Vertical Distribution of Sodium in Roots of Rice Plants Exposed to Salinity as Analyzed by Cryo Time-of-Flight Secondary Ion Mass Spectrometry

Abstract

Distribution of Na⁺ along the root axis under salinity stress was analyzed in two rice (Oryza sativa L.) cultivars with different salt resistance (salt-sensitive IR 24 and salt-resistant Pokkali). Rice plants were grown hydroponically and NaCl was applied with nutrient solution at concentrations of 0, 25 and 50 mM for 7 d after germination. The distribution of Na⁺ in roots under salinity was analyzed by the cryo time-of-flight secondary ion mass spectrometry (cryo TOF-SIMS). The Na⁺ content in the root was higher in salt-sensitive IR 24 than in salt-resistant Pokkali under NaCl stress. The content was highest at the root tip and was decreased basipetally along the root axis. The difference in Na⁺ content between the cultivars was apparent in all regions from the root tip.     

盐胁迫浓度和胁迫时的温度对水稻耐盐性的影响

 在水培条件下，用5种不同浓度的NaCl溶液对20个水稻品种的3~4叶期幼苗进行盐胁迫处理，10 d后考查不同品种单株盐害级别、苗高、茎叶干重和根系Na[sup]+[/sup]/K[sup]+[/sup]含量比等性状。结果表明，0.5%的NaCl胁迫下，品种间的盐害级别和根系Na[sup]+[/sup]/K[sup]+[/sup]含量比差异最大；0.8%的NaCl胁迫下，品种间的相对苗高和相对茎叶干重差异最大。其中韭菜青、农林72、80 85、洞庭晚籼和丁旭稻为强耐盐水稻品种；Pokkali、IR26、小白芒、勐旺谷、明恢63为耐盐或中度耐盐品种。进一步选择8个耐盐性不同的水稻品种，在3种温度条件下进行苗期耐盐性鉴定，发现在相对低温[昼/夜为(23±3)℃/(15±1)℃\]时，水稻生长缓慢，不同品种的盐害级别和根系Na[sup]+[/sup]/K[sup]+[/sup]含量比均较低；在温度较高[昼/夜为(36±1)℃/(26±2)℃\]时，水稻生长加快，不同品种的盐害级别和根系Na[sup]+[/sup]/K[sup]+[/sup]含量比均增高；只有在适温条件[昼/夜为(30±2)℃/(24±2)℃\]下，水稻生长较快，品种间的盐害级别和根系Na[sup]+[/sup]/K[sup]+[/sup]含量比差别最明显。提出在适温条件下，以0.5%或0.8%的NaCl浓度进行水稻品种耐盐性的筛选和耐盐特性的遗传研究比较合适。     

Genome duplication improves rice root resistance to salt stress

Background

Salinity is a stressful environmental factor that limits the productivity of crop plants, and roots form the major interface between plants and various abiotic stresses. Rice is a salt-sensitive crop and its polyploid shows advantages in terms of stress resistance. The objective of this study was to investigate the effects of genome duplication on rice root resistance to salt stress.

Results

Both diploid rice (HN2026-2x and Nipponbare-2x) and their corresponding tetraploid rice (HN2026-4x and Nipponbare-4x) were cultured in half-strength Murashige and Skoog medium with 150 mM NaCl for 3 and 5 days. Accumulations of proline, soluble sugar, malondialdehyde (MDA), Na⁺ content, H⁺ (proton) flux at root tips, and the microstructure and ultrastructure in rice roots were examined. We found that tetraploid rice showed less root growth inhibition, accumulated higher proline content and lower MDA content, and exhibited a higher frequency of normal epidermal cells than diploid rice. In addition, a protective gap appeared between the cortex and pericycle cells in tetraploid rice. Next, ultrastructural analysis showed that genome duplication improved membrane, organelle, and nuclei stability. Furthermore, Na⁺ in tetraploid rice roots significantly decreased while root tip H⁺ efflux in tetraploid rice significantly increased.

Conclusions

Our results suggest that genome duplication improves root resistance to salt stress, and that enhanced proton transport to the root surface may play a role in reducing Na⁺ entrance into the roots.     

【Short Report】Identification of Chromosome Regions Affecting Leaf Area with Rice Chromosome Segment Substitution Lines

Abstract

The aim of this study was to obtain the information for improvement in source ability via expansion of a flag leaf area in rice (Oryza sativa L.). We identified chromosome regions affecting a trait (CRATs) for leaf area and confirmed their effects with two sets of chromosome segment substitution lines developed from indica landraces Kasalath or Nona Bokra as a donor under japonica cultivar Koshihikari genetic background. We detected 4 and 8 CRATs that increased leaf area by Kasalath and Nona Bokra alleles, respectively. With the Nona Bokra allele, CRAT on chromosome 7 (LA7) increased leaf area by 54% comparing to Koshihikari. LA7 maintained the contents of Rubisco and photosynthetic rate and as a result its “estimated” source ability of a flag leaf was increased by 23%. The effect of LA7 was stable under different environmental conditions, and might be useful for breeding rice with higher source ability and yield.     

