Identification of Chlorophyll Fluorescence Parameters for Evaluating Drought Stress in Garden Plants

Does the enhanced tolerance of arbuscular mycorrhizal plants to water deficit involve modulation of drought‐induced plant genes?

Drought and heat stress are two major constraints that limit chickpea (Cicer arietinum L.) yield, particularly during seed filling. The present study aimed (i) to assess the individual and combined effects of drought and heat stress on oxidative metabolism during seed filling, and (ii) to determine any genetic variation in oxidative metabolism among genotypes differing in drought and heat tolerance and sensitivity. The plants were raised in outdoor conditions with two different times of sowing, one in November (normal-sown, temperatures <32°C-20°C (day–night) during seed filling), and the other in February (late-sown, temperatures >32°C-20°C (day–night) during seed filling). Plants were regularly irrigated to prevent any water shortage until the water treatments were applied. At both sowing times, the drought treatment was applied during seed filling (at ~75% podding) by withholding water from half of the pots until the relative leaf water content (RLWC) of leaves on the top three branches reached 42–45%, whereas leaves in the fully irrigated control plants were maintained at RLWC 85–90%. Drought-stressed plants were then rewatered and maintained under fully irrigated conditions until maturity. Several biochemical parameters were measured on the leaves and seeds at the end of the stress treatments, and seed yield and aboveground biomass were measured at maturity. Individual and combined stresses damaged membranes, and decreased PSII function and leaf chlorophyll content, more so under the combined stress treatment. The levels of oxidative molecules (malondialdehyde (MDA) and H2O2) markedly increased compared with the control plants in all stress treatments, especially across genotypes in the combined heat + drought stress treatment (increases in leaves: MDA 5.4–8.4-fold and H2O2 5.1–7.1-fold; in seeds: MDA 1.9–3.3-fold and H2O2 3.8–7.9-fold). The enzymatic and non-enzymatic antioxidants related to oxidative metabolism increased under individual stress treatments but decreased in the combined heat + drought stress treatment. Leaves had higher oxidative damage than seeds, and this likely inhibited their photosynthetic efficiency. Yields were reduced more by drought stress than by heat stress, with the lowest yields in the combined heat + drought stress treatment. Heat- and drought-tolerant genotypes suffered less damage and had higher yields than the heat- and drought-sensitive genotypes under the individual and combined stress treatments, suggesting partial cross-tolerance in these genotypes. A drought-tolerant genotype ICC8950 produced more seed yield under the combined heat + drought stress than other genotypes, and this was associated with low oxidative damage in leaves and seeds.

This study investigated the changes of leaf photosynthetic characteristic and chlorophyll fluorescence parameter responding to drought stress (DS) in two species of maize at elongating stage. The results of net photosynthesis rate (Pn) and light intensity response curve indicated that Pn reduced with enhanced light intensity. Photoinhibition in varying degrees appeared in different genotype varieties, and DS intensified the extent of photoinhibition. Results showed that for DS at elongating stage, Pn of the cultivar JD28 was insensitive to highlight. Pmax and Rd decreased, and physiological activity reduced obviously. Compared with JD28, JD261 decreased more. Moreover, DS resulted in decreased light compensation point (LCP) and light saturation point (LSP). And it caused highlight utilization ratio reduced but weak light use efficiency increased. JD28 had higher light use efficiency. Diurnal variation curve of Fv/Fm changed greatly in DS and there was no significant difference between the two species. DS treatments decreased photochemical quenching (qP), PhiPS2 and Fv’/Fm’, while it increased non-photochemical quenching (NPQ). The reduction of PhiPS2 was caused by the decrease of qP and Fv’/Fm’. DS treatments weakened maize leaves’ capability of assimilation, transformation and light energy utilization. JD28 could use more light than JD261 in photosynthesis. While JD261’s light use efficiency was lower, the less light used for photosynthesis and the excessive photon flux energy was dissipated in form of heat. Key words: Elongating stage, maize, drought-tolerance, photosynthesis.

