Symptoms Of Salt Injury Research Articles

AtMYB72 aggravates photosynthetic inhibition and oxidative damage in Arabidopsis thaliana leaves caused by salt stress

ABSTRACT MYB transcription factor is one of the largest families in plants. There are more and more studies on plants responding to abiotic stress through MYB transcription factors, but the mechanism of some family members responding to salt stress is unclear. In this study, physiological and transcriptome techniques were used to analyze the effects of the R2R3-MYB transcription factor AtMYB72 on the growth and development, physiological function, and key gene response of Arabidopsis thaliana. Phenotypic observation showed that the damage of overexpression strain was more serious than that of Col-0 after salt treatment, while the mutant strain showed less salt injury symptoms. Under salt stress, the decrease of chlorophyll content, the degree of photoinhibition of photosystem II (PSII) and photosystem I (PSI) and the degree of oxidative damage of overexpressed lines were significantly higher than those of Col-0. Transcriptome data showed that the number of differentially expressed genes (DEGs) induced by salt stress in overexpressed lines was significantly higher than that in Col-0. GO enrichment analysis showed that the response of AtMYB72 to salt stress was mainly by affecting gene expression in cell wall ectoplast, photosystem I and photosystem II, and other biological processes related to photosynthesis. Compared with Col-0, the overexpression of AtMYB72 under salt stress further inhibited the synthesis of chlorophyll a (Chla) and down-regulated most of the genes related to photosynthesis, which made the photosynthetic system more sensitive to salt stress. AtMYB72 also caused the outbreak of reactive oxygen species and the accumulation of malondialdehyde under salt stress, which decreased the activity and gene expression of key enzymes in SOD, POD, and AsA-GSH cycle, thus destroying the ability of antioxidant system to maintain redox balance. AtMYB72 negatively regulates the accumulation of osmotic regulatory substances such as soluble sugar (SS) and soluble protein (SP) in A. thaliana leaves under salt stress, which enhances the sensitivity of Arabidopsis leaves to salt. To sum up, MYB72 negatively regulates the salt tolerance of A. thaliana by destroying the light energy capture, electron transport, and antioxidant capacity of Arabidopsis.

Rootstock mediated alteration in morphology and photosystem in sweet orange (Citrus sinensis) scion cv. Pusa Sharad under NaCl stress

There is a dearth of rootstock studies on how salinity stress imparts tolerance to the scion cultivar in citrus [Citrus sinensis (L.) Osbeck]. The impact of sodium chloride on sweet orange cv. Pusa Sharad (PS) grafted on 11 different rootstocks i.e. Jatti khatti (JK), X–639 (X9), CRH–12 (C12), NRCC–1 (N1), NRCC–2 (N2), NRCC–3 (N3), NRCC–4 (N4), NRCC–5 (N5), Troyer citrange (TC), CRH–47 (C47) and Cleopatra mandarin (CM) was evaluated at the nursery unit of ICAR-Indian Agricultural Research Institute, New Delhi, during 2019–22. Irrigation water containing 30 and 60 mM of sodium chloride (NaCl) was applied to scion/rootstock combinations in comparison to control (without NaCl) till the onset of salt injury symptoms i.e. 42 days. Under salinity stress, the PS scion grafted onto CM, X9, C47, N1, and N3 rootstocks exhibited minimum reduction in the scion height, leaf area ratio, root to shoot ratio, total chlorophyll content, total carotenoid content, transpiration rate, photosynthesis rate, internal CO2 concentration and stomatal conductance as compared to PS scions grafted onto JK, C12, N2, N4, N5, and TC rootstocks under 60 mM NaCl stress. Results showed that specific rootstock can enhance salt-tolerance potential by increasing pigment content and strengthening the photosystem. PS scions grafted onto CM, C47, X9, N1, and N3 demonstrated greater NaCl tolerance compared to those grafted onto JK, C12, N2, N4, N5, and TC and hence recommended for areas having salinity level up to 60 mM.

