ENVIRONMENTAL CONDITIONS FOR ROOTING CUTTINGS: IMPORTANCE, MEASUREMENT AND CONTROL

For successful rooting, cuttings must survive in a healthy, turgid condition. Their difficulty in replacing transpired water by uptake through a cut stem base, necessitates environmental conditions that discourage water loss. In practice, many plant losses arise through inadequate tissue turgor. To achieve low rates of transpiration, cool leaves which are preferably lightly wetted and with reduced stomatal openings, still conditions, and a low atmospheric vapour deficit are desirable. A wide variety of systems have been developed for this purpose. Unfortunately, a means of measuring their relative effectiveness in an integrated fashion has been lacking. A potential transpiration sensor for this purpose is described here and is used to compare existing systems. The sensor can be used in a control mode to operate mist, fogging or shading and is superior to existing controllers relying on measurement of a single environmental component. The further need to ensure adequate provision of carbohydrates for root formation and growth is also discussed, as is the provision of favourable base temperatures.