Environmental Benefits Of Wheat (PSI)

Wheat (Triticum aestivum L.) is one of the most important agricultural crops as it is one of the four major cereals in the world. wheat is a staple food crop for a large portion of the world’s population (Zhang et al., 2012) It is grown under both rain-fed and irrigated cultivation and thus under conditions subjected to many environmental stresses (Tardif et al., 2007). Unfortunately, its production is severely affected by adverse environmental stresses. Stress can be defined as an adverse force or a condition, which inhibits the normal functions of a biological system such as plants (Levitt, 1980; Jones and Jones, 1989). Stresses are divided into biotic and abiotic stresses, Abiotic stresses such as drought, high salinity and heat which

PSI is consists of at least 8 polypeptides which responsible for NADP+ reduction and cyclic photophosphorylation . Its major components are the P700 chlorophyll a A1 and A2 apoproteins whose molecular weights vary between 60 and 70 kd, depending on the species (Jensen P.E, et al., 2007).
The PSI complex of most plants and algae consists of 13 subunits: at least five chloroplast encoded subunits (PsaA, PsaB, PsaC, PsaI and PsaJ) and eight nucleus encoded subunits (PsaD,PsaE, PsaF, PsaG, PsaH, PsaK, PsaL, PsaN) and numerous redox cofactors and antenna chlorophyll (Ihnatowicz et al.,2004). PSI is a monomer in plants (Scheller et al., 2001; Ben-Shem et al., 2003) and a trimer in cyanobacteria (Boekema et al., 1987; Fromme and Witt, 1998) with two membrane complexes as the reaction centre (RC) core and the outer light harvesting complex (LHC) .According to Nelson and Yocum (2006) the photochemical quantum yield of PSI is close to 1.0. For this reason, PSI is considered as the most efficient light capturing and energy converting device in nature (Amunts and Nelson, 2009). Amunts and Nelson (2009) identified that a PSI-LHCI super complex consists of 13 proteins, where four of them are the peripheral LHC proteins (Lhca1,Lhca2, Lhca3, Lhca4), 45 transmembrane helices, 3 stroma-exposed subunits, 1 lumenal subunit,168 chlorophylls. Apart from that, 3 Fe4-S4 clusters, 2

Salt has a major impact on photosynthetic pigments, such as chlorophylls and carotenoids in leaves and this causes leaf chlorosis and senescence (Hernandez et al., 1995; Hernandez et al., 1999; Gadallah, 1999; Agastian et al., 2000). Work from Kennedy and DeFillippis (1999) pointed out that, compared to chlorophyll-a and carotenoids, the decline of protochlorophylls and chlorophyll-b is greater with increasing salt. Another study on pigment composition in tomato showed that salt affects the total chlorophyll and carotene content in leaves (Khavari-Nejad and Mostofi, 1998). Studies have shown a change in the protein and lipid composition of plants under salt stress. Another Work showed that leaf protein content decreased with increasing salt in Bruguiera parviflora (Parida et al., 2002) . A study by Hassanein (1999) pointed out that peanut (Arachis hypogaea L.) exposed to high NaCl concentration showed an increase in certain polypeptides (127 and 57 kDa) and a decrease in others (260 and 38 kDa). Lipids are important as they act as an efficient energy store, hormones and as a part of the cellular membranes (Singh et al., 2002). The phospholipid bilayers are involved in mechanisms of desiccation tolerance in plants. Sugars like trehalose help to stabilize the lipid bilayers under water deficit conditions (Singh et al.,