Diurnal Variations in Physiological Characteristics, Photoassimilates, and Total Ascorbate in Early and Late Sown Indian Wheat Cultivars under Exposure to Elevated Ozone

Rising tropospheric ozone (O3) in the atmosphere is detrimental to crop’s productivity and is one of the reasons for a warmer climate. The present study describes diurnal changes in gaseous exchange, chlorophyll fluorescence, ascorbic acid, and photoassimilate parameters in flag leaves of four Indian wheat (Triticum aestivum L.) cultivars (two early sown and two late sown cultivars) under ambient and elevated O3 treatments, using the open-top chambers (OTCs). Results showed that the diurnal pattern of photosynthetic rate (Ps), sucrose, and ascorbic acid content varied according to changes in photosynthetically active radiation (PAR) and O3 concentrations during the daytime and were maximum between 10:00 to 12:00. The present study suggested that elevated O3 caused more negative effects on photosystem II in early sown compared to late sown cultivars. The greater loss of photosynthesis led to lower production of photoassimilates in early sown cultivars, which utilized more assimilates in ascorbic acid formation for detoxification of ROS formed due to elevated O3. This work will also help to identify the robustness of physiological machinery in different wheat cultivars under elevated levels of O3, and may be used for selection of suitable cultivars during future breeding programs.

Response of rice (Oryza sativa L.) cultivars to elevated ozone stress

The current study aimed to evaluate the cultivar specific variation in rice exposed to elevated ozone. Fifteen short duration rice cultivars were exposed to 50 ppb ozone for 30 days at reproductive stage. The physiological, biochemical, growth and yield traits of all test cultivars were significantly affected in response to elevated ozone. On average, ozone stress decreased tiller number by 22.52%, number of effective tillers by 30.43%, 1000 grain weight by 0.62 % and straw weight by 23.83% over control. Spikelet sterility increased by 19.26% and linear multiregression 3D model significantly fits the spikelet sterility and photosynthetic traits with the R 2 of 0.74 under elevated ozone. Principal Component Analysis with total variance of 57.5% by first two principle components categorized 15 rice cultivars into four major groups, ie., ozone sensitive (MDU6, TRY(R)2 and ASD16), moderately ozone sensitive (ASD18, ADT43 and MDU5), moderately ozone tolerant (ADT37, ADT(R)45, TPS5, Anna(R)4, PMK(R)3 and ADT(R)48) and ozone tolerant (CO51, CO47 and ADT36).

Seasonal variation of ozone vertical profiles form ExoMars TGO and comparison to water

<p>The Ultraviolet and Visible Spectrometer (UVIS) channel [1] of the Nadir and Occultation for Mars Discovery (NOMAD) instrument [2] aboard the ExoMars Trace Gas Orbiter has been making observations of the vertical, latitudinal and seasonal distributions of ozone.  Here, we present ~1.5 Mars Years (MY) of vertical profiles of ozone, from <em>L</em><sub>S</sub> = 163° in MY34 to <em>L</em><sub>S</sub> = 320° in MY35.  This period includes the occurrence of the MY34 Global Dust Storm. The relative abundance of both ozone and water (from coincident NOMAD measurements) increases with decreasing altitude below ~40 km at perihelion and at aphelion, localised decreases in ozone abundance exist between 25-35 km coincident with the location of modelled peak water abundances. High latitude (> ± 55°), high altitude (40-55 km) equinoctial ozone enhancements are observed in both hemispheres (<em>L</em><sub>S</sub> ~350‑40°).  Morning terminator observations show elevated ozone abundances with respect to evening observations, most likely attributed to diurnal photochemical partitioning along the line of sight between ozone and O. The ozone retrievals presented here provide the most complete global description of Mars ozone vertical distributions to date as a function of season and latitude</p>