Light and electron microscopy were used to relate histological and ultrastructural differences of barley leaves treated with different concentrations of salicylic acid (SA, 100 µM-1 mM). Light microscopy revealed that the thickness of all leaf tissue components decreased in SA-treated plants. The effect was most pronounced on the width of the adaxial epidermis and on the size of the bulliform cells. The chloroplast ultrastructure was also affected by SA treatment. Swelling of grana thylakoids in various degrees, coagulation of the stroma, and increase in chloroplast volume were observed. 1 mM SA caused a vast destruction of the whole plastid structure. and A. N. Uzunova, L. P. Popova.
72 to 120 h of soil flooding of barley plants (Hordeum vulgare L. cv. Alfa) led to a noticeable decrease in the rates of CO2 assimilation and transpiration, and in chlorophyll and dry mass contents. Stomatal conductance decreased following flooding without appreciable changes in the values of intercellular CO2 concentrations. A drop in the activity of ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) and of the photorespiratory enzymes phosphoglycollate phosphatase (EC 3.1.3.18) and glycollate oxidase (EC 1.1.3.1) was observed, while the activity of phosphoenolpyruvate carboxylase (EC 4.1.1.31) increased in all flooded plants. Flooding of barley plants caused an increase in proline content and in leaf acidity. and R. Y. Yordanova, L. P. Popova.
Short-term (2 h) treatment with 10 µM abscisic acid decreased stomatal conductance and net photosynthetic rate, and increased carbonic anhydrase activity in pea seedlings. The treatment with 10 µM methyl jasmonate did not significantly affect these parameters. and G. N. Lazova, M. I. Kicheva, L. P. Popova.
Twelve-day-old barley seedlings were supplied with 23 μM methyl jasmonate (MeJA) or 10 μM paraquat (Pq) via the transpiration stream and kept in the dark for 24 h. Then they were exposed to 100 μmol m-2 s-1 PAR and samples were taken 1, 2, 3, and 6 h after irradiation. Treatment of seedlings with MeJA alone resulted in decreased content of chlorophyll (Chl), and net photosynthetic (PN) and transpiration rates. Pq treatment led to a decrease in Chl content and to a very strong inhibition of PN, the effects were manifested by 1 h of irradiation. Pq treatment did not affect the activity of ribulose-1,5 bisphosphate carboxylase (RuBPC, EC 4.1.1.39) but increased the activity of the photorespiratory enzymes phosphoglycolate phosphatase (PGP, EC 3.1.3.18), glycolate oxidase (GO, EC 1.1.3.1), and catalase (EC 1.11.1.6). Pre-treatment of seedlings with MeJA before exposure to Pq fully blocked the inhibitory effect of Pq on photosynthesis and protected against subsequent Pq-induced oxidative damage. and V. A. Hristova, L. P. Popova.