Morphogenetic Response of Assorted Rice Genotypes to Salinity in Tanzania

Salinity, where salts concentrate on the soil surface causing severe decline of crop yields, is a worldwide problem. In Tanzania salinity is one of the major soil degradation challenges affecting over 3.5 million hectares limiting agriculture productivity of various crops including rice. Most of the varieties grown are sensitive to salts and inadequate tolerant cultivars available in the country. A hydroponics mass screening technique using Yoshinda Solution was used to test the 102 genotypes in NaCl- saline treated and non-treated solution at Tanzania Agricultural Research Institute (TARI-Dakawa Centre). Different salt concentrations (4 dSm-1, 6 dSm-1, 8 dSm-1 and 10 dSm) were used and the experiment was done in three replications. The genotypic variability for salinity tolerance was observed as less salt injury symptoms, low Na+ accumulation and Na+/K+ ratio in plant tissues and high biomass accumulation (fresh weight and dry weight). Results revealed further those 28 genotypes (28.45%) out of 102 showed tolerance to salinity, at high salinity level of 10dSm-1. Lines namely SR35266-2-18-2-1, SR35250-1-19-1-1, SR23364-128-1762-1-HV-1-1, SR35230-1-12-1-1, SR23364-128-1986-1-HV-1-1, SR34590-HB3433-4-1-1, SR35266-2-7-1-1, PBR1000922-1 and SR34053 (#5-52)-1-4-2-10-3-3 showed high performance under high salt conditions. Others includes SR35266-3-1-5-1, SR34574-2-10-3-1-2-1, SR35278-2-10-1-1, SR35250-2-3-1-1, SR35266-3-2-3-1, SR35266-3-2-4-1, SR23364-133-184-1-HV-1-1, SR34592-HB-1-HV-1, and SR34042F3-22-1-1-5-3 indicated tolerance to salt and had high dry matter as well. All the genotypes had increased levels of Na+ and differential performance was observed in some genotypes under saline and non-saline conditions. Among these three lines namely SR35266-2-7-1-1, SR23364-128-1762-1-HV-1-1, and SR34590- HB3433-4-1-1expressed high dilution ability as the K+ and Na+ concentrations were lower compared to other genotypes. The study, therefore, suggests that the lines can be used in breeding programs to develop varieties with potential to salt tolerance and other traits.

Chemical Seed Priming to Improve Salinity Tolerance in Rice

A study was conducted at Rice Research Station, Vyttila to assess the effect of seed priming in improving the salinity tolerance of rice varieties. The study consisted of two parts. In the first part, screening of rice varieties for salinity tolerance was done and in the second experiment, the effect of priming on salinity tolerance was assessed. The first experiment was a laboratory study to screen three rice varieties, namely, Jyothi, Uma and Vyttila-10 at five salinity levels i.e., non-saline, 3 dS m-1, 6 dS m-1, 9 dS m-1 and 12 dS m-1. Results showed that Jyothi was susceptible to 6 dS m-1 salinity at 16 days after sowing (DAS). Uma was moderately tolerant and became susceptible to 6 dS m-1 at 21 DAS. Vyttila-10 was highly tolerant to 6 dS m-1 salinity but it was susceptible to the salinity level of 9 dS m-1 at 21 DAS. In the second experiment, seeds of these varieties were primed with three chemicals namely beta-amino butyric acid @ 1 mmol L-1, calcium chloride @ 2% and sodium nitroprusside @ 100 µM and with water as control. The seedlings of Jyothi and Uma were raised at salinity levels of 6 dS m-1 and 9 dS m-1, while seedlings of Vyttila-10 were raised at salinity levels of 9 dS m-1 and 12 dS m-1. The efficacy of each priming chemical was analyzed based on germination percentage, growth parameters and visual salt injury symptoms. Priming seeds with calcium chloride was found to improve the growth and salinity tolerance of rice seedlings and could be a reliable method to combat the salinity stress of rice in the initial stages of crop growth.

Phenotypic Differences and Physiological Responses of Salt Resistance of Walnut with Four Rootstock Types.

