Physiological Characteristics of Two Rose Cultivars (Rosa hybrida L.) under Different Levels of Shading in Greenhouse Conditions

In many parts of Iran high light intensities during summer can induce stress in cut flower production under open field and greenhouse conditions. Despite roses prefer sunny places for optimum growth, but in practice some levels of rough shading is applied in greenhouse production to improve the quality of cut flowers. So, it is useful to find the light intensities under which different rose cultivars produce optimum yield with acceptable market quality. In present study, different light intensities were applied for two rose cultivars of ‘Red One’ and ‘Gulmira’, by shading levels of 1200 (without shading as control), 640, 520 and 240 µmol m-2 s-1, using green plastic nets. The result showed that leaf protein concentration, peroxidase activity, petal anthocyanin concentration and carbohydrate levels were significantly different among shade treatments, as the highest protein concentration was observed in 640 µmolm-2 s-1. The highest concentration of anthocyanin of petals was observed in ʻRed Oneʼ under 520 µmolm-2 s-1. Furthermore, in ʻGulmiraʼ the highest amount of anthocynin was in 520 µmol m-2 s-1, but this was not statistically significant compared to other shading treatments. The highest amount of leaf carbohydrate was in 520 µmol m-2 s-1. The results indicate that shading up to a light intensity of 520 µmol m-2 s-1 is beneficial for quality improvement of these rose cultivars when light intensity is high.