The effect of Paclobutrazol and Trinexapac-ethyl on morphological and physiological characteristics of Rosmari (Rosmarinus officinalis) and Thuja (Thuja orientalis Morgan) as two hedging plants

In recent years application of plant growth regulators especially growth retardants, has been significantly increased. Trizols (paclobutrzol and trinexapac-ethyl) as the most effective and least harmful growth retardants, induce more dwarf and denser cover plants with both darker and thicker leaves. Therefore, an experiment based on completely randomized block design with 16 treatments and 3 replicates, was conducted to investigate the effect of paclobutrzol and trinexapac-ethyl application on morphological and physiological characteristics of rosemari and thuja “Morgan” as two hedge plants. Immediately after pruning, foliar spray was applied on each plant with 1000 and 4000 mg/l of paclobutrzol or 1000 mg/l of trinexapac-ethyl. Distilled water was used as control. Measured traits were included plant height and width, wet and dry weight of pruned parts, internode elongation, proline content, chlorophyll a, chlorophyll b and total chlorophyll content. Results indicated that growth retardants decreased plant height and width, wet and dry weight of pruned parts and internode elongation, while they increased proline content, chlorophyll a, chlorophyll b and total chlorophyll content as compared to the control plants.