Walnut is one of the world’s four largest nuts. Currently, the bottleneck in walnut breeding is the production of resistant variants. Soil salinization is a global problem, and the use of salt-tolerant rootstocks is a basic strategy to overcome the challenge of sustained walnut production. Providing a scientific basis for the selection of walnut salt-tolerant rootstocks is possible by studying the physiological and biochemical response characteristics and salt tolerance variations of different walnut genotypes under salt stress. In the present study, seedlings of four genotypes of walnut rootstocks, including J1 (Juglans hindsii), J2 (J. mandshurica), J3 (J. regia × J. mandshurica), and J4 (J. regia × J. hindsii), were employed as test materials to conduct a 28-day pot experiment under NaCl stress with five NaCl concentrations (0, 50, 100, 200, and 300 mmol/L). Under different NaCl treatment concentrations, seedling morphology, growth indices, chlorophyll content, photosynthetic parameters, relative electrical conductivity (REC), malondialdehyde (MDA), proline (Pro), soluble sugar (SS), and the activity of superoxide dismutase (SOD) and peroxidase (POD) in the leaves were examined. Salt stress altered the morphological characteristics and growth indices of seedlings from four genotypes to varying degrees. In addition, according to the analysis of physiological and biochemical data, salt stress had a considerable impact on both the physiological and biochemical processes of seedlings. Salt stress decreased the chlorophyll content and photosynthetic parameters of four genotypes, the REC, MDA content, Pro content, and SS content of each genotype increased by different degrees, and the enzymatic activities showed different trends. The salt tolerance of rootstocks was evaluated thoroughly using principal component analysis and membership function analysis based on the 16 parameters. The results of a comprehensive evaluation of salt tolerance showed that the order of salt tolerance of the four genotypes was J4 > J1 > J3 > J2, which corresponded to the order of the morphological symptoms of salt injury. In conclusion, J4 has strong salt tolerance and is an important germplasm resource for walnut salt-tolerant rootstock breeding.

Improvement of Rice Breeding for Salinity Tolerance

Rice is one of the most significant food crop of the world. The production of rice is the second-highest in the world. Salinity is a serious constraint to increase rice production worldwide. Review of recent efforts achieved towards rice breeding for salinity tolerance has a paramount importance beside for rice production improvement in Ethiopia. Rice is a relatively new crop to Ethiopia; however, the crop is relatively well adapted to different parts of the country. Salinity is a problem of many irrigated, arid and semi-arid areas of the world where rain fall is insufficient to leach out salts from the root zone. Typical symptoms of salt injury in rice are stunted growth, leaf rolling, white leaf tip, white blotches in the leaf blade, drying of the older leaves and poor root growth. The main mechanisms of salt tolerance are control of salt uptake, reducing damage under excessive ion uptake and osmotic adjustment. The three major breeding approaches for salinity tolerant varietal development are conventional breeding, marker assisted selection and genetic engineering. Conventional rice breeding approaches exercised for thousands of years. But, the progress is slow, due to the time consuming process, the quantitative nature of most agronomic traits make difficulties in genotypes selection. However, modern breeding is more precise and efficient and easily identify undesirable genes that can be eliminated in future generations. In rice, markers like RAPDs, AFLPs, ISSRs and SSRs have been used. Among these DNA markers, SSRs is highly preferable for gene tagging and mapping efforts. The development of salt-tolerant variety by transgenic way needs more investigation. To date, transgenic salt tolerant variety has not yet reached at farmers’ field. In Ethiopia a little beat was done to identify rice genotypes adaptable to adverse saline soil conditions. From here on, more research findings highly crucial for the development of salinity tolerant rice varieties in the country. Therefore, it is a good opportunity for rice breeders to develop salt tolerant high yielding varieties in Ethiopia. Keywords : Conventional breeding, Genetic engineering, Marker-assisted selection, Rice, Salt tolerance DOI: 10.7176/JEES/10-5-02 Publication date: May 31 st 2020

Tissue sodium and chloride concentrations in relation to needle injury in boreal conifer seedlings subjected to salt stress

