Mitigation of Drought Stress Effects on Pepper Seedlings by Exogenous Methylamine Application

Abstract

The study was conducted to determine effects of a new synthesis of methylamine on the plant growth, physiological and biochemical characteristics in pepper under drought stress. There were four irrigation levels [full irrigation (100%) (I0), 80% (I1), 60% (I2) and 40% (I3)] and two methylamine (MA) treatments (0, 2.5 mM). At the end of the study, it was observed that there were significant differences between applications and levels. Effects of MA treatments on plant growth (plant height, stem diameter, fresh, dry weight etc.), plant physiological and biochemical parameters [tissue electrical conductivity (TEC), tissue relative water content (TRWC), hydrogen peroxide (H2O2), malondialdehyde (MDA), proline, antioxidant enzyme activity], and plant nutrient element content of pepper seedlings under different irrigation levels were significantly important. The results of the study showed that the drought stress conditions negatively affected the plant growth, increased the content of TEC, H2O2 and MDA, and decreased the TRWC and plant mineral content in pepper. However, MA application improved plant growth and decreased TEC, H2O2 and MDA content compared to control in pepper under drought conditions. MA treated plants at I3 had higher shoot fresh weight and shoot dry weight than non-treated plants by 12 and 20%, respectively. In conclusion, MA application could mitigate the deleterious effects of the drought stress on the pepper seedlings. Introduction The decrease in water resources has reached to a level that negatively affects the sustainable life as well as the damage caused to the environment. Due to the major environmental stress factors that limit crops productivity, it is becoming increasingly difficult to find suitable areas for plant production. Plants encounter various stress conditions throughout their life cycle. Drought stress is one of the most common abiotic stresses affecting growth and yield, and it has been determined that it activates many protection systems at physiological, biochemical and molecular levels in plants. Drought prevents the growth of the plant as a result of the effect of decreasing the division, growth and turgor pressure of the cells. Drought conditions also negatively affect the transpiration, which may lead to decrease of mineral material intake and decrease of growth rate [1-3]. Water is one of the indispensable growth factors for successful vegetable growing. Vegetables need water for normal vegetative and generative growth and development. Short-term water stress of vegetable crops causes them to close stomata to reduce water loss from the leaves. However, in the event of a long-term drought, irreversible damage occurs in plants and eventually death occurs [4]. There are various organic osmolytes and other compatible solutes. These are sugars (e.g. trehalose), polyols (glycerol, inositols, sorbitol, etc.), amino acids (glycine, proline, taurine, etc.), methylamines [such as Ntrimethylamine oxide (TMAO) and glycine betaine] [5]. Osmolites like methyl ammonium compounds are small molecules that accumulate by cells to prevent denaturing stresses. These osmolites help protect the structural and functional integrity of the macromolecules in animals, protecting cells from hostile stress [6]. Polyamines are small ubiquitous poly-cations involved in many plant growth and development processes and are well known for their anti-aging and anti-stress effects due to their acid neutralization and antioxidant properties as well as their membrane and cell wall stabilization International Letters of Natural Sciences Submitted: 2019-03-25 ISSN: 2300-9675, Vol. 76, pp 111-123 Revised: 2019-04-12 doi:10.18052/www.scipress.com/ILNS.76.111 Accepted: 2019-04-13 2019 SciPress Ltd, Switzerland Online: 2019-08-06 SciPress applies the CC-BY 4.0 license to works we publish: https://creativecommons.org/licenses/by/4.0/ capabilities. Polyamines in plants are effective in growth and development events such as cell division, root formation, adventitious shoot formation, flower formation, fruit ripening and embryo formation in tissue culture [7]. Polyamines have been suggested to play an important role in controlling defense responses to various environmental stresses including metal toxicity [8], oxidative stress [9], drought [10], salinity [11] and low temperature stress [12, 13] in plants. However, to our best knowledge, there is no information on the effects of methylamine on plant growth, some physiological and biochemical properties of pepper seedlings under drought stress in plants. Irrigation is essential for the production of peppers since pepper is considered as one of the most sensitive vegetable species to water stress [14-16]. This study was conducted to determine the effects of methylamine on plant growth, some physiological and biochemical properties of pepper seedlings under different irrigation regimes. Materials and Methods This study was carried out under controlled greenhouse conditions at Atatürk University in 2017. Pepper (Capsicum annum L. cv. Menderes Kıl Acı) was used as plant material. Sterilized seeds were sown to 1 cm deep in 216-celled trays filled with peat: perlite (3: 1 v: v). After 30 days from planting, healthy seedlings were transferred to pots with mixture of garden soil and sand (2: 1, v:v). The soil used in the experiment had 26.3% sand, 33.2% silt, and 40.5% clay. Soil chemical characteristics were as follows: soil pH 7.65; organic matter 1.1%; P; 4.02 mg P2O5 per 100 g soil and K 111 mg K2O per 100 g soil. The weight of all the pots was adjusted to be 2,300 g. The pots were randomly put on the benches in the greenhouse. The temperature and humidity of the greenhouse were monitored daily. The average minimum temperature was 18.7 ° C and the average maximum temperature was 34.1 °C and the humidity was 55%. Methylamine (MA) used in the study is a new synthesis polymer developed by Prof. Dr. Metin Turan who works in Department of Genetics and Bioengineering at Yeditepe University. A new methyl amine molecule were synthesized from the composition of sarcosine, trimethylamine N-oxide (TMAO), and betaine as methyl-amine, which exact formulation of the synthesis composition has not been reported since it has a patent potential (Fig. 1). MA solutions were prepared at levels of 0 (control) and 2,5 mM in pure water. We chose this concentration (2,5 mM) because it was the best concentration in another project we made in squash under drought stress. The roots of seedlings were immersed into the corresponding solutions of MA before transplanting for 5 minutes. One week after transplanting, 200 ml of the same solutions were drenched to roots of the plants. Figure 1. A new methyl amine molecule were synthesized from the composition of sarcosine, trimethylamine N-oxide (TMAO), and betaine as methyl-amine 112 ILNS Biostimulation and Overcoming the Abiotic Stresses in Plants