Drought, a prevalent environmental stressor, has had significant consequences on soybean (Glycine max L.), notably impeding its growth and production. Therefore, it is crucial to gain insight into the regulatory responses of soybean plants exposed to drought stress during soybean flowering in the field. In this study, the cultivar 'Liaodou 15' was performed light drought (LD, 24.3% soil moisture content), moderate drought (MD, 20.6% soil moisture content) and severe drought (SD, 16.9% soil moisture content) treatments at flowering stages of soybean and then rehydrated (30% soil moisture content) until harvest. The yield-related indicators were measured and revealed that MD and SD treatments significantly reduced 6.3% and 10.8% of the 100-grain weight. Soybean plants subjected to three drought stresses showed that net photosynthetic rates were 20.8%, 51.5% and 71.8% lower in LD, MD and SD than that of CK. The WUE increased by 31.8%, 31.5% and 18.8% under three drought stress treatments compared to CK. In addition, proline content was 25.94%, 41.01% and 65.43% greater than that of CK under three drought stress treatments. The trend of the MDA content was consistent with that of the proline content. SOD activity was significantly increasing by 10.86%, 46.73% and 14.54% under three drought stress treatments. The activity of CAT in the SD treatment increased by 49.28%. All the indices recovered after rehydration. Furthermore, 54,78 and 51 different expressed metabolomics (DEMs) were identified in the LDCK/LD, MDCK/MD and SDCK/SD groups, respectively. There were 1,211, 1,265 and 1,288 different expressed genes (DEGs) were upregulated and 1,003, 1,819 and 1,747 DEGs were downregulated. Finally, combined transcriptomic and metabolomic analysis suggested that 437 DEGs and 24 DEMs of LDCK/LD group, 741 DEGs and 35 DEMs of MDCK/MD group, 633 DEGs and 23 DEMs of SDCK/SD group, were highly positively correlated in soybean plants under drought stress. Drought stress induced the expression of the PAO1, PAO4, PAO5 and P5CS genes to promote the accumulation of spermidine and proline. Our study elucidates the responses of drought-stressed soybean plants in the field and provides a genetic basis for the breeding of drought-tolerant soybean plants.

Sargent’s cherry trees (Prunus sargentiiRehder) are widely planted as an ornamental, climate change-sensing species. This study investigated changes in the soil moisture content, fresh weight, photosynthesis and chlorophyll fluorescence properties, and the chlorophyll and proline content of four-year-old P. sargentii seedlings after 30 days of drought stress. In the trees subjected to drought stress treatment, soil moisture content decreased, and the fresh weight of the aboveground part of the plant decreased. However, there was no significant difference in the root growth of the dried plants. Among the photosynthesis parameters, Pn MAX, E and gs showed a significant (p < 0.001) decrease after 15 days in dry-stressed seedlings, but there was no difference between treatments in WUE until 20 days, and there was a significant (p < 0.001) difference after 24 days. Chlorophyll fluorescence parameters, Fv/Fm, ΦPSII, Rfd, NPQ, and Pn MAX, also increased after 10 days in dry-stressed seedlings, but these changes did not reach statistical significance compared to the control treatment. These results may suggest that drought stress highly correlates with photosynthesis and chlorophyll fluorescence parameters. Chlorophyll content also significantly decreased in the seedlings under drought stress compared with the control treatment. The proline content decreased until the 10th day of drought stress treatment and increased after the 15th day, showing an increase of 10.9% on the 15th day and 57.1% on the 30th day, compared to the control treatment. These results suggest that photosynthesis, chlorophyll fluorescence parameters, and proline content can be used to evaluate drought stress in trees. The results of this study can contribute to the management of forests, such as the irrigation of trees when pore control ability and photosynthesis ability decrease.

