Mist Propagation Technique
One of the major problem in the propagation of plants by soft wood herbaceous cuttings and leaf cuttings is the loss by wilting due to desiccation before the production of roots by cuttings. In other situations, for example, when atmospheric temperature rises suddenly after the rooting, the young roots become unable to absorb moisture from the soil at a rate at which the newly rooted cuttings start to die due to moisture loss by the transpiring surface of the young leaves. The result of in such situation is again desiccation and death of the young rooted cuttings. Even for the rooting of hardwood cuttings, they should also be maintained in fully turgid condition during the rooting period for a high rooting success. This can be accomplished by keeping the relative humidity of the air surrounding the cuttings at a high level (usually 90-95%) by manual sprinkling of water on foliage several times a day during rooting period. Such procedures are difficult and costly and they usually fail to avoid heat build up in the propagation chamber.
Also read: Method of propagation
To achieve this end water is added to the air of propagation chamber by a number of mechanical means. Usually water is let into the chamber air through suitably designed nozzles under pressure (150-500 lbs per square inch, a high pressure system or 30-70 lbs per square inch a low pressure system) to form a fog or mist in the propagation chamber. This type of mechanism creates and maintains a thin layer of water on leaf surface. It lowers the transpiration rate and thus prevent wilting, desiccation and death of soft leafy cuttings and helps in promoting rooting and subsequent vigorous growth of the roots.
The mist system consists of a regular water source, water strainers, electrically operated day-night timer, time interval cyclic timer, magnetic solenoid valve, mist nozzles and provision for bottom heat in the rooting beds. This type of intermittent mist operates automatically and maintains the chamber at proper humidity and temperature to facilitate rooting. The quality of irrigation water used in the mist system is very important. It should be very low in salt to avoid salt deposition on leaves cuttings and also to prevent clogging of nozzles and lines. This is particularly important in arid regions when salts are usually high in water.
Different kinds of nozzles are available in the market to regulate thr delivery of water into the propagation chamber air. Oil burner nozzles operate best at pressure higher than 150 lb/m², the others operate at pressure less than 100 lb/m² and are usually employed for mist formation where excessive watering is necessary. High pressure nozzles are more costly than the low pressure nozzles. The arrangement on nozzles in the chamber will depend upon objective, local conditions, and arrangement of benches and greenhouse structure. Above propagation benches, nozzles spaced every 3-4 feet will be satisfactory. The length to which a mist line can be expended shall depend upon the pressure of water source. But usually, the length of mist chamber is 100 feet or lesser.
Factors for successful graftage
The different factors for the successful vegetative propagation through budding and grafting are as follows:
Th stock and scion should preferably belong to the same species or genus of the family.
Rootstock should be well suitable and compatible with different scion varieties.
Perfom the budding and grafting when rootstock is in active stage.
The thickness of the rootstock and scion should be same.