Tissue Na and Cl concentrations can be used for estimation of salt injury for white spruce, black spruce, and jack pine growing at salt affected areas. Elevated soil salinity is among the most challenging environmental factors affecting plant growth and survival. Due to the widespread salinity concerns in agricultural soils, most of the salinity research has been carried out with agricultural crop plants. However, salinity is also frequently a factor affecting the sites reclaimed following surface mining including the oil sands mining areas located in the boreal forest of the northeastern Alberta, Canada. The present study examined the relationship between NaCl uptake, tissue Na and Cl concentrations, and plant injury in seedlings of three conifer species, which are commonly used for oil sands reclamation including black spruce (Picea mariana), white spruce (Picea glauca), and jack pine (Pinus banksiana). The seedlings were grown under controlled-environment conditions in sand culture and were subjected to 0 (control), 30, 60, and 90 mM NaCl treatments. Compared with control, stem diameters and shoot heights of black spruce, white spruce, and jack pine seedlings were significantly reduced by all NaCl treatments. White spruce and jack pine also exhibited reduced total dry weights. Needle chlorophyll concentrations decreased under NaCl treatments in all species. Visible symptoms of salt injury were observed in young and old needles of seedlings treated with NaCl. Significant needle necrosis was present in all species subjected to the 90 mM NaCl treatment. We found significant correlation between needle Na and Cl concentrations and necrosis extent. Therefore, we propose using the tissue Na and Cl concentration as an effective monitoring tool to estimate salt injury of conifers grown in NaCl-affected areas.

Relationship of Salinity Tolerance to Na+ Exclusion, Proline Accumulation, and Antioxidant Enzyme Activity in Rice Seedlings

Rice is a staple crop for over 50% of the world’s population, but its sensitivity to salinity poses a threat to meeting the worldwide demand. This study investigated the correlation of salinity tolerance to Na+ exclusion, proline accumulation, and the activity of antioxidant enzymes in some rice cultivars originating from Egypt. Giza 182 was shown to be the most tolerant of the five cultivars, as judged by visual symptoms of salt injury, growth parameters, and patterns of Na+ accumulation, while Sakha 105 appeared to be highly susceptible. In detail, Giza 182 accumulated the lowest Na+ concentration and maintained a much lower Na+/K+ ratio in all plant organs in comparison to Sakha 105. The salinity-tolerant varieties had higher accumulation of proline than the salinity-susceptible cultivars. The salinity-tolerant Giza 182 accumulated a higher concentration of proline, but the lipid peroxidation (MDA) level was significantly reduced compared to in the salinity-susceptible Sakha 105. In addition, Giza 182 had stronger activity of both catalase (CAT) and ascorbate peroxidase (APX) compared to Sakha 105. The findings of this study reveal that the salinity tolerance in rice is primarily attributable to Na+ exclusion, the accumulation of proline in rice organs, a low Na+/K+ ratio, and a low level of lipid peroxidation. The levels of the antioxidant enzymes CAT and APX and the accumulation of proline may play important roles in salinity tolerance in rice. However, the comparative involvement of individual antioxidant enzymes in salinity stress in rice should be further investigated. Giza 182 has the potential to be cultivated in salinity-affected areas, although the effects of salinity stress on its grain yield and quality should be evaluated during the full crop cycle.

Evaluation of guava (Psidium guajava) and bael (Aegle marmelos) under shallow saline watertable conditions

Growth, physiological activities and leaf ionic relations were studied in guava (Psidium guajava L.) cv. Allahabad Safeda and bael (Aegle marmelos Correa) cv. NB-5 planted under shallow saline watertable conditions. Marginally saline (MSW; ECIW 4 dS/m) and saline (SW; 6 dS/m) waters were applied either in cyclic (C) mode with the best available water (BAW; 2.8 dS/m) or regularly (R) to impose five salinity levels: control (BAW), CMSW (MSW and BAW in cyclic mode), RMSW (regular application of MSW), CSW (SW and BAW in cyclic mode) and RSW (regular application of SW). Data were recorded 120 days after salt treatment (DAST). In CSW and RSW treatments, salt injury symptoms (leaf yellowing, marginal scorch and chlorosis) appeared around 60 DAST in both the crops. Although plant height and stem girth were relatively less affected, branch and leaf emergence considerably decreased with increase in salinity giving the salinized plants a sparse look. Regular irrigation with 6 dS/m water caused substantial reductions in net photosynthesis (37-45%), photochemical efficiency (Fv/Fm ratio; 11-21%) and total soluble sugars (≈30%); and increase in proline, Na+ and Cl- levels in leaves. Leaf proline was nearly fivefold higher in guava and threefold higher in bael at 6 dS/m salinity than BAW irrigated plants. Both the crops exhibited ≈8 fold higher leaf Na+/K+ ratio and considerable increase in leaf Cl- when continuously irrigated with 6 dS/m water. Plant growth, physiological attributes and leaf ionic composition in CMSW treatment were comparable to BAW treated plants indicating that marginally saline water (ECIW ≈ 3-4 dS/m) can be used to irrigate guava cv. Allahabad Safeda and bael cv. NB-5 planted in saline soils.

