Effects of Foliar Spraying with Salicylic acid and Putrescine on Growth Characteristics and Yield of Summer Savory (Satureja hortensis L.)

IntroductionSummer Savory (Satureja hortensis L.) is an annual, herbaceous plant belonging to the Labiatae family. This plant is most often used as a culinary herb, but it also has marked medicinal benefits, especially upon the whole digestive system. The most important components of S. hortensis include volatile oils, phenolic compounds, flavonoids and phenolic acids, tannins, mucus, resins, carotenoids and mineral components. Plant growth regulators are used to improve the quality and quantity of medicinal plant production. Salicylic Acid is one of this PGRs that involved in seed germination, photosynthesis, Stomatal opening and closure, Membrane Permeability, Ions Absorption and transmission and other growth processes. Polyamines are ubiquitous low-molecular-weight aliphatic amines that are involved in regulating plant growth processes. The most commonly found polyamines in higher plants, putrescine (Put), spermidine (Spd) and spermine (Spm) may be present in free, soluble conjugated and insoluble bound forms. It has been demonstrated that PAs are important for the normal course of diverse plant ontogeny processes such as cell division and elongation, organogenesis and somatic and zygotic embryogenesis.Materials and MethodsThis experiment was conducted in factorial based on a randomized complete block design with three replications in Karaj, Iran. Foliar spraying with SA (1, 2 and 3 mM.l) and Putrecine (50, 100, 150 and 200 mg l-1) was performed in thrice in Savory growth period. Spraying was performed at 21, 35 (Budding Phase) and 56 (flowering initiation phase) day after seed germination. In flowering stage, some morphological traits such as plant height, weight, yield, canopy diameter, stem diameter, leaf area, essential oil content and efficiency were measured. Results and DiscussionAnalysis of variance showed that the effects of salicylic acid and putrescine spraying on plant height, canopy diameter, stem diameter, number of axillary stems, foliage dry weight, foliage yield, flower dry weight, number of leaves, leaf dry weight, leaf yield, leaf area index (LAI), number of inflorescence, dry weight of inflorescence, total chlorophyll content, chlorophyll a and b content, essential oil content, yield and efficiency was significant (P< 0.01). Application of 100 mg.l putrescine resulted in maximum plant height (45.67 cm) that showed a significant difference with control and 1 mM.l SA treatments. Highest number of inflorescence per plant obtained in pots spraying with 150 and 200 mg.l putrescine and 3 mM l-1 SA. It seems that spraying with putrescine improved vegetative growth through production enhancement of biosynthetic enzymes. Putrescine increased the cell division in plant tissues due to the presence of nitrogen in its structure. Treatment with putrescine significantly improved plant height in Matthiola incana. In response to spraying with 3 mM.l SA amounts of stem diameter, number of leaves per plant, dry weight and yield of leaves and number of inflorescences were significantly increased in comparison with other treatments. Highest values of axillary stems, dry weight of aerial parts, weight of flowering stems, leaf area index and inflorescence yield were also observed in 3 mM l-1 treatments but it did not show significant deference with any of the other treatments. It was well documented that salicylic acid exert their influence on physiological and biochemical processes, including, photosynthesis, ion uptake, membrane permeability, enzyme activities, flowering, heat production and growth and development of plants. SA can increase growth parameters in Summer Savory by enhancing photosynthetic rate and nitrate metabolism. SA increased the activity of nitrate reductase both in leaves and roots of maize plants. Maximum total chlorophyll content was obtained in plants, spraying with 1 and 3 mM l-1 SA that was significant. Application of 1 and 3 mM l-1 SA resulted in higher amounts of chlorophyll a and b, respectively. Moreover, all putrescine concentrations eventuated to significant increase in chlorophyll contents compared to control treatments. Talaat (33) reported that foliar application of putrescine increased chlorophyll and carotenoids content, soluble and non-soluble sugar, proteins and alkaloids in sweet pepper. Based on Figure 2, it was clear that the yield of aerial parts and flowering stems gradually increased with addition of SA concentration and reached its maximum at the 3 mM l-1 treatment. However the significant difference between putrescine concentrations was not observed. ConclusionsThis study revealed that foliar application of SA and putrescine significantly affected the morphological, physiological and biochemical traits of Satureja hortensis. Thus, it can be used as a plant growth regulator for yield and essential oil content improvement in field production of this plant.