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Get Support. Feedback Please let us know what you think of our products and services. Give Feedback. Get Information. Open Access Article. Umme Aktari Nadira. Cheng-Wei Qiu. Fangbin Cao. Guoping Zhang. Paul Holford. Feibo Wu. Dayton right middleTadmor right panel grown under pH 6. Tibetan wild barley had increased GSH concentrations and showedless damage to chloroplasts, mitochondria, and DNA after treatment with pH 4.
The dotted arrow indicates spontaneous conversion. Arrows indicate the potential connections and dotted arrow indicates spontaneous conversion. Aluminum Al toxicity and drought are two major constraints on plant growth in acidic soils, negatively affecting crop performance and yield. Moreover, XZ5 and XZ29 possessed increased levels in reduced ascorbate and glutathione under these conditions, and antioxidant enzyme activities were largely stimulated by exposure to pH 4.
Microscopic imaging of each genotype revealed DNA damage and obvious ultrastructural alterations in leaf cells treated with drought or Al alone, and combined pH 4. Collectively, the authors findings indicated that the higher tolerance of the wild barley to combined pH 4. Variations in rainfall distribution and longer dry spells due to global climate change in much of the tropics during the main growing period of crops are increasingly becoming important yield-limiting factors.
As a result, crop genotypes tolerant to both drought and Al toxicity need to be developed. Therefore, a combination of research approaches is urgently needed in order to understand the nature of multiple stress responses and to create avenues for developing plants that are resistant to multiple stresses yet maintain high yields [ 3 ].
The primary effect of Al toxicity is a reduction in root growth, which can severely affect water and nutrient uptake, Fat women looking to fuck in GrAbove A reducing crop yield [ 45 ]. It has been reported that Al toxicity produces disturbances in peripheral tissues in root and root thickening of Vaccinium corymbosum [ 6 ].
Little information has been reported on the effects of Al on shoots. However, Konarska [ 7 ] showed that Al exposure reduced the size and thickness of leaf blades, due to a decrease in cell size, as well as an increase in stomata in the abaxial epidermis, with a simultaneous reduction in their size. These effects were accompanied by a decrease of photosynthetic pigment levels and photosynthetic parameters. Similarly, in cotton plants growing under Al toxicity, a reduction in leaf area and chlorophyll content was found [ 8 ].
Likewise, several reports indicate that Al also affects the photosynthetic performance by reducing stomatal conductance and the rate of electron transport [ 910 ]. In addition, Al induces an accumulation in reactive oxygen species ROSleading to oxidative stress in organelles and eventually in cell death [ 111213 ]. In low pH soils, chemical constraints and interactions among chemicals limit plant growth. For example, in low pH soils ranging from 4. Drought stress can cause several seriously deleterious effects on plant metabolic processes, including water relations, nutrient uptake and metabolism, and photosynthetic assimilation [ 15 ].
It was assumed that drought in an acidic Al-toxic soil would aggravate Al toxicity, which would further inhibit root growth and restrict water acquisition from the subsoil and the ability of plants to antagonize drought stress [ 16 ]. Studies have revealed that the physiological and biochemical responses of plants to the interaction of drought and salinity are unique and cannot be directly extrapolated from the responses to the two stresses individually [ 17 ].
However, little information is available regarding the combined stresses of Al and drought. Consequently, studies on Al and drought combined stresses are of great Fat women looking to fuck in GrAbove A ificance and are required to improve plant tolerance to the combined abiotic stress. Barley Hordeum vulgare L. Barley is also one of the most Al-sensitive species among cereals [ 19 ]. Acidic soil is distributed across 15 provinces in China, which covers an area of Therefore, it is important to identify genetic resources with a potential for tolerance to these different stresses, in order to breed tolerant barley cultivars.
Wild barley offers a great source of useful genes and genetic variation for crop improvement [ 20 ]. Annual wild barley from the Qinghai—Tibet Plateau is regarded as one of the progenitors of cultivated barley and is rich in genetic diversity [ 21 ]. However, the underlying physiological, biochemical, and cellular mechanisms involved in Al and Fat women looking to fuck in GrAbove A tolerance in the leaves remain unclear.
Therefore, changes in the leaf antioxidant defense system, oxidative injury, DNA damage, and cell ultrastructure under Al, low pH and simulated drought stress using polyethylene glycol PEG were investigated to study the Al and PEG tolerance mechanisms in Tibetan wild barley.