Ectopic expression of Limonium bicolor (Bag.) Kuntze DREB (LbDREB) results in enhanced salt stress tolerance of transgenic Populus ussuriensis Kom

High salinity is one of the most common abiotic stresses that plants have to confront, and selecting salt-tolerant plants is becoming a very important task in breeding. In this study, non-transgenic (NT) and three LbDREB-transgenic Populus ussuriensis Kom. (Dr22, Dr8, and Dr2) lines were treated with 150 mM NaCl. The salt tolerance of NT, Dr2, Dr8, and Dr22 were evaluated and compared. Phenotypic observation, chlorophyll content detection and leaf salt injury index calculation suggested NT exhibited more severe salt injury symptoms and weaker photosynthetic capacity than Dr2, Dr8, and Dr22. LbDREB gene exhibited opposite temporal expression patterns with no apical meristem (NAM), trihelix transcription factor (GT-1) and WRKY transcription factor 70 (WRKY70), and consistent expression patterns with Cu–Zn superoxide dismutase and peroxidase-PO1 genes, in Dr2, Dr8, and Dr22 under salt stress. The superoxide dismutase and peroxidase activities of transgenic lines were higher than NT plants during the salt stress treatment. Malonaldehyde accumulation in NT leaves was more significant than in transgenic leaves, while proline accumulation in NT leaves was much less than that in transgenic leaves under salt stress. The root to shoot ratios were significantly increased in Dr2, Dr8, and Dr22 plants, but were slightly decreased in NT plants, 12 days after salt stress treatment. The relative water content of NT leaves decreased more than transgenic leaves, meanwhile, the relative electrolytic leakage of NT leaves increased more significantly than transgenic leaves after salt stress. In summary, Dr2, Dr8, and Dr22 exhibited stronger salt stress tolerance than NT. The transgenic lines Dr2, Dr8, and Dr22 can serve as alternative salt-tolerant germplasm resources in P. ussuriensis breeding.

Effect of Salt on Growth of Rice Landraces in Vietnam

In this study, total 41 Vietnamese rice landraces were evaluated for their salt tolerance in the laboratory and field conditions. Amongst them, 15 landraces have shown moderate to high salinity tolerance in both screening conditions. The three landraces Chanh trui, Cuom dang 2 and Nep cuc have revealed the highest salt tolerance which were similar to the Pokkali. However, with time and levels of salt treatments, salt injury symptoms were clearly observed in all landraces with different symptoms. All plants growth parameters were remarkably reduced in all landraces under increasing salt-treated concentrations. By use of molecular marker RM217 linked with salinity tolerance QTL located on the chromosome 4, 11 landraces have been found to carry the allen involving in salt tolerance. This study has provided useful information on salinity tolerance of rice landraces for breeding programs to deal with the climate change in this country.

Effect of Salt on Growth of Rice Landraces in Vietnam

In this study, total 41 Vietnamese rice landraces were evaluated for their salt tolerance in the laboratory and field conditions. Amongst them, 15 landraces have shown moderate to high salinity tolerance in both screening conditions. The three landraces Chanh trui, Cuom dang 2 and Nep cuc have revealed the highest salt tolerance which were similar to the Pokkali. However, with time and levels of salt treatments, salt injury symptoms were clearly observed in all landraces with different symptoms. All plants growth parameters were remarkably reduced in all landraces under increasing salt-treated concentrations. By use of molecular marker RM217 linked with salinity tolerance QTL located on the chromosome 4, 11 landraces have been found to carry the allen involving in salt tolerance. This study has provided useful information on salinity tolerance of rice landraces for breeding programs to deal with the climate change in this country.

