Aluminum-Induced Changes in Cell-Wall Glycoproteins in the Root Tips of Al-Tolerant and Al-Sensitive Wheat Lines

To investigate wheat (Triticum aestivumL.) responses to Al stress, KCl- and SDS-extracted glycoproteins (covalently bound proteins isolated by cell-wall digestion by cellulysine–pectolase mixture) and extensins (hydroxyproline-containing glycoproteins, HRGPs) were isolated from cell-wall preparations purified from the root apices of Al-sensitive and Al-tolerant near-isogenic lines ES8 and ET8. Under Al stress conditions, two lines differed mostly in their extensins. The untreated plants of two lines were low in covalently bound extensins, although the content of this protein fraction in ES8 was higher than in ET8. When the seedlings were treated with Al, the extensin content increased in both wheat lines and especially in the Al-tolerant ET8 plants. Using two-dimensional electrophoresis, the authors demonstrated the accumulation of polypeptides with mol wts of 22.2 kD (pI 5.5–6.5), 24.5 kD (pI 5.8–6.0), and 33.1 kD (pI 5.25) and polypeptides of 22.2 kD (pI 6.8–7.6) and 40.5 kD (pI 7.6) in the extensin fraction from the cell walls of the Al-sensitive plants. The regulation of cell responses to Al stress may involve extensin expression.     

Detection of lymphocytes binding erythrocytes conjugated with Salmonella antigens

Immune reagents for the detection of specific antigen-binding lymphocytes (ABL) with respect to different Salmonells antigens were developed. Rabbits were immunized with killed S. typhi and other salmonellae containing cross-reacting antigens, and the dynamics of the formation of ASL of each specificity was studied. Differences in the time of the appearance of ASL with receptors to thymus-independent (09, 12 or Vi) and thymus-dependent (Hd) antigens were studied. The relative content of ASL, determined with the use of immune reagents prepared from S. typhi antigens, was higher, on the whole, in rabbits immunized with S. typhi than in rabbits immunized with salmonellae containing one of cross-reacting antigens (S. enteritidis--09, 12; S. paratyphi C--Vi; S. virginia--Hd).     

Adaptation potential of photosynthesis in wheat cultivars with a capability of leaf rolling under high temperature conditions

For the first time, the adaptive role of the rolling leaf trait for tolerance of wheat plants (Triticum aestivum L.) to the main factor of drought, high temperature, was demonstrated. Cv. Otan with high degree of this trait expression was more tolerant to temperature stress (40°C, 4 h during 2 days (2h/day)). Changes in parameters of chlorophyll fluorescence, F _v/F _m and R _Fd690, suggest that cv. Otan was tolerant to inhibition of photochemical activities of photosystem II (PSII) and photosystem I (PSI). Furthermore, high temperature had no effect on the rate of net photosynthesis (P _N) in cv. Otan, although it decreased this parameter in the other wheat cultivars. The main factors, which provid for this tolerance, were adaptation of the photosynthetic pigment system by active accumulation of carotenoids, more stable structural organization of PSII and PSI, and their high photosynthetic activities, as well as efficient stomatal regulation of transpiration and supplying of mesophyll cells with CO₂. It is hypothesized that the physiological role of the rolling leaf trait is the maintenance of adaptation potential by increasing the efficiency of water metabolism in the flag leaves of wheat under high temperature.