High salt stress in wheat leaves causes retardation of chlorophyll accumulation due to a limited rate of protochlorophyllide formation

Abstract

When exposed to salt stress, leaves from dark‐grown wheat seedlings (Triticum aestivum, cv. Giza 168) showed reduced accumulation of chlorophyll during irradiation. To elucidate the mechanism behind salt‐influenced reduction of chlorophyll biosynthesis, we have investigated the effect of salt stress on the spectral forms of Pchlide, the phototransformation of Pchlide to Chlide, the Shibata shift, the regeneration of Pchlide and the accumulation of Pchlide from 5‐aminolevulinic acid (ALA). We found that the phototransformation of Pchlide to Chlide was not affected by salt stress. The blue shift (Shibata shift) of newly formed Chlide was delayed both after flash irradiation and in continuous light. The reformation of Pchlide in darkness after a flash irradiation or after a period of 3‐h irradiation was retarded in the salt‐treated leaves. However, after a 20‐h dark period, Pchlide was reformed even in salt‐treated leaves but the formation of short‐wavelength Pchlide was suppressed. Compared to controls, salt treatment also reduced the amount of Pchlide accumulated in leaves floated on ALA. The increase in the low temperature fluorescence emission spectrum at 735 nm, which occurred gradually during several hours of irradiation with continuous light in control leaves, was completely suppressed in salt‐treated leaves. It is concluded that salt stress inhibits chlorophyll accumulation partly by reducing the rate of porphyrin formation but, as discussed, also by a possible reduction in the formation of chlorophyll‐binding proteins.

Interactions between Pseudomonas putida UW4 and Gigaspora rosea BEG9 and their consequences for the growth of cucumber under salt-stress conditions

“…Concerning photosynthetic efficiency, the measurements were taken on the second leaf in order of appearance; this was one of the oldest leaves of the plants and subjected to both the salt stress and the effect of the micro-organisms for a relatively long time compared to the younger leaves. In agreement with other reports (Stepien and Klobus 2006;Abdelkader et al 2007), the photosynthetic efficiency of salt-stressed plants, evaluated as PI, was five times lower than that recorded in control plants.…”

Modulation of chlorophyll biosynthesis by water stress in rice seedlings during chloroplast biogenesis*

“…2000, 2001). In the same vein, arrest of Shibata shift was demonstrated in heat‐stressed (Mohanty & Tripathy 2011) and salt‐stressed (Abdelkader, Aronsson & Sundqvist 2007) wheat seedlings. On the contrary, in chill stress, the Shibata shift was partially affected (Mohanty & Tripathy 2011).…”

Prolonged salt stress alters the ratios of protochlorophyllide spectral forms in dark-grown wheat (Triticum aestivum) and influences chlorophyll a accumulation following irradiation

“…3a) and the susceptible cultivar (Abdelkader et al 2007). During flash irradiation, Pchlide is transformed to Chlide and the peak at 655 nm is replaced with a peak at 685 nm, representing the newly formed Chlide.…”