Morphological, physiological, and biochemical responses of onion (Allium cepa L.) breeding lines to single and combined salt and drought stresses

Abiotic stresses deteriorate plant growth resulting in devastating yield losses. Salt stress solely cause ionic toxicity and disturbed homeostasis, whereas combined salt and drought stress has more pronounced effects on plants. Here we performed a pot experiment using 32 Turkish onion breeding lines and commercial cultivars for screening against salt, drought and combined salt and drought stress treatments initiated at the bulbification stage under greenhouse conditions. Physiological characteristics, such as gaseous exchange traits, chlorophyll index, leaf temperature, and morphological traits including number of leaves, length and diameter of leaf were measured during stress treatment and yield response of the onions was quantified by measuring bulb length, bulb diameter and bulb weight after harvest. Proline and malondialdehyde accumulation were estimated for biochemical effect of stress on onion genotypes. All genotypes responded differentially to the applied single and combined stresses. Overall results revealed that the breeding lines K25, U6, U17 and commercial cultivar K58, were grouped as sensitive across all stresses, whereas the breeding lines K41, U47, U49 and commercial cultivar K52, were found to be the most stable upon stress. These resilient genotypes can be used as breeding material for future abiotic stress studies.

STUDY OF KINETIN TRAETMENT ON GROWTH AND ACTIVITY OF SOME ANTIOXIDANT ENZYMES OF SPINACH UNDER SALT STRESS

Soil salinity reduces water availability of plant roots via negative (low) osmosis potential, as well as decrease of germination dynamics of plant seeds by ionic toxicity of Na and Cl, Significant differences in fruit-set, yield, photosynthetic rates, stomatal conductance, total chlorophyll content, proline, In general, salinity affects almost every aspect of the physiology and biochemistry of plants. This experiment was conducted on a private farm in Babylon Governorate at the period from 1/10/ 2013 to 15/5/ 2014, to study the effect of Kinetin treatment with three concentrations (0, 20 & 40 mg /liter ) and the quality of irrigation water in three levels ( 1.3 , 5 & 10) dS.m-1 the water salinity increased the POX and CAT activity, sodium and proline contents in leaves, resulting in decreased growth and leaf contents of NPK, The Kinetin applications alleviated negative effects of saline water by increasing dry weights of roots and NPK contents in leaves with an increasing of POX and CAT activity, and reduction of sodium contents in leaves.

The effect of manganese(II) excess on growth and antioxidant status of barley seedlings

Manganese belongs to the group of heavy metals, which at high concentrations can have a negative effect on plant development. Typical soils of the Kirov region are acid podzolic and sod-podzolic soils, which are characterized by high content of manganese compounds available for plants. Studied was the effect of manganese(II) ions at the concentrations of 30.0, 60.0 and 90.0 mg/l on the growth and antioxidant activity (AOA) of the superoxide dismutase enzyme (SOD) in the organs of 7 and 14-day-old barley plants grown in aquatic culture. Varieties and forms of barley 346-09, 29-11, Farmer 198-12, Forward and Bionik, resistant to acidic soils (Al3 +, H+) served as objects for the research; Belgorodskij 100 variety was used as standard. When manganese was added to the solution for growing, a decrease in root length and an increase in AOA of SOD in plant roots were noted. It was concluded that increased concentrations of manganese had an effect on the morphometric parameters and on AOA SOD of barley seedlings. It has been established that increasing the dose of manganese in the solution for growing leads to a decrease in the length of the roots. AOA SOD varied in different organs of plants of some varieties, and its more significant change in the experiment compared with the control was revealed in the roots. Judging by morphometric indicators, the Belgorodskij 100 variety was the least resistant to Mn2+ ionic toxicity, the root length of which in the control was 15.7±0.4 cm, and in the experiment 13.2±0.3; 12.2±0.1; 11.5±0.3 cm in accordance with the dose of manganese 30, 60 and 90 mg / l. According to the level of AOA SOD, the most sensitive variety was Farmer 198-12, its change of AOA SOD in the roots (% of control) was 158.8; 167.2 and 169.4% in accordance with the dose of manganese 30.0; 60.0 and 90.0 mg / l (AOA SOD in the control was 52.4±0.4%; in the experiment 83.2±2.2; 87.6±2.0 and 88.7±0.6, respectively), and in the shoots ˗ 121.0; 128.3 and 125.6 %, respectively (66.7±7.9 % in the control and 80.7±0.5; 85.6±1.4; 83.8±0.6 % in the experiment in accordance with the dose of Mn 2+).