There was ificant phenotypic variation in response to pH, PEG-induced drought and Al stress Figure S1but the time of appearance and severity of stress symptoms differed among the genotypes. The effects of PEG and Al, both alone and in combination, on plant height, dry weight, and Al concentration of two barley cultivars are shown in Figure S2. Barley plants treated with low pH 4. PEG stress ificantly decreased plant height and dry weight relative to the control.
Plant height and dry weight of all four genotypes were further reduced due to the addition of Al compared to those at pH 4. Plants treated with pH 4. Only aluminum stress ificantly increased Al concentration in leaves of the four genotypes; Tadmor was the most affected. Remarkably, lower Al concentration in leaves was found when plants were exposed to pH 4.
The photosynthetic parameters of the four genotypes are shown in Figure S3. Barley plants exposed to low pH 4. The addition of PEG to the solution decreased all photosynthetic parameters compared to the control for all genotypes except for Ci in Tadmor in the pH 6.
Al stress dramatically decreased photosynthetic parameters in all genotypes compared to the control. The pH 4. In contrast, the activity of this enzyme was ificantly decreased in all genotypes under Al stress alone compared to those in the pH 4. For plants exposed to low pH 4. However, the addition of PEG and Al to the solution increased the activities of these enzymes compared to the control. When the plants were exposed to pH 4.
Low pH resulted in noticeable changes to the contents of these Fat women looking to fuck in GrAbove A in all genotypes Figure 4 a—c. Treatment with Al caused an increase in the contents of these antioxidants in the leaves of all four genotypes.
The effect of PEG stress on antioxidant contents varied with pH and genotype. The combined treatment of PEG and Al resulted in further increases in antioxidant contents relative to a single stress in Tibetan wild barley but, interestingly, decreased them in cultivated barley relative to Al stress alone Figure 4 a—c. The contents of these antioxidants also showed an increase in leaves under pH 4.
When plants were exposed to low pH, the MG content ificantly increased compared to the control pH 6. Al stress alone ificantly increased the MG content in all genotypes compared to pH 4. The comet assay, being a sensitive technique for the evaluation of DNA damage, was used to evaluate genotypic differences between Al and drought stresses alone or in combination Figure 6. Under control conditions, no DNA damage was observed in any genotype, and the DNA appeared as a densely condensed structure resembling a bead Figure 6 a—dand a similar result was found for those plants exposed to low pH Figure 6 e—h.
Under the pH 4.
The chloroplasts in all genotypes were normal under control conditions, but under stress, injuries became apparent in all genotypes Figure 7. Chloroplasts in control leaves contained dense thylakoids arranged in grana and membranes interconnecting with grana and their stroma lamellae also had localized starch grains Figure 7 a—d.
Plants of all four genotypes exposed to low pH did not show noticeable damage to the chloroplasts in all genotypes Figure 7 e—h. Under PEG stress, there was a visible rearrangement of thylakoid membranes and reduced starch grains in the chloroplasts.
These changes led to an almost complete unstacking of grana and a loose structure of thylakoids in all genotypes Figure 7 i—l. In the pH 4. Al-treated plants had comparatively more changes in chloroplast ultrastructure compared to the PEG-treated plants.
In particular, the of granal stacks was considerably reduced, the thylakoids were loosely arranged, and the thylakoid network was visibly incomplete Figure 7 q—t. Under pH 4.
In this work, decreased Pn was associated with ificantly reduced Gs and Tr, showing that stomatal factors inhibit photosynthesis. A substantial reduction in Gs could have resulted from the closure of stomata due to stress induction by the pH4. Moreover, Al and PEG caused a reduction in photosynthetic parameters Figure S3 and reduced plant growth and biomass Figures S1 and S2suggesting that Al in combination with PEG disrupted chloroplast and Chl-protein structures and deactivated the enzymes of the Calvin cycle, thereby impairing photosynthesis in the genotypes [ 25 ].
Thus, plants can avoid stresses by reducing transpiration. This study showed that barley plants subjected to pH 4.
Many kinds of environmental stresses have been shown to increase the levels of ROS in plant cells, including those associated with Al, drought, and salinity. ROS-detoxifying mechanisms are inherent in plants.Fat women looking to fuck in GrAbove A
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