Effects of Salicylic Acid on Some Morphophysiological Characteristics of Border Flowers from Asteraceae Family under Water Deficit

In order to improve physical and mental human healthy, development of the urban area landscape is necessary. Water deficit is one of the most important problems in arid and semi- arid regions. Water deficit causes to reduce growth of different plants parts, including roots, aerial parts, leaf area, height, dry weight, proteins, amino acids and chlorophyll. Using drought tolerance plantsisone solution. Moreover, one physiological method to decrease the hazardous effects of environmental stresses on plants is to applyplant growth regulators such as salicylic acid (SA). SA is one of the plant phenolic compounds in low amounts (mg/g wet weight or lower).
This hormone can perform an important role in resistance to stresses. Asteraceae is one of the biggest plant families with over 20,000 species which is distributed worldwide in moderate and tropical regions. A lot of border flowers of this family are widely used in landscaping. Toselect drought tolerance flowers and application of materials that reducing stress effects, this experiment was conducted to investigate the effects of salicylic acid on some morphological and physiological characteristics of five border flowers of this family.
The field experiment was conducted as split plot on randomized complete blocks design with four replications in which factors included two levels of water deficit (50, 100% FC) as main plot and two levels of SA (0, 1mmol/L-1) as sub plot in the horticulturedepartment of faculty of Agriculture atFerdowsi University of Mashhad. In this investigation five border flowers (Ageratum houstonianum‘Blue Danube’, Tagetserecta ‘Discovery Yellow’, Tagetspatula‘Hero Harmony’, Zinnia elegans ‘Lilliput rose’andCallistephuschinensis ‘Milady Mix’ ) of Asteraceae family were chosen for study. The soil mixture was analyzed before starting the test. According to the result of physicochemical analysis of the soil, it had loamy texture (52% sand, 30% silt and 18% clay) with 7.04 pH and 3.6 ds/m electrical conductivity (EC) and total N (0.175mg/kg), P (142.7 mg/kg) and K (142.3mg/kg) were reported, too. Investigated characteristics were height of the plants, leaf area,flower number,root dry weight, flower dry weight, aerial parts dry weight,chlorophyll a, chlorophyll b, ,total chlorophyll,carotenoide,stomata conductance,relative water content (RWC) and electrolyte leakage. Tomeasureleaf area and stomata conductance, leaf area meter and prometer were used, respectively. In addition, electrolyte leakage, RWC, chlorophyll and carotenoide were evaluated by Sairamet al., Smart and Bingham, Arnon and Rangan methods, respectively. Minitab 16 software was used for data analysis and LSD test (p≤ 5%) for mean comparison was applied.
The results of this study showed that all characteristics of examined flowers decreased underwater deficit treatment (50% FC). SA had different effect on flowers properties. Although SA had not significant effect on flower number, it improved the percentage of characteristicssuch asflower dry weight, chlorophyll a, stomata conductance and RWC of Ageratum houstonianum; root dry weight, carotenoid andstomata conductance of Zinnia elegans; carotenoid of Tagetserecta; flower number, flower dry weight, carotenoid and stomata conductance of Tagetspatula; root dry weight, flower dry weight, aerial parts dry weight andstomata conductance of Callistephuschinensis. Moreover, SA had significant effect on the considered characteristics of the other studied flowers. Interaction effect of these two factors had different effects on all of the examined characteristics of five flowers. The highest amounts of the investigated characteristics mostly obtained from water deficit with SA application treatment. Under water deficit, SA could influence leaf area and electrolyte leakage of all examined flowers and aerial parts dry weight of all flowers except Callistephuschinensis. Among the studied flowersTagetserectaand Zinnia elegans showed the highest and Callistephuschinensisdisplayed the lowest response to SA application under water deficit. Underwater deficit conditions SA probably cause to improve nutritious elements that can increase plant growth. Different effects of SA on morphological and physiological properties may be due to the plant species and environmental conditions that can influence on morphophysiologic process variously.
The results of this studyindicated that SA resulted in the improvement of themost of morphological and physiological properties. However different results obtained,due to the variation in morphological and physiological characteristics of flowers.