Combating ozone stress through N fertilization: A case study of Indian bean (Dolichos lablab L.)

Abstract

The present study investigates the efficiency of nitrogen (N) amendments in the management of ozone (O3) stress in two varieties (Kashi Sheetal and Kashi Harittima) of Indian bean (Dolichos lablab L.). Two O3 concentrations, ambient (44.9 ppb) and elevated (74.64 ppb) were used, and each O3 concentration has 3 nitrogen (N) dose treatments viz recommended (N1), 1.5 times recommended (N2), 2 times recommended (N3) and no nitrogen, which served as control (C). The experiment concluded Kashi Sheetal as O3 tolerant, as compared to Kashi Harittima. N amendments were effective in the partial amelioration of O3 stress, with N2 being the most effective nitrogen dose, at both ambient and elevated O3 concentrations. Kashi Sheetal has been determined to be O3 tolerant due to greater endogenous levels of H2O2 accumulation and enzymatic antioxidant contents with O3 exposure. The O3-sensitive variety, Kashi Harittima, responded more positively to N treatments, at both O3 concentrations. The positive effect of N amendments is attributed to the stimulated antioxidative enzyme activity, rather than the biophysical processes like stomatal conductance. Strengthened defense upon N amendments was attributed to the enhanced activities of APX and GR in Kashi Sheetal, while in Kashi Harittima, the two enzymes (APX and GR) were coupled by SOD and CAT as well, during the reproductive phase. Yield (weight of seeds plant-1) increments upon N (N2) amendments were higher in Kashi Harittima (O3 sensitive), as compared to Kashi Sheetal (O3 tolerant) at both ambient and elevated O3 concentration, due to higher antioxidant enzymatic response and greater rate of photosynthesis in the former.

Role of Elevated Ozone on Development and Metabolite Contents of Lemongrass [Cymbopogon flexuosus (Steud.) (Wats.)]

“…During stress, imbalanced osmotic solute disturbs the K + flux from guard cells, resulting in the modification of guard cell turgidity and stomatal aperture [ 74 ]. A simultaneous decrease in Ps and gs in response to O 3 stress has also been reported in many other studies [ 64 , 65 , 75 , 76 ]. The increase in iCO 2 during EO 1 and EO 2 treatments can be correlated with reduced Ps due to damage to photosynthetic machinery [ 76 ].…”

“…The PCA ( Figure 13 ) also indicated a strong positive correlation of LPO and ROS with O 3 concentrations. Upon O 3 exposure, the increased concentration of MDA contents and ROS, have been commonly reported in earlier studies [ 17 , 65 , 66 , 67 , 68 , 69 ]. Higher plants sustain an efficient enzymatic and non-enzymatic antioxidant pool to cope with O 3 -induced stress.…”

“…Increased malonaldehyde content in O 3 -exposed plants is a result of lipid peroxidation, which suggests a disruption in plasma membrane permeability leading to an unbalance in disrupted cellular homeostasis [ 64 ]. Enhanced lipid peroxidation is attributed to the stimulated production of reactive oxygen species (ROS) such as O 2 −0 and H 2 O 2 [ 65 ] at high O 3 concentrations. It was observed that, in the present study, the magnitude of lipid peroxidation and ROS production increased with increasing O 3 concentration, signifying higher oxidative stress at higher O 3 (AO < EO 1 < EO 2 ) concentrations.…”

“…Notably, a higher increase in the enzyme activity was observed during the second sampling of the EO 1 and EO 2 treatments, as compared to AO treatments, suggesting an efficient stimulation of the defence machinery of lemongrass to combat the O 3 stress at a later developmental stage. The incitement of antioxidant enzymes has also been reported in wheat [ 17 , 62 ], cotton [ 70 ], bean [ 65 ] and castor [ 66 ]. However, in this study, constitutive levels of enzymatic antioxidants were always higher at first sampling stage compared to the second sampling stage in all the treatments, suggesting their utilization of resources in other metabolic pathways during the later developmental stage.…”

Impact of Elevated Ozone on Cabbage

“…Increased malonaldehyde content in O3-exposed plants is a result of lipid peroxidation, which suggests a disruption in plasma membrane permeability leading to an unbalance in disrupted cellular homeostasis [29]. Enhanced lipid peroxidation is attributed to the stimulated production of reactive oxygen species (ROS) such as O2 −0 and H2O2 [30]. Similar increase in MDA contents under ozone stress have been shown in blackgram cultivars [31] and in Grapevines [32].…”