be above the ground (Eg : Strawberry) (or) Underground (Eg : Colocosia)
- Offsets are one internode long thicke, short runners formed in rosette plants at ground or water level. Eg : Water lettuce (Pistia) and Eichornia
- Sucker (Eg : Chrysanthemum, mint) [Banana possess sword suckers]; Rhizome (eg : ginger, Turmeric, canna, Banana, Avoids); Corm (Eg : Amorphophallus, Colocossia, Fresia, Colchicum and Gladiolus); Bulb (Simple tunicated bulb - onion ; compound Tunicated bulb - Garlic : Scaly bulb ; lily): (Tubers, potato, Helianthus, Stachys)
- Each tuber has a number of eyes (nodes) and 3 buds and therefore eye represents node and axillary buds. Eyes are more towards distal and where terminal bud is present and then end is called rose end.
- The skin has corky covering with tentacles : Eye represent seed of a plant.
- Aerial stem modification by providing support and protection.
- Stem tendrils (Eg : Passiflora, Cucurbita, Antigonon)
- Stem thorns (Eg : Citrus, Pomegranate, Bougainvillea)
- Phylloclades are green, photosynthetic, often succulent stems of indefinite growth which is an adaptation to dry habitats (Eg : Euphorbia, opuntia, casuarina)
- Cladodes (Cladophylls) are green stems of limited growth. (Eg : Ruscus, Asparagus, Lemna)
View this video for the topic from 16:36 to 26:04
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