Effects of ozone on the photosynthetic apparatus and leaf proteins during leaf development in wheat

Abstract

Leaves of Triticum aestivum cv. Avalon were grown in an atmosphere that contained 150 nmole mol"* ozone for 7 h each day. After leaves had reached maximum size, the leaf blade was divided into three sections to provide tissue of different age, the youngest at the base of the blade and the oldest at the leaf tip. The ozone treatment was found to decrease significantly the light-saturated rate and quantum yield of CO2 assimilation and the maximum quantum yield of photosystem II photochemistry in the oldest leaf section. No effects were found on the basal and middle sections of the leaf. These ozone-induced decreases in the photosynthetic parameters were associated with decreases in the efficiency of utilization of light for CO2 assimilation at the photon fiux density under which the leaves were grown. The depression in photosynthetic performance of tissue near the leaf tip was accompanied by large decreases in the contents of total, soluble and thylakoid proteins and chlorophyll. There was also found to be a preferential loss of ribulose-l,5-carboxylase-oxygenase. These ozone-induced changes in chlorophyll and protein contents and the photosynthetic activities of the leaf tissue were similar to changes normally associated with leaf senescence. Two-dimensional polyacrylamide gel analyses of leaf proteins demonstrated the loss of some minor, and unidentified, proteins, whilst another group of minor proteins appeared. It is concluded that daily exposure of the leaf to 150 nmolmoP^ ozone for 7h had no effect on the development of the photosynthetic apparatus and its activities during leaf expansion, but it did promote the onset of premature senescence in fully expanded tissue that resulted in a loss of pigments, proteins and photosynthetic capacity and efficiency.

Influence of plant age on ozone resistance in Plantago major

“…aqueous matrix of the cell wall) yield a suite of potentially damaging reactive oxygen species (ROS) which, in sufficient concentrations, can breach the extracellular defence systems and cause oxidative damage to the plasmalemma, resulting, ultimately, in cell death (Heath, 1987(Heath, , 1994Heath & Taylor, 1997). At the physiological level, the oxidative stress induced by O $ is reflected in a decline in the photosynthetic capacity of individual leaves (Pell, Eckardt & Glick, 1994 ;Farage & Long, 1995), increased rates of maintenance respiration (Amthor, 1988), relatively greater retention of fixed carbon in leaves (Balaguer et al, 1995) and accelerated rates of leaf senescence (Ting & Mukherjee, 1971 ;Nie, Tomasevic & Baker, 1993) resulting in reduced growth and productivity. There is, however, evidence that plants can ' acclimate ' to O $ .…”

Senescence-Associated Gene Expression during Ozone-Induced Leaf Senescence in Arabidopsis1

“…O 3 exposure accelerates chlorophyll and protein loss and reduces photosynthetic capacity and efficiency in older leaves (Reich, 1983;Held et al, 1991;Nie et al, 1993). Accelerated loss of Rubisco protein is also closely associated with O 3 -induced senescence (Pell and Pearson, 1983;Nie et al, 1993;Pell et al, 1997). O 3 exposure reduced transcript levels for cab, rbcS, and rbcL (large subunit of Rubisco) in potato (Glick et al, 1995) and cab and rbcS in Arabidopsis (Conklin and Last, 1995) and tobacco (Bahl and Kahl, 1995).…”

“…Ozone (O 3 ) is a stress known to induce accelerated foliar senescence in many plant species including potato, radish, alfalfa, wheat, and hybrid poplar (Pell and Pearson, 1983;Reich, 1983;Held et al, 1991;Nie et al, 1993;Pell et al, 1997). O 3 exposure accelerates chlorophyll and protein loss and reduces photosynthetic capacity and efficiency in older leaves (Reich, 1983;Held et al, 1991;Nie et al, 1993).…”

The Effect of Leaf-Level Spatial Variability in Photosynthetic Capacity on Biochemical Parameter Estimates Using the Farquhar Model: A Theoretical Analysis

“…Effects of ozone are known to be heterogeneous across the leaf surface, (Nie et al, 1993), suggesting that decrease in V c,max relative to decrease in J max would not be uniform across the leaf. Senescence within a leaf is often patchy and, because Rubisco protein is catabolized before the membrane proteins of the electron transport apparatus (Weng et al, 2005), uncoupled variation in V c,max and J max could result during the latter part of a leaf's lifespan.…”