Effects of Cycocel on Morphological Traits, Nitrogen and Potassium Content of Basil Plants under Water Stress Conditions

Introduction Basil (Ocimum basilicum) is an annual plant which belongs to the Lamiaceae family. It used as a drug, spice and fresh vegetable. Drought stress is one of the important limiting factors of plant growth. Water stress has significant effects on morphological and biochemical characteristics of purple Basil. As the soil water content decreases, the plant height, stem diameter, number and area of leaves, leaf area index (LAI), herb yield and leaf chlorophyll contents (a,b and total chlorophyll) decrease, as well. However, the amounts of anthocyanin and proline increase. Cycocel (CCC) which chemically called chlormequat chloride is an alkylating agent and a quaternary ammonium salt.. Cycocel is used as plant growth regulator. Application of Cycocel increases the number of siliques/ plant, seed yield and dry matter produced of oilseed rape. Cycocel application decreases the plant height and increases the yield level and protein percentage of seed in faba bean. This research was performed to investigate the effect of Cycocel on morphological characteristics, the percentage of nitrogen and potassium of basil plants under drought stress conditions Materials and Methods This research has been conducted in the research station of Shahid Bahonar University of Kerman with 56o 58' E longitude, 30o 15' N latitude, and 1753.8 altitudes. According to the regional information from 1952 to 2005, the average temperature was 17.1 o C, the average rainfall was 154.1 mm, the average annual relative humidity is 32%, and the climate of Kerman according to De Martonne method is semiarid. A split plot experiment based on RCBD with three replications was employed. Three levels of irrigation, including 50 (severe stress) (I3), 75 (mild stress) (I2) and 100 (full irrigation) (I1) percent of crop water requirement were assigned to the main plots while five levels of Cycocel application (zero (control), 500, 1000, 1500, 2000 milligrams per litre) were assigned to the sub-plots. Cultivation was carried out in March and harvested in late June. In this study the plant height, fresh and dry weight of root and shoot, root to shoot dry weight ratio, percentage of nitrogen and potassium, leaf relative water content and leaf area index were measured. For its statistical calculation, SAS (v. 9.1) software and for the comparison of the averages the Duncan’s test was used. The level of possibility used in the analysis was five percent. Results and Discussion The result of the analysis of variance of measured traits has shown in Table 1. Data analysis of variance (Table 1) shows different levels of irrigation, Cycocel and irrigation with Cycocel interaction were significant at the level of one percent on plant height. Effects of different irrigation treatments and Cycocel concentration on fresh and dry weight of shoot were significant at one and five percent, respectively. However, the effect of irrigation and Cycocel interaction on shoot dry weight was not significant. Root fresh and dry weight were influenced by irrigation levels (Table 1). The effect of irrigation and Cycocel interaction on root dry weight, percent of nitrogen and dry weight of root to shoot ratio was significantat one percent. The effect of irrigation on root to shoot dry weight ratio was not significant. Moreover, the effects of Cycocel treatments on root to shoot dry weight ratio were significant at the five percent level. The effect of irrigation, Cycocel on percent of nitrogen and potassium was significant and potassium decreased with the increasing of water stress. The highest percentage of potassium (2.26%) belonged to the full irrigation and the concentration of 2000 milligrams per litre Cycocel and the lowest belonged to the interaction of severe stress and zero, 500 and 1000 milligrams per litre Cycocel. Irrigation and Cycocel had a significant influence on leaf relative water content at the level of one percent. Conclusions According to the results which obtained through this study, in basil plant, root fresh and dry weight, shoot fresh and dry weight, leaf area index, leaf relative water content and plant height reduced by increasing drought stress. Root-shoot dry weight ratio increased in response to increasing stress in all the plants which treated by Cycocel . Cycocel treatments reduced plant height, root fresh and dry weight, shoot dry weight and LAI. Leaf relative water content and shoot fresh weight increase with increasing the concentrations of Cycocel. The interaction of 2000 milligram Cycocel per litre with irrigation has the greatest effect on the traits