PDF HTML阅读 XML下载 导出引用 引用提醒 金银花容器苗对干旱胁迫下接种根际促生细菌的生理响应 DOI: 10.5846/stxb201402180282 作者: 作者单位: 山东省林业科学研究院 作者简介: 通讯作者: 中图分类号: Q945; S718.83 基金项目: 山东省科技发展计划专项资助(2010GSF10621, 2014GNC113006) Physiological responses of Lonicera japonica container seedlings to plant growth- promoting rhizobacteria inoculation under drought stress Author: Affiliation: Shandong Academy of Forest,Shandong Engineering Research Center for Ecological Restoration of Forest Vegetation Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:在盆栽试验条件下,以金银花容器苗为试材,研究了不同干旱强度下接种蜡样芽孢杆菌(Bacillus cereus)L90对植物生理特征的影响。结果表明:随着干旱胁迫强度的增加,金银花容器苗的光合速率和气孔导度逐渐降低;而干旱环境下接种L90可显著提高气孔导度,缓解干旱胁迫对净光合速率的抑制;且干旱强度增加,缓解效果增强。接种B. cereus L90可显著抑制干旱胁迫下金银花容器苗PSⅡ最大光化学效率、实际光化学效率和光化学猝灭系数的降低,抑制非光化学猝灭系数的升高。虽然L90并没有提高对照处理中光合色素的绝对含量,但可显著抑制干旱环境下金银花叶片中光合色素的分解。干旱显著降低了金银花叶片中细胞分裂素含量,增加了脱落酸(ABA)的含量;在干旱胁迫下,接种L90可显著提高叶片中细胞分裂素的含量,并可促使根部产生的ABA运输到叶片中。干旱胁迫程度较轻时,L90对金银花容器苗的相对含水量和相对电导率影响不显著;而在重度干旱时,同对照相比,干旱及接种L90处理的相对含水量分别降低20.56%和10.21%,相对电导率分别提高31.42%和16.08%,接种L90处理的变化幅度明显较小。因此,干旱生境下接种B. cereus L90,可增加叶片中细胞分裂素含量,抑制光合色素的分解及光合能力的下降,提高金银花容器苗在干旱环境中的适应能力。 Abstract:Plant growth-promoting rhizobacteria (PGPR) are rhizosphere inhabitants that promote plant growth and suppress diseases. One of the proposed mechanisms through which PGPR enhance plant growth is the production of plant growth regulators, especially cytokinin. However, little information is available about the effects of cytokinin-producing PGPR inoculation on the drought stress response. Soil water availability is a crucial determining factor of plant yield, because drought stress inhibits stem elongation, leaf expansion, and stomatal movement. Therefore, a strain of rhizobacteria with a high rate of cytokinin production, Bacillus cereus L90, was selected for use in this investigation. The bacteria were obtained from the rhizosphere of a walnut tree, where water is limited and frequent dry periods occur. Serial dilution and a bioassay for the detection of cytokinin production were both used to isolate and screen the bacterial strain from the soil sample. This study investigated how PGPR affects the physiological characteristics of Lonicera japonica Thunb. under different drought stress treatments (light, moderate, severe, and a control). The combined effects of B. cereus L90 inoculation and various levels of drought stress on the photosynthetic characteristics, chlorophyll fluorescence parameters, photosynthetic pigment, cytokinin and ABA(abscisic acid) concentrations, relative water content, and relative electrolyte leakage were studied using the pot method. The results showed that the net photosynthetic rate and stomatal conductance decreased with increasing drought stress. However, B. cereus L90 inoculation was associated with an increase in stomatal conductance and net photosynthetic rate in plants under drought stress. B. cereus L90 inoculation reduced the negative impact of drought stress on the maximum photochemical efficiency of PSⅡ, the actual photochemical efficiency of PSⅡ, and the photochemical quenching coefficient. B. cereus L90 inoculation also prevented the non-photochemical quenching coefficient from increasing. Although no significant difference was observed under well-watered conditions, the leaves of inoculated drought-stressed L. japonica seedlings had higher photosynthetic pigments contents compared to those of non-inoculated seedlings. The roots of inoculated L. japonica seedlings had higher ABA content compared to non-inoculated seedlings. The elevated levels of cytokinins in L. japonica leaves and the higher concentration of ABA are both associated with drought stress. B. cereus L90 inoculation significantly increased the cytokinin content of drought-stressed L. japonica leaves, and improved the rate of transportation of ABA from the roots to the leaves. No significant differences in relative water content and relative electrical conductance were observed between inoculated and non-inoculated seedlings under light drought stress. Compared to the irrigated control, under severe drought stress, the relative water content of non-inoculated seedlings decreased by 20.56%, while that of inoculated seedlings decreased by 10.21%. However, the relative electrical conductance of inoculated and non-inoculated seedlings under severe drought stress increased by 31.42% and 16.08%, respectively. These results demonstrate that inoculation of B. cereus L90 under drought stress increases the cytokinin content of L. japonica leaves, and interferes with the suppression of photosynthetic pigments and net photosynthetic rate. Thus, B. cereus L90 inoculation could improve the adaptability ability of L. japonica seedlings to drought conditions. In conclusion, inoculation of cytokinin-producing PGPR could be used to alleviate drought stress and interfere with the suppression of physiological processes, showing real potential for practical use in arid environments as a drought stress inhibitor. 参考文献 相似文献 引证文献