Effect of NaCl Tolerance on Photosynthetic Physiology and Growth of Seedlings of Three Poplar Clones

We studied the response of photosynthetic physiological characteristics of three poplar clone seedlings to Na Cl stress with three kinds of poplar( Populus L.) clones of poplar( Populus L.) clone seedlings including‘A5'( Populus pseudo-simonii × P. nigra) ×( P. simonii × P. nigra),‘J7'( P. deltoidis × P. catyana CL.‘J7') and ‘1344'( P. deltoids × P. cathayana CL.‘1344') in Heilongjiang Province. Three Na Cl stress treatments were established at the contents of 0. 3%,0. 5% and 0. 7%( percentage of Na Cl in total dry soil mass). The salt injury symptoms first appeared in ‘1344 'under Na Cl stress,followed by ‘J7 'and ‘A5 '.Furthermore,under the same Na Cl content,the maximum damage due to Na Cl stress also occurred first in‘1344',followed by ‘J7'and ‘A5'. The mean tree diameter at breast height and total tree height differed signi? cantly under three Na Cl stress treatments. Moreover,the difference between three Na Cl stress treatments gradually become bigger,which was 10%- 35% lower than the control treatment during the late period of this experiment. With the increase of Na Cl,the chlorophyll content decreased,with the decrease in ‘J7 'being much more obvious than in ‘A5'and ‘1344'. With the increase of Na Cl,the content of carotenoid in ‘A5'increased,and ‘J7 'and ‘1344 'decreased. Chlorophyll b content under 0. 3% Na Cl stress in ‘A5 'and‘1344'was higher than that in the control,while the‘A5'chlorophyll b content under the 0. 5% and 0. 7%Na Cl stress levels were in contrast not significantly different,but ‘1344'under 0. 3% and 0. 5% Na Cl stress levels was significantly higher than that in the control and the 0. 7% Na Cl stress level. ‘J7 ' showed no significant difference when compared with the 0. 3% Na Cl stress,but was higher than the 0. 5% and 0. 7%levels. The photosynthesis of the clone seedlings reduced due to the Na Cl stress. The Gsand Ciof the leaves decreased with the increase of the salt,while the Lsmainly decreased. One possible explanation for the phenomenon in this study may be that the photosynthetic physiology was greatly influenced by stomatal limitation and non-stomatal limitation. The WUE of three poplar seedlings under Na Cl was maintained at a higher level,which may suggest that these poplar seedlings have a strong resistance to Na Cl stress. Therefore,‘A5'had the strongest salt-tolerant ability among these three clones.

Effects of salinity on leaf mineral composition and salt injury symptoms of some Iranian wild grapevine (<em>Vitis vinifera</em> L. ssp. sylvestris) genotypes

<p style="text-align: justify;"><strong>Aim</strong>: To evaluate the suitability of wild grapevine genotypes to saline conditions by measuring leaf ion content and salt injury symptoms.</p><p style="text-align: justify;"><strong>Methods and results</strong>: Vines of nine wild (<em>Vitis vinifera</em> L. ssp. sylvestris) genotypes were planted in pots and after the good establishment, salinity treatments (0, 50, 100 and 150 mM NaCl) started. At the end of the experimental period, the K<sup>+</sup>, Na<sup>+</sup>, NO<sub>3</sub><sup>-</sup> and Cl<sup>-</sup> content of leaves and visible symptoms of salt injury were recorded. Leaf Na<sup>+</sup> and Cl<sup>-</sup> content increased with increasing salinity but levels and accumulation rates were different among genotypes.</p><p style="text-align: justify;"><strong>Conclusion</strong>: Based on Na<sup>+</sup> and Cl<sup>-</sup> content and salt symptoms, genotypes 4 and 7 showed less symptoms than the other genotypes at moderate (50-100 mM) NaCl concentration and none could tolerate high salt (150 mM) concentration.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: Under saline conditions, ion accumulation in the leaves significantly varied among wild genotypes and some of them could be recommended as saline tolerant genotypes.</p>

Productivity and Quality Responses of Salt-Stressed Roses to Supplemental Calcium

