Aerial modification of stem :
1. Creepers: These are plants growing closer (horizontally) to the ground and produces roots at each node. e.g., Cynodon dactylon, Oxalis, Centella
2. Trailers (Stragglers): It is a weak stem that spreads over the surface of the ground without rooting at nodes. They are divided into 3 types,
i. Prostrate (Procumbent) : A stem that grows flat on the ground. e.g., Evolvulus alsinoides, Indigofera prostrata.
ii. Decumbent : A stem that grows flat but becomes erect during reproductive stage. e.g., Portulaca, Tridax, Lindenbergia
iii. Diffuse : A trailing stem with spreading branches. e.g., Boerhaavia diffusa, Merremia tridentate
3. Climbers: These plants have long weak stem and produce special organs for attachment for climbing over a support. Climbing helps to display the leaves towards sunlight and to position the flower for effective pollination.
i. Root climbers: Plants climbing with the help of adventitious roots (arise from nodes) as in species of Piper betel, Piper nigrum, Hedera helix, Pothos, Hoya.
ii. Stem climbers (twiners) : These climbers lack specialised structure for climbing and the stem itself coils around the support. e.g., Ipomoea, Convolvulus, Dolichos, Clitoria, Quisqualis.
Stem climbers may coil around the support clockwise or anti-clockwise. Clockwise coiling climbers are called dextrose. Example: Dioscorea alata. Anti-clockwise coiling climbers are called sinistrose. e.g., Dioscorea bulbifera.
iii. Hook climbers: These plants produce specialized hook like structures which are the modification of various organs of the plant. In Artabotrys inflorescence axis is modified into hook. In calamus (curved hook) leaf tip is modified into hook. In Bignonia unguiscati the leaflets are modified into curved hook. In Hugonia the axillary buds modis into hook.
Iv. Thorn climbers : Climbing or reclining on the support with the help of thorns as in Bougainvillea and Carissa.
v. Lianas (woody stem climber): Woody perennial climbers found in tropical forests lianas. They twine themselves around tall trees to get light. e.g., Hiptage benghalensis, Bauhinia vahlii, Entada pursaetha.
vi. Tendril climbers: Tendrils are thread-like coiling structures which help the plants in climbing. Tendrils may be modifications of Stem - as in Passiflora, Vitis and Cissus quodrangularis, Inflorescence axis - Antigonon, Leaf - Lathyrus, Leaflets - Pisum sativum, Petiole - Clematis, Leaftip - Gloriosa, Stipules - Smilax. In pitcher plant (Nepenthes) the midrib of the leaf often coils around a support like a tendril and holds the pitcher in a vertical position.