Drought stress is one of the most important abiotic stresses, which greatly influences the photosynthesis of plants. The present study aimed to determine effects of drought stress to chlorophyll fluorescence parameters on tomato seedlings. In this paper, tomato seedlings were treated for 3, 6, 12 or 24 h by polyethylene glycol 6000 (PEG 6000) to simulate the drought stress. The effects of drought stress on chlorophyll fluorescence characteristics of tomato leaves and the characteristics of chlorophyll fluorescence parameters were analyzed by IMAGING-PAM modulated chlorophyll fluorescence in order to provide theoretical basis for tomato cultivation and breeding. The results showed that 1) the FM value of tomato seedlings after drought treatment was significantly lower than that without drought treatment about declined by 9.7%. 2) The value of Y (II) initially increased slightly and then decline eventually leveling off trend with the increasing of drought treatment time. 3) The ETR value was lower under drought stress than control check, especially when the drought stress treatment time up to 6 to 12 hours, the ETR value drops sharply, then increased slightly. 4) qP decreased from 0.646 to 0.4013 under the drought stress, which reflects the ability of oxidation of QA weakened, namely electron transfer activity of PS II decreased. 5) 15% PEG 6000 simulated drought stress treatment induced qN increased significantly.

Our results from iTRAQ-based proteomics extend the understanding of the mechanisms employed by AMF to defend against drought stress in blueberry. Arbuscular mycorrhizal fungi (AMF) can substantially contribute to plant drought tolerance. In this work, south highbush blueberry (Vaccinium corymbosum) ‘O’Neal’ cultivated with or without Funneliformis mosseae inoculation under well-watered or drought-stressed conditions were evaluated through an isobaric tag for relative and absolute quantitation (iTRAQ)-based proteomics approach. In total, 3078 proteins and 501 differentially abundant proteins (DAPs) were identified, including 127, 30, 236, and 108 DAPs in drought-stressed plants vs well-watered, drought-stressed plants with AMF inoculation vs well-watered plants with AMF inoculation, AMF-inoculated well-watered plants vs non-inoculated well-watered plants, and AMF-inoculated plants under drought stress vs non-inoculated plants under drought stress paired comparisons, respectively. Relative to non-inoculated plants, AMF-inoculated plants under drought stress maintained a greater abundance of DAPs involved in amino acid metabolism, antioxidant system, signal transduction, and photosynthesis including carbon fixation in photosynthetic organisms, porphyrin and chlorophyll metabolism, and carotenoid biosynthesis. Physiological analyses revealed that AMF-inoculated plants exhibited a greater photosynthetic capacity than non-inoculated plants under drought stress, mainly through non-stomatal factors such as enhancements of the efficiency of excitation energy capture by chloroplasts and the photochemical capacity of photosystems. Thus, the findings could explain the AMF-induced physiological effects associated with drought tolerance. Studies on the proteomic responses specific to AMF in drought-stressed plants will help to clarify how mycorrhization elicits improved plant growth and stress tolerance responses.

