Effects of calcium-containing natural fertilizer on Camellia sinensis (L.) Kuntze

Abstract

The effects of application of calcium-containing natural fertilizer on the functional state of the tea plant were studied. Application of calcium resulted weakening of the negative effects of high temperatures and water deficiency due to an increase in its heat resistance (on average by 30 40%), an increase in catalase activity (on average 5 10 %), as well as adaptive rearrangement of pigment ratio to increasing the content of carotenoids, chlorophylls and the their functional activity. In general, the more efficient functioning of the signaling intracellular network due to the calcium application provided better adaptability of plants to extreme conditions and more efficient recovery after subsequent rehydration, which in a whole contributed to an increase in shoot growth activity (on average 20%) and an increase in yield by an average of 27 33%. The Black Sea coast of North-Western Caucasus is the one of the northernmost region where the tea plant is commercially cultivated. This crop was introduced in the region for the first time in 1878. The first tea plantation was founded here in 1901 and commercial propagation has been continuing till now. Tea in Russia, as well as in a several other regions of the world (China, India, Japan) faces such environmental factors as temperature stresses, solar insolation, drought, mineral deficiency which decrease its yield and productivity (Bhagat et al. 2010, Baruahl and Bhagat 2012, Malyukova 2014, Samarina et al. 2017). In this regard, it is important to study the effectiveness of various exogenous inductors (mineral fertilizers, biologically active compounds) to increase resistance and productivity of plants under extreme environmental conditions (Song et al. 2008, Njoloma 2012, Upadhyaya et al. 2012 and Pan Zhu-Cai 2015). Among a wide range of biogenic macroand microelements entering agro-ecosystems with fertilizers, the calcium is of special scientific interest which performs a signal function in the plant organism in the synthesis of stress proteins that provide resistance to unfavorable environmental factors, as well as recovery after stress (Bush 1995, Gao at al. 1999, Shu and Fan 2000, Li et al. 2002, Saidi et al. 2009). It was reported that Ca is involved in regulating such diverse and fundamental processes as cytoplasmic streaming, thigmotropism, gravitropism, cell division, cell elongation, cell differentiation, cell polarity, photomorphogensis, and plant defense and stress responses (Reddy 2000, Malho at al. 2006). It is believed that calcium influx and cytoplasmic calcium ([Ca]cyt) are important for guard cell ABA transduction, while ABA can regulate stomatal aperture in guard cells in many stress responses. In Arabidopsis thaliana the oscillating amplitudes of [Ca]o (extracellular Ca concentration) and [Ca]i (cytosolic Ca concentration) are controlled by soil Ca concentrations and transpiration rates. Enhanced tolerance to temperature stress can also be explained by increased activity of γglutamyl kinase and decreased activity of proline oxidase in plant tissues (Hetherington and Brownlee 2004, Kim 2009). A number of studies have shown the effect of calcium on the reduction of oxidative damage in various plants (including tea) under drought by inducing an antioxidant system (Upadhyaya et al. 2012, Li et al. *Author for correspondence: <[email protected]> 180 MALYUKOVA et al. 2004, Rikhvanov et al. 2014, Medvedev 2015). With prolonged cultivation of tea on naturally acidic soils, soil acidification is usually developed, leading to a significant decrease of available forms of calcium and the formation of a deficiency of this element (Malyukova 2014). Based on the available reports, the goal of the present work was to study the influence of the root application of calcium in the natural form on the functional state of tea and its nutritional status in field conditions with insufficient water supply. Application of calcium containing fertilizers and natural calcium-containing components has environmental and nature restoration effects and will help to improve the supply of plant with this element. Experiments were conducted in the humid subtropical conditions of the Black Sea coast of the North-Western Caucasus (Russia, Sochi city, UchDere district 43,69◦N., 39,64◦E.), wherein the average temperature