N. Nedunchezhian

Low night temperature effects on photosynthetic performance on two grapevine genotypes

The functional activities of the photosynthetic apparatus of two grapevine genotypes (Vitis vinifera L. cvs. Müller-Thurgau and Lagrein) were investigated after low night temperature (LNT) treatment for 7 d. LNT caused important reductions of the net photosynthetic rate (PN) of Lagrein plants due to non-stomatal components. These non-stomatal effects were not evident in Müller-Thurgau. At LNT treatment, the contents of photosynthetic pigments decreased significantly in Lagrein, but in Müller-Thurgau the contents of chlorophyll (Chl) remained unchanged whereas the contents of carotenoids (Car) increased. An increase and decrease of Chl a/b was shown in Mü ller-Thurgau and Lagrein stressed plants, respectively. RuBPC activity and content of soluble proteins were also significantly reduced in Lagrein. Under LNT treatment, photosystem (PS) 2 was markedly more inhibited in Lagrein than in Müller-Thurgau. The decrease in PS 2 activity in Lagrein was mostly due to the marked loss of D1, 47, 43, 33, 28-25, 23 and 17 kDa proteins determined by immunological and SDS-PAGE studies.

Changes induced by ultraviolet-B (280-320 nm) radiation to vegetative growth and photosynthetic characteristics in field grown Vigna unguiculata L.

Abstract The effect of ultraviolet-B (280–320 nm) radiation on growth and photosynthetic characteristics were investigated in field grown Vigna unguiculata L. Plants were grown at ambient and ambient plus a 1.8 kJ/m 2 supplementation of UV-B radiation for 25 days. The supplemental UV-B fluence used in this experiment simulated a 16% depletion in stratospheric ozone at midday in the summer at 10N latitude. Exposure to UV-B radiation had increased the plant height, leaf area and leaf biomass. The level of total chlorophyll on a unit fresh weight basis showed marginally decreased in the UV-B treated seedlings. No significant difference was seen in the concentration of UV-B absorbing compounds and RuBP case activity in UV-B treated seedlings. However, when various photosynthetic activities were followed in isolated chloroplasts, UV-B enhanced radiation stimulated the whole chain, photosystem (PS) I and PS II activity during the first 5 days. Prolonged treatment under UV-B enhanced radiation caused inhibition of the whole chain and the PS II activity. The artificial electron donor, Mn 2+ failed to restore UV-B radiation induced loss of PS II activity, while DPC and NH 2 OH partially restored the PS II activity.

Effect of water deficit on photosynthetic and other physiological responses in grapevine (Vitis vinifera L. cv. Riesling) plants

The grapevine (Vitis vinifera L. cv. Riesling) plants subjected to water deficit were studied for changes in relative water content (RWC), leaf dry mass, contents of chlorophyll (Chl), total leaf proteins, free amino acids, and proline, and activities of ribulose-1,5-bisphosphate carboxylase (RuBPC), nitrate reductase (NR), and protease. In water-stressed plants RWC, leaf dry matter, Chl content, net photosynthetic rate (PN), and RuBPC and NR activities were significantly decreased. The total leaf protein content also declined with increase in the accumulation of free amino acids. Concurrently, the protease activity in the tissues was also increased. A significant two-fold increase in proline content was recorded.

Shade effect alters leaf pigments and photosynthetic responses in Norway spruce (Picea abies L.) grown under field conditions

The contents of chlorophyll (Chl) and carotenoids (Car) per fresh mass were lower in shade needles than in sun needles. Ribulose-1,5-bisphosphate carboxylase (RuBPC) activity and contents of soluble proteins were also significantly lower in shade needles. In isolated thylakoids, a marked lower rate of whole chain and photosystem (PS) 2 activities were observed in shade needles. Smaller lower rate of PS1 activity was also observed in shade needles. The artificial exogenous electron donors, diphenyl carbazide (DPC) and NH2OH, significantly restored the loss of PS2 activity in shade needles. Similar results were obtained when Fv/Fm was evaluated by Chl fluorescence measurements. The marked lower rate of PS2 activity in shade needles was due to the lower contents of 47, 33, 28–25, 23, and 17 kDa polypeptides. This conclusion was confirmed by immunological studies showing that the content of the 33 kDa protein of the watersplitting complex was diminished significantly in shade needles.

Effects of Phytoplasma Infection on Pigments, Chlorophyll-Protein Complex and Photosynthetic Activities in Field Grown Apple Leaves

Changes in contents of pigments, chlorophyll-protein complex, and photosynthetic activities were investigated in field grown apple (Malus pumila Mill.) leaves infected by Apple Proliferation phytoplasma. The contents of chlorophyll a+b (Chl) and carotenoids (Car) markedly decreased in infected leaves. Similar results were also observed for content of total soluble proteins and ribulose-1,5-bisphosphate carboxylase activity. When various photosynthetic activities were followed in isolated thylakoids, phytoplasma infection caused a marked inhibition of whole chain and photosystem 2 (PS2) activity. Smaller inhibition of photosystem 1 (PS1) activity was observed even in severely infected leaves. The artificial exogenous electron donors, MnCl2 diphenyl carbazide, and NH2OH, did not restore the loss of PS2 activity in both mildly and severely infected leaves. Similar results were obtained by Chl fluorescence measurements. The marked loss of PS2 activity in infected leaves was due to the reduction of contents of chlorophyll and light-harvesting chlorophyll-protein 2 complexes.

