The monitor and prediction of crop developmental stages, particularly harvest time, play an important role in planning greenhouse cropping programs and timetables by cut rose producers. There have been many scientific reports on the application of image analysis technology in estimating greenhouse crop growth stages. In the present research, we studied leaf color variations over time by taking timely images from four commercial rose cultivars and processing them later using image j software in RGB color space. Results revealed a higher correlation between the leaf color variations and the stages of stem growth in both white color (R2=0.89) and colorful cultivars (R2=0.94). Furthermore, it was determined that there was a significant difference in leaf color components within stem layers in all cultivars. A good correlation was also observed between the leaf total chlorophyll measured directly by spectrophotometric method and the data acquired indirectly from SPAD readings. Among the models fitted to the stem height and color variation data, linear and exponential models performed best. However, some differences were observed between the cultivars. The potential observed in image analysis technique in detecting color differences among the leaf layers and its versatility in non-destructive determination of a link between the leaf color changes and rose stem growth give it the utmost merit and applicability in greenhouses. Developing such a model for other important cultivars of greenhouse roses will make it possible to equip rose greenhouses with several powerful and reliable tools in order to assist the growers to precisely adjust the crop harvest time and accurately plan their operations according to the market demand and policy. Manuscript profile

Light Emitting Diodes (LEDs) can be used as a tool to control the quality of plants in order to meet the requirements of the market by accurately schedule uniform flowering based on a predetermined market date. The aim of this study was to investigate the effect of different light qualities of red (R), blue (B), and UV-A (UV) provided by LEDs, and white light produced by fluorescent lamps (FL) on growth, morphology and flowering characteristics of African violet (Saintpaulia ionantha Wendl.). An experiment was conducted in controlled environment growth chambers at 25 °C. Three ratios of R:B (1:0, 3:1, 0:1) and FL (14 h/d) were used as all-day treatments and UV LED (2 h/d) was supplemented for three ratios of R:B (1:0, 3:1, 0:1) and FL (14 h/d) as end of day (EOD) treatment. Statistical analysis showed addition of B to light spectrum inhibited abnormal leaf growth and promoted compactness. Flowering under FL treatment was distinctly inferior as measured by the number of floral buds, full blooms and inflorescences. However, addition of EOD UV plus R3B1 contributed to higher production of floral buds and full blooms in a short period of time. Supplementing UV light to LED treatments resulted in accelerated leaf expansion. Generally, supplemental UV plus R or B was an acceptable energy-efficient alternative for improving quality of African violet. Vegetative and reproductive phase of Saintpaulia were a function of light quality which could assist the predictability of flowering time in controlled environment systems. Manuscript profile