Bread wheat, one of the largest broadacre crops, often experiences various environmental stresses during critical growth stages. Terminal drought and heat stress are the primary causes of wheat yield reduction worldwide. This study aimed to determine the drought and heat stress tolerance level of a group of 46 diverse wheat genotypes procured from the Australian Grains Gene Bank, Horsham, VIC Australia. Two separate drought stress (DS) and heat stress (HS) pot experiments were conducted in separate growth chambers. Ten days after complete anthesis, drought (40 ± 3% field capacity for 14 days) and heat stress (36/22 °C for three consecutive days) were induced. A significant genotype × environment interaction was observed and explained by various morpho-physiological traits, including rapid, non-destructive infrared thermal imaging for computational water stress indices. Except for a spike length in DS and harvest index in HS, the analysis of variance showed significant differences for all the recorded traits. Results showed grains per spike, grains weight per spike, spike fertility, delayed flag leaf senescence, and cooler canopy temperature were positively associated with grain yield under DS and HS. The flag leaf senescence and chlorophyll fluorescence were used to measure each genotype's stay-green phenotype and photosystem II activity after DS and HS. This study identified the top ten best and five lowest-performing genotypes from drought and heat stress experiments based on their overall performance. Results suggest that if heat or drought adaptive traits are brought together in a single genotype, grain yield can be improved further, particularly in a rainfed cropping environment.

A new method in mitigation of drought stress by chitosan-coated iron oxide nanoparticles and growth stimulant in peppermint

The wheatgrass (Agropyron cristatum L.), is a plant with potential source of turf in arid and semi-arid regions. It can be also cultivated in order to prevent the soil erosion by coverage of earth's surface. Drought stress is one of the most important factors that influence growth and productivity of plants in arid and semi-arid condition. In order to evaluate the effect of trinexapac ethyl concentrations (0, 0.25 and 0.5 kg/h) and drought stress (25, 50 and 75% of field capacity) treatments on some wheatgrass morphological traits, a pot experiment was conducted as factorial in completely randomized block designs with four replications in research greenhouses of Islamic Azad University, Isfahan (Khorasgan) Branch during 2015. The results showed that the maximum plant height and the lowest amount of proline obtained in 75% drought stress treatment. The lowest fresh weight of the aerial parts and the relative water content (RWC) were observed in 25% drought stress treatment. The highest dry weight of the shoots was measured in control, 0.25 kg/h trinexapac-ethyl and 75% drought stress treatments. The highest proline content and the lowest height of the plants were observed in 25% drought treatment with 0.5 kg/h oftrinexapac-ethyl. In general, the research results indicated that under drought stress condition, application of trinexapac-ethyl by increasing the amount of proline and relative water content reduced stress damage and increased resistance to drought stress in the wheatgrass. Keywords: Agropyron cristatum L, Proline, Relative water content, Plant growth regulator.

The study aimed to determine the effect of a combination of drought stress and nano-silica treatments to increase the content of antioxidant compounds and antioxidant activity of lemongrass [Cymbopogon citratus (DC. ex Nees) Stapf] and determine the optimal combination. The research used a Completely Randomized Design (CRD) with two factors with 5 replications. The first factor was the level of drought stress (without drought stress, moderate, and severe). The second factor was the nano-silica dose, (0 mg/L, 125 mg/L, and 250 mg/L) with a volume of 10 mL per plant. The parameters measured were carotenoid content, proline content, total phenolics content, and antioxidant activity. Data were analyzed using Analysis of Variance (ANOVA) and Duncan’s Multiple Range Test (DMRT). The results showed that there is a specific combination of drought stress and nano-silica which can increase the content of carotenoids, proline, total phenolics, and antioxidant activity in lemongrass. The treatment of moderate and severe drought stress with 125 and 250 mg/L nano-silica increased the carotenoid and proline content maximally. Higher total phenol content and antioxidant activity were obtained from the combination of 250 mg/L nano-silica without drought stress. The highest chlorophyll content was recorded from the combination of severe drought stress and 250 mg/L nano-silica. Drought stress treatment with 250 mg/L nano-silica could increase the antioxidants of lemongrass plants, but maximum production of antioxidants required different combinations of drought stress and nano-silica treatments. Nano-silica treatment at a dose of 250 mg/L in conditions of sufficient water or lack of water can be an optimal combination treatment in lemongrass cultivation.