Iron deficiency induced changes on the donor side of PS II in field grown grapevine (Vitis vinifera L. cv. Pinot noir) leaves

Abstract In this work we have studied the influence of lime-induced iron deficiency on some features of the thylakoids and PS II membranes from grapevine ( Vitis vinifera L. cv. Pinot noir) plants grown in calcareous soils. Changes in photosynthetic activities and PS II membrane polypeptides were investigated. When various photosynthetic electron transport activities were analyzed in isolated thylakoids, a major decrease in the rate of whole chain (H 2 O→MV) electron transport was observed in chlorotic leaves. Such reduction was mainly due to the loss of PS II activity. Smaller inhibition of PS I activity was also observed in chlorotic leaves. The artificial electron donors, DPC and NH 2 OH markedly restored the loss of PS II activity in chlorotic leaves. The same results were obtained when variable fluorescence/maximum fluorescence (Fv/Fm) was evaluated by chlorophyll (Chl) fluorescence measurements. The marked loss of PS II activity in chlorotic leaves was evidently due to the loss of D1, 33, 28–25, and 23 kDa polypeptides. This conclusion was confirmed by immunological studies showing that the content of the D1 protein of the PS II reaction centre and of the 33 kDa protein of the water-splitting complex was diminished significantly in chlorotic leaves.

Triacontanol can protect Erythrina variegata from cadmium toxicity

Summary The simultaneous effect of 0, 10, 100 and 1000 μmol/L Cd 2+ [Cd(NO 3 ) 2 × 4H 2 O] and 1 mg kg −1 (H 2 O) triacontanol [TRIA] spray on certain parameters of growth, pigments, starch, 14 CO 2 fixation, ribulose-1,5-bisphosphate carboxylase (Rubisco), nitrate reductase (NR) and photosynthesis in Erythrina variegata seedlings was studied. With increasing Cd 2+ concentration in the nutrient solution the monitored activities decreased. When the seedlings were subsequently sprayed with triacontanol the cadmium effect was partially or completely reversed indicating that TRIA can protect from cadmium toxicity.

Effects of ultraviolet-B enhanced radiation and temperature on growth and photochemical activities inVigna unguiculata

Changes in growth characteristics and photochemical activities inVigna unguiculata L. Walp seedlings maintained at constant temperature of 10, 20, 30 and 40 ‡C under control and ultraviolet-B enhanced radiation (UV-B) were investigated. UV-B retarded the shoot elongation and also leaf expansion to a great extent at 30 ‡C but produced only marginal changes at 20 and 40 ‡C. Similar response was also observed with respect to changes in leaf fresh and dry masses and total chlorophyll (Chl) content under these temperatures. At 10 ‡C the total Chl content was 3-fold higher under the treatment than under control conditions. In seedlings growing at 20 and 30 ‡C the overall photosynthetic electron transport (H2O -> methyl viologen) showed a significant enhancement during the 36-h UV-B treatment and thereafter a gradual reduction. Although a similar trend was found in photosystem 1 (PS1), the inhibition even after 60 h of UV-B treatment was not statistically significant. Photosystem 2 (PS2) activity was inhibited in seedlings treated for 60 h by UV-B at 20 and 30 ‡C. However, no inhibition was observed at 40 ‡C. No detectable photochemical activity was found in seedlings grown at 10 ‡C under either control or UV-B enhanced irradiation although the chloroplasts contained Chl.

Photoinhibition of Photosynthesis in Sun and Shade Grown Leaves of Grapevine (Vitis vinifera L.)

The degree of photoinhibition of sun and shade grown leaves of grapevine was determined by means of the ratio of variable to maximum chlorophyll (Chl) fluorescence (Fv/Fm) and electron transport measurements. The potential efficiency of photosystem 2 (PS2), Fv/Fm, markedly declined under high irradiance (HI) in shade leaves with less than 10 % of F0 level. In contrast, Fv/Fm ratio declined with about 20 % increase of F0 level in sun leaves. In isolated thylakoids, the rate of whole chain and PS2 activity in HI shade and sun leaves was decreased by about 60 and 40 %, respectively. A smaller inhibition of photosystem 1 (PS1) activity was also observed in both leaf types. In the subsequent dark incubation, fast recovery was observed in both leaf types that reached maximum PS2 efficiencies similar to non-photoinhibited control leaves. The artificial exogenous electron donors DPC, NH2OH, and Mn2+ failed to restore the HI-induced loss of PS2 activity in sun leaves, while DPC and NH2OH were significantly restored in shade leaves. Hence HI in shade leaves inactivates on the donor side of PS2 whereas it does at the acceptor side in sun leaves, respectively. Quantification of the PS2 reaction centre protein D1 and the 33 kDa protein of water splitting complex following HI-treatment of leaves showed pronounced differences between shade and sun leaves. The marked loss of PS2 activity in HI leaves was due to the marked loss of D1 protein of the PS2 reaction centre protein and the 33 kDa protein of the water splitting complex in sun and shade leaves, respectively.

Ameliorating effect of triacontanol on acidic mist-treated Erythrina variegata seedlings: Changes in growth and photosynthetic activities

Abstract In seedlings of the tropical tree species Erythrina variegata Lam. exposed to different acidic mist (H 2 SO 4 , pH 5.6, 4.0 and 2.0) for 7 days significant reduction in seedling growth (root and shoot length, leaf density, leaf area, fresh and dry mass accumulation) and photosynthetic activities were determined. In isolated thylakoid, a decrease in the activity of PS II and whole chain electron transport was observed at pH 4.0 and 2.0, but no significant transport was observed in PS I activity. When the seedlings were subsequently sprayed with TRIA, the acidic mist effect was partially or completely reversed indicating that TRIA can protect from acidic mist treatment. The artificial electron donors DPC and NH 2 OH markedly restored to the loss of PS II activity in acidic mist-treated leaves (pH 2.0). We believe that this is the first report of alleviating the acidic mists by TRIA.