小黑麦萌发期耐盐性评价

为了解不同基因型小黑麦萌发期的耐盐能力,以87份小黑麦品种(系)为材料,分析了不同浓度NaCl溶液(100～250mmol·L-1)处理后小黑麦种子萌发的变化。结果表明,200～250mmol·L-1 NaCl对小黑麦种子萌发影响显著。在200mmol·L-1 NaCl胁迫下,可以鉴别不同小黑麦材料的耐盐性差异。利用200mmol·L-1 NaCl胁迫下的发芽势、发芽率、发芽指数、活力指数及幼苗干重的耐盐系数进行聚类分析,87份材料中,耐盐性较强的材料有32份,中间型有14份,盐敏感型41份。     

Growth Responses of Drought Resistant Rice Cultivars to Soil Compaction under Irrigated and Succeeding Non-irrigated Conditions during the Vegetative Stage

Abstract

We investigated whether drought resistant rice cultivars exhibit higher dry-matter production under wet and dry compacted soil conditions in the vegetative stage and determined the dominant factors governing resistance to soil compaction. Three rice cultivars, a drought-sensitive Nipponbare, and drought-resistant Senshou and Dular, were grown in pots at four soil bulk densities (SBD) ranging from 1300 to 1600 dry soil kg m^?3. Root and shoot dry matter productions was slightly smaller in Nipponbare over the 29 days after sowing under irrigated conditions than in the other cultivars at all SBDs. Senshou and Dular also maintained a higher dry matter production, both in relative and absolute values, than Nipponbare under the condition of withheld irrigation from days 29 — 39 after sowing. The higher stomatal conductance and leaf water potential of these two cultivars were supported by a larger root system which was mostly accompanied by lower top-root ratios in the irrigated and compacted soils. The higher plant growth rate under the non-irrigated condition might have been a result of both the higher water absorption rate and water use efficiency, which in turn were supported by the larger root biomass. We conclude that the ability of rice to rapidly develop a root system in the early vegetative phase under compacted soils facilitates plant production under subsequent soil desiccated conditions.     

Characterizing the Saltol Quantitative Trait Locus for Salinity Tolerance in Rice

This study characterized Pokkali-derived quantitative trait loci (QTLs) for seedling stage salinity tolerance in preparation for use in marker-assisted breeding. An analysis of 100 SSR markers on 140 IR29/Pokkali recombinant inbred lines (RILs) confirmed the location of the Saltol QTL on chromosome 1 and identified additional QTLs associated with tolerance. Analysis of a series of backcross lines and near-isogenic lines (NILs) developed to better characterize the effect of the Saltol locus revealed that Saltol mainly acted to control shoot Na⁺/K⁺ homeostasis. Multiple QTLs were required to acquire a high level of tolerance. Unexpectedly, multiple Pokkali alleles at Saltol were detected within the RIL population and between backcross lines, and representative lines were compared with seven Pokkali accessions to better characterize this allelic variation. Thus, while the Saltol locus presents a complex scenario, it provides an opportunity for marker-assisted backcrossing to improve salt tolerance of popular varieties followed by targeting multiple loci through QTL pyramiding for areas with higher salt stress.     

Effects of Salinity Stress on the Seminal Root Tip Ultrastructures of Rice Seedlings (Oryza sativa L.)

Abstract

Growth and structural changes in the seminal root tip of rice seedlings (Oryza sativa L. cv. Nipponbare) in response to NaCl salinity were studied. Seedlings were grown in agar medium with 0, 0.1, 0.3, 1.0, 2.0 and 3.0% NaCl(agar culture), and in water with 0, 0.01, 0.03, 0.06 and 0.1% NaCl (water culture). Seedling growth was significantly suppressed by higher concentrations of NaCl. The effect of NaCl appeared faster in water culture than in agar culture. In both agar and water cultures, root growth was markedly suppressed over shoot growth. Under saline conditions, epidermis, cortex and root cap cells appear to be damaged to a greater extent than the meristem and stelar cells. The most notable ultrastructural change in response to salinity was the development and increment of vacuoles, which seem to provide a space for accumulation of excess ions. Many electron dense deposits were observed in the larger vacuoles of the epidermal and cortical cells. Under saline conditions, cell wall thickening of the epidermis, an increase in endoplasmic reticulum, myelin figures, less compact Golgi bodies and inhibited production of Golgi vesicles were also observed.     

Genetic and physiological analysis of tolerance to acute iron toxicity in rice

Background

Fe toxicity occurs in lowland rice production due to excess ferrous iron (Fe²⁺) formation in reduced soils. To contribute to the breeding for tolerance to Fe toxicity in rice, we determined quantitative trait loci (QTL) by screening two different bi-parental mapping populations under iron pulse stresses (1,000 mg L⁻¹ = 17.9 mM Fe²⁺ for 5 days) in hydroponic solution, followed by experiments with selected lines to determine whether QTLs were associated with iron exclusion (i.e. root based mechanisms), or iron inclusion (i.e. shoot-based mechanisms).

