THE EFFECT OF TEMPERATURE AND LIGHT ON GROWTH AND FLOWERING OF ROSA 'BACCARA' IN GREENHOUSES
Some of the buds may remain dormant for a long period of time after pruning. This may also happen after the flower is cut at the normal stage for marketing. Removing leaves adjacent to dormant buds, has been demonstrated to break dormancy. Kamp (1948) found the proportion of blind shoots to increase simultaneously while Durkin (1965) detected less blindness with defoliation. The rate of growth and flower production is positively correlated with the solar radiation (Post and Howland 1946, Chandler and Watson 1954, Farmer and Holley 1954), and the rate of development is positively correlated with the temperature (Boodley and Seeley 1960).
Abnormal colouring of the petals is frequently experienced. 'Baccara' tends to become very dark (blackening) at times. Low temperature has generally resulted in higher anthocyanin content in the plants (Harborne 1967). It is evident that light is required for the synthesis of anthocyanins (Shisa and Takano 1964), and that the nutrition of the plant may modify the colour intensity (Abernathie 1960, Lindstrom and Markakis 1963, Shisa and Takano 1964).
The quality of the cut flower, the strength and the length of the stem, and the size, shape, and colour of the flower, is of great importance in commercial production of roses. However, the literature offers no precise information on the effect of the climatic conditions on the growth and development of the rose shoot. With the intention to work out the optimal temperature regime for roses, several experiments were conducted which will be reported on in the present paper.