varies from 12.8 16.5C, annual rainfall of 1313 2098 mm. The growth period lasts from April to October, with the summer rainfall deficit. The observations were carried out during 2011 2017 in field plantations of mature tea plant Camellia sinensis commercial cultivar Kolkhida. The type of soils of the experimental plot is Cambisols, characterized by a high level of fertility and a sufficient number of nutrients for tea plant. The following treatments were laid out in a RBD: T1 control, application N240P70K90 in kg/ha; T2 application N240P70K90 in kg/ha along with a clay-chalk substance (CaO), which was applied at a dose of 100 kg/ha. There were three replications in each treatment. The area of each replication was 10 m. The plants were not irrigated as this is the general practice in this region. As a source of exogenous calcium, a natural material was used a clay-chalk substance. The yields observations were made annually according to the experimental treatments during the periods of the formation of a 3-leaf young tea shoot. The total number of shoots was taken into account, as well as the ratio of different-aged shoots and their mass was carried out on the experimental field sites of 0.25 m at 2 points on each experimental repeat. The content of tannins was determined in the aqueous extracts of tea leaves by volumetric permanganate method of Levintal, based on the oxidation of tannins with the action of 0.1N KMnO4 in the presence of indigosulfuric acid, which acts both as an indicator and a regulator of the reaction. The content of extractive substances was determined by the weighting method according to Vorontsov (Voronzov 1946). The content of photosynthetic pigments (chlorophyll a and b, carotenoids) was determined in 100% acetone extract of fresh leaves using spectrophotometry at 665 nm wavelength for chlorophyll a, 649 nm for chlorophyll b and 440 nm for carotenoids using Ziegler and Egle computational formulas (Shlyk1971). Catalase activity in green leaves was determined gasometrically (Gunar 1972). Assessment of the functional state of the photosynthetic apparatus of tea plants was carried out according to the parameters of slow induction of chlorophyll fluorescence on an LPT-3C device, according to instructions developed by Budagovskaya (Budagovskaya 2001). The efficiency of photochemical reactions was evaluated in terms of the relative fluorescence quenching-viability index (ratio of the maximum fluorescence to the stationary level of chlorophyll fluorescence. Heat resistance was evaluated in the dynamic using leaves according to Kushnerenko (Kushnerenko et al. 1985). The concentration of cell sap (CCS) was assessed by the refractometric method of Filippov (Filippov 1975). The count of microorganisms in the rhizosphere locus of soils (at a depth of 10 20 cm) was measured in the reconstituted samples after storage in a freezer at a ‒18°C by dilution and seeding of soil suspension onto elective media: MPA for bacteria, Gause-1 with the addition of penicillin (1.0 mg/l) and nystatin (50 mg/l) for actinobacteria and acidified Czapek medium for micromycetes (Zvyagintsev 1991). The processing of the experimental material was carried out using the methods of variationdescriptive statistics using the Agrochemistry program. In favorable weather conditions, the yield of tea plant cultivar Kolkhida was on the average of 7200 9700 kg/ha (Table 1) and is comparable to the potential for this cultivar in the mentioned EFFECTS OF CALCIUM-CONTAINING NATURAL FERTILIZER 181 climatic conditions in the region (Malyukova 2014). The seasonal yield varies primarily as a result of seasonal temperature changes and soil drought stress during the dry season. The main part of the tea yield under these conditions was formed fairly evenly, mainly in the period May-early August (Table 2), with a bit advantage of the May harvest. In the unfavorable spring conditions, yield decreased in the May to 22 32% of all harvest. The maximum loss of the total yield (up to 50 60%) was observed in the drought period of July August and was associated with the inhibition of plants by increasing Cell Sap concentration to 11.8 13.8% (when the optimum was 8 9%) and decreasing in shoot-growth ability (Tuov et al. 1997, Malyukova et al. 2016). Table 1. Total yield of Kolkhida tea cultivar in various meteorological conditions. Variant Yield average (kg/ha) Increase of yield (%)