Plants of Rosa × spp. L. ‘Happy Hour’ grafted on the rootstocks R. × ‘Manetti’ and R. × ‘Natal Briar’ were salinized with 12 mM NaCl and received supplemental calcium (Ca) applications (as CaSO4) of 0, 2.5, 5.0, 7.5 and 10 mM. Additional plants were salinized with 6 mM Na2SO4 and supplemented with 5 mM CaSO4 and compared to non-salinized, no supplemental Ca control plants. Cumulative flowers harvested, shoot length and leaf chlorophyll index were similar for both rootstocks across salt treatments, but Manetti plants had higher dry weights in flowers and most plant tissues except roots. Productivity and water relations in NaCl-salinized plants were not responsive to supplemental Ca. Conversely, calcium-supplemented plants salinized with Na2SO4 had better productivity and quality than those with NaCl, and were similar to non-stressed control plants. Salt injury symptoms were evident only on NaCl-treated plants, regardless of Ca supplements, and closely associated with chloride, but not sodium, accumulation, in leaf tissues. The extent of the ameliorative properties of supplemental calcium applications on salinized rose plants is influenced by the salinity level, the chemical composition of the salinizing solution (major ions and counter-ions) and the cultivar (scion) and rootstock selection.

Physiological and growth changes in micropropagated Citrus macrophylla explants due to salinity

Salinity is one of the major abiotic stresses affecting arable crops worldwide, and is the most stringent factor limiting plant distribution and productivity. In the present study, the possible use of in vitro culture to evaluate the growth and physiological responses to salt-induced stress in cultivated explants of Citrus macrophylla was analyzed. For this purpose, micropropagated adult explants were grown in proliferation and rooting media supplemented with different concentrations of NaCl. All growth parameters were decreased significantly by these NaCl treatments; this was accompanied by visible symptoms of salt injury in the proliferated shoots from 60mM NaCl and in the rooted shoots from 40mM NaCl. Malondialdehyde (MDA) increased with increasing salinity in proliferated shoots, indicating a rising degree of membrane damage. The concentration of total chlorophyll significantly decreased in the presence of NaCl, and this effect was more pronounced in the rooted explants. The Na(+) and Cl(-) concentrations in the explants increased significantly with the salinity level, but Cl(-) levels were higher in the proliferated explants than in the rooted explants. For osmotic adjustment, high concentrations of compatible solutes (proline and quaternary ammonium compounds-QAC) accumulated in salt-stressed plants in proliferation, but differences were not observed in rooted explants. In proliferation, proline and QAC were highly correlated with the sodium and chloride concentrations in the explants, indicating a possible role of these compounds in osmotic adjustment. The plant concentrations of NO(3)(-), K(+), Mg(2+), Ca(+) and Fe were also affected by the NaCl concentration of the medium. We suggest that the important deleterious effects in the in vitro explants of Citrus macrophylla grown at increasing NaCl concentrations were due mainly to toxic effects of saline ions, particularly Cl(-), at the cellular level.

Ornamental characters, ion accumulation and water status in Arbutus unedo seedlings irrigated with saline water and subsequent relief and transplanting

Arbutus unedo seedlings were grown in a greenhouse and submitted to three irrigation treatments (salinity period) using solutions with an EC of 0.85 dS m −1 (control treatment), 5.45 dS m −1 (S1) and 9.45 dS m −1 (S2). After 16 weeks, growth and ornamental characters, leaf water potentials, gas exchange and ion concentrations were determined. After the salinity period, plants were exposed to a relief period for 1 month, whereby half of the plants were transplanted to field conditions and the other half into 24 cm diameter plastic pots. Salinity induced a significant decrease in shoot biomass and leaf area but root/shoot ratio was increased. Plant height was significantly inhibited by salinity. The ornamental characters were affected in the treated plants, with symptoms of salt injury, such as burning of leaf margin. Leaf water potentials decreased with increasing salinity, more significantly at predawn than at midday. The relationship between net photosynthesis ( P n) and leaf conductance ( g l) was linear for all treatments and the same values of P n are associated with lower values of g l for the saline treatments than for control treatment. The concentration of Cl − in leaves increased with increasing salinity and was higher than the corresponding concentration of Na +. Na + and Cl − contents were higher in the leaves than in the roots in both saline treatments. The K + and Ca 2+ levels were lower in the treated plants than in control plants and applied salinity reduced the K +/Na + ratio in leaves, stems and roots, the decrease being much greater for leaves than for roots. The Ca 2+/Na + ratio fell with salinity in all parts of the plants. At the end of the relief period leaf water potentials were recovered mainly in field conditions. S2 treatment showed lower values of P n and g l than control and S1 treatments in pot conditions and in field conditions S1 showed the lowest values for P n and g l.