In order to screen candidate aquaporin genes involved in resisting osmotic stress, we analyzed the physiological responses and the expression levels of aquaporin genes in garlic under drought and salt stress with ‘Er Shuizao’ as plant material. Different physiological indicators were detected under drought and salt stress treatments. RT-qPCR was used to detect the expression levels of the candidate aquaporin genes in specific tissues. Finally, we screened AsPIP1-3 as a candidate gene and analyzed its function. The results showed that the relative water content and chlorophyll content of leaves decreased, the O2− production rate increased, and H2O2 accumulated in garlic under drought and salt stress. The activities of SOD, POD, and CAT enzymes first increased and then decreased in garlic. The content of soluble sugar and proline increased to maintain cell osmotic balance, and the content of MDA and relative conductivity continued to increase. Most aquaporin gene expression first increased and then decreased in garlic under drought and salt stress. AsPIP1-3 gene expression is up-regulated under drought and salt stress in garlic. The relative expression was the highest on the 6th day of stress, being related to antioxidant enzyme activity and osmotic regulation. The consistent changes in gene expressions and physiological responses indicated that AsPIP1-3 played a role in resisting garlic osmotic stress. AsPIP1-3 was located on the cell membrane, being consistent with the predicted results of subcellular localization. The germination rate and root length of transgenic Arabidopsis under drought stress were significantly different from the wild type. Drought stress reduced the ROS accumulation of transgenic Arabidopsis, and the antioxidant enzyme activity was significantly higher than the wild type. The relative conductivity and MDA content significantly decreased, and the proline content increased under drought stress. The expression level of the genes related to drought stress response (AtRD22, AtP5CS, AtABF3, and AtLEA) significantly increased. The overexpression of AsPIP1-3 genes improved the drought tolerance of transgenic Arabidopsis plants, showing that AsPIP1-3 proteins enhanced drought tolerance. Our study laid a foundation for exploring the regulatory mechanism of garlic to abiotic stress.

Although drought and defoliation stress have been shown to reduce soybean [Glycine max (L.). Merr.] yield, little information has been published regarding their effects on soybean seed quality. Field experiments were conducted in 1986, 1987, and 1989 to evaluate the effect of drought and defoliation (1989 only) stress during soybean seed development on seed germination and vigor. Essex (MG [maturity group] V) and Union (MG III) were grown in 1986 and 1987, and Harper (MG III) and McCall (MG 00) in 1989. Moisture treatments were either well watered or drought stressed during seed development (R5 to R7). In 1989, a total defoliation treatment was also imposed at R6 as an additional stress factor. There were significant reductions in yield and yield components following drought stress in all 3 yr and following defoliation in 1989. Leaf conductance and transpiration also decreased in the drought stress treatments. There was no effect of drought stress on seed germination or seed vigor as measured by accelerated aging germination and the cold test across the four cultivars (determinate and indeterminate) and 3 yr. In 1989 slight changes in 3‐d germination and conductivity occurred for some drought stress treatments. Most of this response, however, was related to increased occurrence of hard seed, which does not represent an indication of a change in vigor. Seed germination and vigor were significantly reduced for small, flat, shriveled, and underdeveloped seeds that only occurred following defoliation. These seeds represented a small portion of the seed lot that would normally be removed during conditioning. The data suggest that drought stress would have no effect on seed germination or vigor, unless the stress was severe enough to produce shriveled, flat, underdeveloped seeds.

Can chlorophyll-a fluorescence parameters be used as bio-indicators to distinguish between drought and salinity stress in Tilia cordata Mill?