We measured energy substrates in haemolymph and flight muscles of the large blister beetle Mylabris oculata at rest and after tethered, lift-generating flight. Flight of 1 min duration at an ambient temperature of 38-42°C did not effect a change in the concentration of lipids in the haemolymph, whereas a small, significant decrease in the concentrations of carbohydrates and a 3-fold larger one in the levels of proline were noted, as well as a concomitant increase in alanine. In the flight muscles, glycogen and proline concentrations were diminished slightly but significantly upon flight, whereas alanine levels were increased. Two hours of rest after a flight of 1 min completely reversed the metabolic situation in haemolymph and flight muscles to pre-flight levels. We could isolate two neuropeptides from the corpora cardiaca of M. oculata, which by retention time and mass analyses are characterised as the decapeptide Del-CC (pGlu-Leu-Asn-Phe-Ser-Pro-Asn-Trp-Gly-Asn-NH2) and the octapeptide Tem-HrTH (pGlu-Leu-Asn-PheSer-Pro-Asn-Trp-NH2) previously fully identified from the corpora cardiaca of the blister beetle, Decapotoma lunata (Gäde, 1995). Subsequently, it was unequivocally demonstrated that low doses of Del-CC and Tem-HrTH elicited increases in the concentration of proline and carbohydrates in the haemolymph of D. lunata and M. oculata, but did not change the concentration of lipids in both species. In conclusion, the two endogenous peptides are hypertrehalosaemic and hyperprolinaemic, thus very likely regulating the mobilisation of the two important flight substrates of blister beetles, namely carbohydrates and proline., Gerd Gäde, Lutz Auerswald, and Lit
Predicted future climatic changes for the Mediterranean region give additional importance to the study of photooxidative stress in local economic species subjected to combined drought and
high-temperature conditions. Under this context, the impact of these stresses on photosynthesis, energy partitioning, and membrane lipids, as well as the potential ability to attenuate oxidative damage, were investigated in Ceratonia siliqua L. Two thermal regimes (LT: 25/18°C; HT: 32/21°C) and three soil water conditions (control, water stress, and rewetting) were considered. HT exacerbated the adverse effects of water shortage on photosynthetic rates (PN) and PSII function. The decrease in PN was 33% at LT whereas at HT it was 84%. In spite of this, the electron transport rate (ETR) was not affected, which points to an increased allocation of reductants to sinks other than CO2 assimilation. Under LT conditions, water stress had no significant effects on yield of PSII photochemistry (ΦPSII) and yields of regulated (ΦNPQ) and nonregulated (ΦNO) energy dissipation. Conversely, drought induced a significant decrease of ΦPSII and a concomitant increase of ΦNO in HT plants, thereby favouring the overproduction of reactive oxygen species (ROS). Moreover, signs of lipid peroxidation damage were detected in HT plants, in which drought caused an increase of 40% in malondialdehyde (MDA) content. Concurrently, a marked increase in proline content was observed, while the activities of catalase (CAT) and ascorbate peroxidase (APX) were unaffected. Despite the generation of a moderate oxidative stress response, C. siliqua revealed a great capability for photosynthetic recovery 36 h after rewatering, which suggests that the species can cope with predicted climate change. and M. L. Osório ... [et al.].
Morpho-physiological and biochemical analyses were carried out in eight diverse indigenous muskmelon (Cucumis melo L.) genotypes exposed to different degrees of water deficit (WD). The ability of genotypes MM-7, and especially MM-6, to counteract better the negative effect of WD was associated with maintaining higher relative water content (RWC), photosynthetic rate, efficiency of PSII, and photosynthetic pigments compare to other genotypes. Furthermore, MM-6 showed a better ability to maintain cellular homeostasis than the others. It was indicated by a stimulated antioxidative defense system, i.e., higher activities of antioxidant enzymes, accumulation of nonenzymatic antioxidants together with lower concentration of reactive oxygen species and malondialdehyde. However, the genotypes MM-2 and MM-5 suffered greatly due to WD and showed reduced RWC, photosynthetic rates, pigment content, and exhibited higher oxidative stress observed as lower antioxidant enzyme activities., W. A. Ansari, N. Atri, B. Singh, P. Kumar, S. Pandey., and Obsahuje bibliografii
Our experiment was conducted in order to find out effects of paclobutrazol (PBZ; 30 μl l-1) on morphology, photosynthetic process, and stress markers under water surplus and deficit conditions in several wheat genotypes. Study revealed that relative water content (RWC), photosynthetic rate, and maximal quantum yield of PSII (FV/FM) was improved after a PBZ application both under irrigation and water deficit across the genotypes, while the stomatal conductance was reduced. Further, the application of PBZ led to reduced leaf area in wheat genotypes. Moreover, a proline content was higher in the wheat genotypes under water stress as compared to the irrigated plants. The application of PBZ led to downregulation of the proline content under water deficit, while there was no significant change in the content and activity under irrigation with or without the PBZ treatment. These findings indicated that due to the application of PBZ the wheat genotypes might sense a lower stress level (indicated by the proline content) and better drought tolerance (according to RWC and photosynthetic characteristics)., S. K. Dwivedi, Ajay Arora, S. Kumar., and Obsahuje bibliografii
Salinised (150 mM NaCl for 15 d) roots excised from salt sensitive wheat cultivar Giza 163 showed about 15-fold increase in the ratio of Na/K while salt tolerant Sakha 92 exhibited only 7.5-fold increase compared to their control ratios. Root ratio of saturated/unsaturated fatty acids was stimulated twice in the sensitive cultivar versus 1.7-fold increase in the tolerant ones. Salinity enhanced greatly the accumulation of spermine (Spm) and spermidine (Spd) contents associated with a decrease in putrescine (Put) content in both wheat cultivars. Higher ratios of Spm+Spd/Put associated with lower content of proline and low ethylene evolution were detected in shoots and roots of salt tolerant cultivar. Chlorophyll a/b ratio showed an increase from 1.3 in control of both cultivars to 1.6 and 1.4 in stressed Giza 163 and Sakha 92, respectively. A reduced Hill reaction activity (19 %) was observed in stressed chloroplasts isolated from leaves of the tolerant cultivar versus 40 % inhibition in the sensitive ones. Moreover, chloroplasts isolated from stressed leaves of the sensitive cultivar showed about 25 % reduction in fluorescence emission at 685 nm as well as shifts in the peaks in the visible region.