Toxicity analyses of surface water in selected industrial areas of Bogura sadar, Bangladesh

An investigation was carried out to assess the extent of ionic toxicity of surface water samples for agricultural usage in the Karatoya-Bangali Floodplain (2,577 sq. km). Fifteen water samples were collected from five industrial areas of Bogura sadar upazila to assess the dissolved chemical constituents and also to classify them on the basis of their comparative stability for agricultural usage. Water samples were collected from surface water sources viz., rivers, canals and ponds at Bogura sadar upazila. The chemical analyses included pH, electrical conductivity (EC), total dissolved solids (TDS), Ca, Mg, K, Na, Zn, Cu, Fe, Mn, Cd, Pb, B, As, CO3, HCO3, PO4, SO4 and Cl. The pH indicated that surface water samples were acidic to alkaline in nature (pH = 6.5-8.8). The electrical conductivity (EC) and sodium absorption ratio (SAR) revealed that all the surface samples were categorized as ‘medium salinity’ and ‘low alkalinity’ hazards with ‘excellent’ and ‘good’ in quality combining expressed as C2S1. Considering TDS all the surface waters were as ‘freshwater’. Soluble sodium percentage (SSP) indicated that all the surface water samples were ‘excellent’ and ‘good’ classes. Residual sodium carbonate (RSC) categorized the surface water samples as ‘suitable’ in quality for irrigation. The status of Ca, Mg, Na, K, Zn, Cu, As, B, Fe, CO3, SO4, PO4, and Cl were not hazards in the investigated area. In all surface water samples, HCO3 ion was considered as pollutant for irrigating crops. Rest ionic constituents were suitable for irrigation purposes. As, B, SO4, Cl and TDS were not problematic for drinking, TDS, Cd, Cu and Zn were not hazardous for livestock usage and SO4 and hardness (HT) were not problematic for aquaculture. But rest ionic constituents for these respective usages were toxic. Res. Agric., Livest. Fish.6(2): 227-234, August 2019

Quercetin Mediated Salt Tolerance in Tomato through the Enhancement of Plant Antioxidant Defense and Glyoxalase Systems

Quercetin (Qu) is a strong antioxidant among the phenolic compounds having physiological and biochemical roles in plants. Hence, we have studied the Qu evolved protection against salinity in tomato (Solanum lycopersicum L.). Salinity caused ionic toxicity by increasing Na+ content in seedlings along with nutritional starvation of K+, Ca2+, and Mg2+. While osmotic stress was detected by higher free proline (Pro) content and lower leaf relative water content (LRWC) in salt-stressed seedlings. Salt toxicity also induced higher H2O2 generation, malondialdehyde (MDA) content and lipoxygenase (LOX) activity as a sign of oxidative stress. Tomato seedlings suffered from methylglyoxal (MG) toxicity, degradation of chlorophyll, along with lower biomass accumulation and growth due to salt exposure. However, Qu application under salinity resulted in lower Na+/K+ due to reduced Na+ content, higher LRWC, increased Pro, and reduction of H2O2 and MDA content, and LOX activity, which indicated alleviation of ionic, osmotic, and oxidative stress respectively. Quercetin caused oxidative stress, lessening through the strengthening of both enzymatic and non-enzymatic antioxidants. In addition, Qu increased glutathione S-transferase activity in salt-invaded seedlings, which might be stimulated reactive oxygen species (ROS) scavenging along with higher GSH content. As a result, toxic MG was detoxified in Qu supplemented salt-stressed seedlings by increasing both Gly I and Gly II activities. Moreover, Qu insisted on better plant growth and photosynthetic pigments synthesis in saline or without saline media. Therefore, exogenous applied Qu may become an important actor to minimize salt-induced toxicity in crops.

Seasonal and multiannual effects of salinisation on tomato yield and fruit quality

The effects of short- and long-term salinisation were studied by comparing tomato growth on a soil exposed to one-season salinisation (short term) vs growth on a soil exposed to >20 years salinisation (long term). Remarkable differences were associated to substantial modifications of the soil physical-chemical characteristics in the root zone, including deteriorated structure, reduced infiltration properties and increased pH. Fresh yield, fruit number and fruit weight were similarly affected by short- and long-term salinisation. In contrast, the marketable yield was significantly lower in the long-term salinised soil – a response that was also associated to nutritional imbalance (mainly referred to P and K). As reported for plants growing under oxygen deprivation stress, the antioxidant capacity of the water soluble fraction of salinised tomato fruits was enhanced by short-term salinisation, also. Overall, long-term salinisation may cause physiological imbalances and yield reductions that cannot be solely attributed to hyperosmotic stress and ionic toxicity. Therefore, the ability of plants to cope with nutritional deficiency and withstand high pH and anoxia may be important traits that should be considered to improve plant tolerance to long-term salinised soils.