Responses of the cherry rootstock to salinity in vitro

The in vitro response of sweet cherry rootstock Gisela 5 (Prunus cerasus × Prunus canescens) to increasing concentrations of NaCl (0, 50, 100 and 150 mM) in the Murashige and Skoog culture medium was studied. Induced salinity reduced growth and chlorophyll content in shoots but had no effect on water content. The increase in malondialdehyde content indicated that salinity induced oxidative stress which was accompanied with the visible symptoms of salt injury in the shoots. Antioxidant enzymes, such as superoxide dismutase, ascorbate peroxidase, peroxidase, catalase, and glutathione reductase were also significantly elevated. Although no change was observed in the Cl concentration, Na concentration of shoots significantly rose and NaCl treatments impaired K, Ca and Mg nutrition and induced imbalance in K:Na and Na:Ca ratios.

Comparative Morphological and Physiological Responses of Green Gram Genotypes to Salinity Applied at Different Growth Stages

Experiments ere conducted to find the difference among green gram (Vigna radiata L. Wilczek) genotypes for salinity tolerance during germination and during vegetative and reproductive growth stages under NaCl treatment. Data revealed significant genotypic differences in germination percentage and post-germination survival of seedlings, symptoms of salt injury, changes in the levels of Na(superscript+), Cl(superscript -) and K(superscript +) and total chlorophyll at the vegetative stage, and in pod development, seed yield, and yield components at the reproductive stage. Salinity tolerance in green gram was related to greater final germination and post-germination seedling survival, low scorching, chlorosis and necrosis of aerial parts, reduced Na(superscript +) and Cl(superscript -), slightly enhanced K(superscript +), and greater chlorophyll content. Appearance of increased symptoms on the aerial parts was positively related to increased Na(superscript +) and Cl(superscript -) and negatively to increased K(superscript +). At maturity, pod weight, seed: hull weight ratio, 100-seed weight, seed yield and harvest index were also greater in M-6601. Maintenance of a steady seed: hull weight ratio in M-6601 indicated that a higher seed yield in this genotype is principally due to a greater partitioning of photoassimilates to seed rather than hull during pod development under saline conditions. Based on these criteria, M-6601 and 241/11 were declared salt tolerant and sensitive, respectively. Essentially then, ion-toxicity is the dominant factor modulating the salt tolerance of green gram during growth periods.

Differential Growth, Quality and Nutrient Responses of Azalea Hybrids to Salinity

The azalea hybrids `Delaware Valley White' (`DVW') and `Hershey Red' (`HR') were grown in 7-L containers filled with a 4 sphagnum peat: 2 pine bark: 1 sand medium (v/v) and fertigated for 15 weeks with a complete nutrient solution supplemented with 0, 6 and 12 mm NaCl-CaCl2 (2:1 molar ratio). Regardless of salinity stress, `DVW' plants had dry weights and leaf areas significantly higher (by 24.7% and 10.2%, respectively) than in `HR' plants. Salinity, however, caused differential growth and quality responses between the hybrids. Growth in `DVW' plants decreased with salinity increases, with 22.6% and 32.4% reductions in total dry weight and leaf area, respectively, observed at 12 mm salt compared to controls. Conversely, `HR' plants exposed to 12 mm salt showed no differences in yield parameters with respect to the controls, whereas plants receiving 6 mm salt showed increases of 14.0% and 7.1% in total dry weight and leaf area, respectively, with respect to the controls. Plant quality, as assessed by visual symptoms of salt injury (“salt burn”), was significantly reduced by salinity increases in `DVW' plants, but was not affected in `HR' plants. While unaffected by salinity, leaf K status in `HR' plants was significantly lower than in `DVW', which showed increases in K concentration with salinity increases. Leaf Ca, Cl and Na concentrations increased with added salinity in both hybrids. The `DVW' plants, however, accumulated exceedingly higher Cl and Na concentrations (up to 3.33% and 5,650 mg·L-1 respectively) than in `HR' plants (up to 1.31% and 463 mg·L-1, respectively). Only the yield and quality of `DVW' plants were negatively and significantly correlated to increases in leaf Cl and Na concentrations.