The propagation of plant through the vegetative parts like leaf, stem & root artificially is called artificial vegetative propagation. This method is very useful for agricultural crops under vegetables, fruits & ornamental plants grown for decoration & beautification. There exists no variation and the propagate are true to their type to mother plant in artificial or natural method of vegetative propagation as it exists crossing over in sexual reproduction. Some techniques of vegetative propagation are cutting, layering, grafting, micropropagation etc.
This is simple but very useful method of vegetative propagation. Under this technique, plants are propagated by cutting of stem or roots. For this, branch or stem cutting of 8-30 cm long with high number of node and lateral buds is taken & proximal end of cutting is dipped in rootex hormone or auxin like Indole acetic acid (IAA) and planted slanting at 60 degree Celsius in nutrient rich moist soil. It will develop roots later and branches from lateral buds & finally new plant is developed. This technique is useful in horticultural crops like vegetables, fruits & ornamental plants like Dhupi, Rose, Bougainvillea, cacti etc. Some plants can develop roots when branches come in contact with soil that can be detached from mother plant for propagation.
It is process of developing root in branches of mother plant before detaching from it to plant as independent plant. In this technique adventitious roots are developed in branch which come in contact with soil & then only they are detached as cutting and planted as new plant. It is of two types:
In this method, the branch of stem which are situated at the lower part of stem are dragged into moist soil with node & keeping the tip part above the ground. For stabilizing the dragged branch, Y shaped peg/stake is used. Apply rooting hormone in that moist soil spraying water to keep it moist. After few days, adventitious roots are developed in the buried part of branch which is then detached from mother plant and planted as main plant. It is suitable for plants under stolon, creeper, trailer or prostrate like Jasmine, Strawberry, Ipomoea, Clematis etc.
2. Air Layering:
This method is useful for woody plants whose branches cannot be dragged down to soil. This method is normally called as Kalami in Nepali. For preparing layering, a small cut of about 10 cm wide including Phloem, cambium & bark and applying rooting hormone& moist moss or moist cotton or grafting clay: clay: Cow urine: fine pieces of hay @ 2:1:1 wrapping with plastic & tightening with rubber or rope to prevent any moisture loss. After that about 1 to 3 months adventitious roots are developed in the cut part. Now, cut the branch below the injured part where adventitious roots develop then planted as new plant.
Grafting is such a technique in which a cut bud or branch of one plant is inserted in another plant of same or closely related species from which characters of both plants are present in the single plant. Between the two plants one with fixed root system is called rootstock or simply stock and plant from which transplanting part of grafting part is taken is called as scion. This new plant consists of stock as root system & scion as shoot system. It is useful for dicot plants & gymnosperms like Mango, Guava, Mandarian, Lime, Rubber, Dhupi etc. This technique is mainly used in fruit crops for growing different varieties or cultivars in another type of cultivar but related to each other. Nowadays grafting is carried out in Tomato too. During grafting, root system with height 20-30 cm from ground is cut back to make scion compatible to the stock. The joined part is applied with grafting clay around upto 5-7 cm thick supporting with rubber or rope. After few weeks, due to meristematic activity of both scion & stock vascular tissue (xylem & phloem) are connected or fused together & start growing as single plant. Following are the techniques of grafting: –
Tongue or whip grafting:
This grafting is found suitable for scion & stock with similar diameter. In this technique, scion & stock are given a cut of tongue like structure using sharp grafting knife. Now fit the stock & scion tightly & tighten the fitting.
In this technique, v-shaped notch is created in stock & scion is slightly sharpened from both sides to fit in that notch. Note: The diameter of stock & scion must be similar like.
Cleft or crown grafting:
This method is applied in the scion which is very small in diameter with that of stock. Now, more than 2 scions are cut with wedge shaped and stock are made with V-shaped notch and are fitted tightly.
In this technique, single scion with wedge shaped cut is made & v shaped notch is made in stock in the side. Scion & stock are fitted tightly.
In this method, both scion and stock are intact to their own root system. Scion is grown in vase or near to the stock. Bark of both scion and stock are removed at same level and are held tightly applying grafting clay around and tightening with rubber or rope. When they continue to grow as single plant the root system of scion is detached and shoot system of stock is also detached.
In this technique, a long-slit cut is made in stock without affecting xylem. After that, bud of same or closely related species is transplanted in that slit applying grafting clay making bud open and tighten with rubber or rope. After sometimes bud fits with stock and starts growing as single plant. Cut the shoot system of stock 10 cm above the bud grafted area.
Micropropagation is simply propagation through in-vitro culture of vegetative parts of plant which is referred as cloning or clonal propagation. Plant cell or tissue is grown in artificial nutrient medium i.e. MS medium in sterilized condition to a completely new plant.
Advantages of Artificial Vegetative Propagation:
- Plants which cannot produce viable seeds are easily propagated by vegetative propagation. Plants like Banana, seedless grapes, rose, gardenia, sugarcane, chrysanthemum etc.
- Superior quality fruits and flowers can be grown from grafted plants.
- Vegetatively grown plants come to mature earlier than plants grown from seed.
- Disease free numerous plants can be grown in short period of time in micro-propagation technique.
- Plants which cannot bear high number of seeds whose seeds have long period of seed dormancy are easily propagated through this technique.
- Daughter plants will have exact carbon copies of mother plant that means with same bearing capacity and of same quality.