OWN-ROOTED ROSE PLANTS ON HYDROPONICS AS RESEARCH MATERIAL

A typical growing cycle of 'Sonia' comprises: rooting period, 2 wk; primary shoot development, until coloured flower bud, 6 wk; secondary shoot ('renewal shoot', from which the next generation of cuttings is made), 6 wk.

With a 2°C cold box as a buffer (for storing both cutting wood and rooted cuttings, if necessary), we routinely grow our material year-round, on a 2–3 wk interval schedule, permanently under artificial conditions: 25°C and low light in the rooting cabinet; 20°C, 75 Wm^-2 and 70% RH in the climate room.

Judging by casual observations (outside the scope of our project on post-harvest physiology of cut roses), we feel this material may offer good possibilities for other types of rose research as well, such as:

• Relationship between position of cutting within mother plant and development of daughter plant, including readiness of renewal cane initiation and sprouting;
• Endogenous/exogenous effects on renewal cane formation;
• Scion/rootstock interaction (cultivars show large differences in growing habit of both shoot and root system, and in root/shoot ratios);
• Temperature and other effects at strictly defined moments of flower-bud initiation and development on ultimate petal number and flower size;
• Endogenous/exogenous effects on flower-bud abortion;
• Various types of flower malformation, and critical period of initiation.

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