In a glasshouse, Bemisia tabaci infestation largely reduced response of photosynthesis to irradiance and CO2 concentration of Mikania micrantha compared with the non-infested control (C) ones. The maximum irradiance-saturated photosynthetic rate
(Pmax) and saturation irradiance (SI) of the infested M. micrantha were only 21.3 % and 6.5 % of the C-plants, respectively. B. tabaci infestation led to the reduction of contents of chlorophyll and carotenoids in M. micrantha, which was accompanied with the decrease of actual photosystem 2 (PS2) efficiency (ΦPS2), efficiency of excitation energy capture by open PS2 reaction centres (Fv'/Fm'), electron transport rate (ETR), and photochemical quenching (qP). Moreover, superoxide dismutase and catalase activities significantly decreased while proline and glutathione contents significantly increased in infested M. micrantha. Hence B. tabaci infestation not only induced direct damage of photosynthetic apparatus but also altered the antioxidant enzymes activities in M. micrantha, which might as consequences accelerate senescence of this weed. and L. L. Zhang, D. Z. Wen.
In view of predicted climatic changes for the Mediterranean region, study of high temperature and drought impacts on physiological responses of endangered species regains relevance. In this context, micropropagated plants of Tuberaria major, a critically endangered species, endemic of Algarve, were transferred to a controlled-environment cabinet with day/night temperatures set at 25/18°C (Reference) or 32/21°C (HT). After 15 days of HT acclimation, some plants were subjected to progressive drought followed by rewatering. The enhancement of temperature alone did not affect water relations and photosynthetic rates (PN) but the stomatal conductance (gs) exhibited a 3-fold increase in comparison with reference plants. The maximum quantum yield of photosystem (PS) II (Fv/Fm), the effective quantum yield of PSII photochemistry (ΦPSII), carotenoid (Car) and anthocyanin content enhanced, whereas the quantum yields of regulated (ΦNPQ) and nonregulated (ΦNO) energy dissipation decreased. Drought combined with HT reduced predawn leaf water potential to values of about -1.3 MPa, which had adverse effects on gas exchange and PSII activity. Values of PN and gs were 71 and 79% lower than those of HT plants. An impairment of photochemical activity was also observed: the decrease in ΦPSII and the increase of ΦNPQ. However, an irreversible photoinhibitory damage had not occurred. Carotenoid and anthocyanin content remained elevated and soluble sugars (SS) increased twice, whereas proline and MDA accumulation was not detected. On the first 24 h after water-stress relief, gs, PN, ΦPSII, and ΦNPQ did not recover, but SS returned to the reference level. Overall, T. major acquired an adequate capacity for a protection against the development of oxidative stress during drought and water recovery under HT. These findings suggest that T. major is prepared to deal with predicted climate changes., M. L. Osório, J. Osório, A. Romano., and Obsahuje bibliografii
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.
Gas exchange, chlorophyll (Chl) fluorescence, and contents of some metabolites in two genotypes of jasmine (Jasminum sambac), single petal (SP) and double petal (DP) one, were analyzed during dehydration and re-hydration. Water stress significantly decreased net photosynthetic rate, stomatal conductance, and maximum photochemical efficiency (Fv/Fm) in both jasmine genotypes, but increased minimum fluorescence (F0) only in DP-jasmine. Water stress also decreased starch content, while increased contents of total soluble sugars and proline in leaves of both genotypes. SP-jasmine demonstrated higher drought tolerance as evidenced by maintaining higher gas exchange and photochemical efficiency and lower alteration of metabolites than DP-jasmine. Recovery analysis revealed that drought-induced injury in photosynthetic machinery in jasmine plants was reversible. DP-jasmine exhibited a slow recovery of drought-induced impairment in photosynthetic activity and associated metabolites, suggesting that this genotype had lower capacity to adapt to water limited condition. Higher yield stability of SP-than that of DP-jasmine under rain-fed condition finally confirmed higher drought tolerance of SP-jasmine. and H. Cai ... [et al.].
We examined the physiological and biochemical responses of two halophytic grasses with different photosynthetic pathways, Puccinellia tenuiflora (C3) and Chloris virgata (C4), to saline-alkaline stresses. Plants were grown at different Na2CO3 concentrations (from 0 to 200 mM). Low Na2CO3 (< 12.5 mM) enhanced seed germination and plant growth, whereas high Na2CO3 concentrations (> 100 mM) reduced seed germination by 45% in P. tenuiflora and by 30% in C. virgata. Compared to C. virgata, P. tenuiflora showed lower net photosynthesis, stomatal conductance, intercellular CO2 concentration, and water-use efficiency under the same treatment. C. virgata exhibited also relatively higher ATP content, K+ concentration, and the K+/Na+ ratio under the stress treatments implying that salt tolerance may be the main mechanism for salt resistance in this species. Our results demonstrated that the C. virgata was relatively more resistant to saline-alkaline stress than the co-occurring P. tenuiflora; both two species adapt to their native saline-alkaline habitat by different physiological mechanisms., C. Y. Guo, X. Z. Wang, L. Chen, L. N. Ma, R. Z. Wang., and Obsahuje bibliografii