Results

In an IR29/Pokkali F₈ recombinant inbred population, 7 QTLs were detected for leaf bronzing score on chromosome 1, 2, 4, 7 and 12, respectively, individually explaining 9.2-18.7% of the phenotypic variation. Two tolerant recombinant inbred lines carrying putative QTLs were selected for further experiments. Based on Fe uptake into the shoot, the dominant tolerance mechanism of the tolerant line FL510 was determined to be exclusion with its root architecture being conducive to air transport and thus the ability to oxidize Fe²⁺ in rhizosphere. In line FL483, the iron tolerance was related mainly to shoot-based mechanisms (tolerant inclusion mechanism). In a Nipponbare/Kasalath/Nipponbare backcross inbred population, 3 QTLs were mapped on chromosomes 1, 3 and 8, respectively. These QTLs explained 11.6-18.6% of the total phenotypic variation. The effect of QTLs on chromosome 1 and 3 were confirmed by using chromosome segment substitution lines (SL), carrying Kasalath introgressions in the genetic background on Nipponbare. The Fe uptake in shoots of substitution lines suggests that the effect of the QTL on chromosome 1 was associated with shoot tolerance while the QTL on chromosome 3 was associated with iron exclusion.

Conclusion

Tolerance of certain genotypes were classified into shoot- and root- based mechanisms. Comparing our findings with previously reported QTLs for iron toxicity tolerance, we identified co-localization for some QTLs in both pluse and chronic stresses, especially on chromosome 1.     

Genetic diversity and association mapping for salinity tolerance in Bangladeshi rice landraces

Breeding for salinity tolerance using Bangladeshi rice landraces and understand genetic diversity has been limited by the complex and polygenic nature of salt tolerance in rice genotypes. A genetic diversity and association mapping analysis was conducted using 96 germplasm accessions with variable response to salt stress at the seedling stage. These included86 landraces and 10 indica varieties and lines including Nona Bokra, from southern Bangladesh. A total of 220 alleles were detected at 58 Simple Sequence Repeat(SSR) marker loci randomly distributed on all 12 rice chromosomes and 8 Sequence Tagged Site(STS) markers developed for genes SKC1, DST, and SalT. The average gene diversity was 0.5075 and polymorphism information content value was 0.4426, respectively. Cluster analysis revealed that 68 and 21 accessions were clustered into 2 distinct groups, possibly corresponding to indica and japonica groups, respectively and the remaining 7 landraces were classified as an admixed group. In addition to Wn11463, the STS marker for SKC1, RM22418 on Chr. 8 was significantly associated with salinity tolerance, at the location of a QTL detected in previous studies. Our findings of favorable alleles associated with salinity tolerance in Bangladeshi rice landraces, as well as the development of STS markers for salt tolerance genes, will be helpful in future efforts to breed salinity tolerance in rice.     

Antioxidant Capacity and Damages Caused by Salinity Stress in Apical and Basal Regions of Rice Leaf

Abstract

We investigated the mechanisms of increased sensitivity to Na⁺ in the apical and basal regions of the rice leaf under salinity. Three-week-old plants were treated with 200 mM NaCl in hydroponic culture for 3 d. Segments 6 cm in length were obtained from the apical and basal regions of the fully expanded uppermost leaves (6th leaf blades) as old and young tissues, respectively. In the plants exposed to 200 mM NaCl, Nitro blue tetrazolium (NBT) reducing activity, and H₂O₂ and Malondialdehyde (MDA) contents significantly increased, accompanied by the swelling of thylakoids and destruction of thylakoid membranes in the apical regions. However, no indication of oxidative damages was observed in the basal region, even though the Na⁺ content in the basal region was comparable to that in the apical region. In the apical region, the capacity to scavenge H₂O₂ was lower than that in the basal region due to decrease in the constitutive levels of ascorbate peroxidase and guaiacol peroxidase. In addition, the activities of antioxidant enzymes except superoxide dismutase and guaiacol peroxidase decreased drastically after 48 hr of exposure to NaCl. By contrast, the activities of catalase and glutathione reductase in the basal region increased compared with those in the control, and other antioxidant enzymes did not decrease under salinity during the experimental period. These results suggest that the capacity to scavenge reactive oxygen species decreased with age, and thus the apical region of the leaf blade suffered severer damage by Na⁺ than the basal region.     

复合盐胁迫对小麦萌发的影响及耐盐阈值的筛选

为了解Na2SO4和NaCl组成的复合盐对小麦萌发期的胁迫效应,选择5个耐盐性不同的春小麦品种进行复合盐胁迫处理,研究在不同浓度复合盐胁迫下,春小麦品种在发芽势、发芽率、苗高、根数、主根长和苗鲜重等指标上的差异,并采用多重比较和回归分析筛选最适复合盐萌发期处理浓度。结果表明,随着复合盐各盐分浓度升高,小麦萌发期各指标的相对耐盐系数急剧下降,且发芽势、发芽率、苗高、主根长和苗鲜重在不同浓度处理间差异极显著;但复合盐对小麦根数的影响较小,在低盐浓度下差异不显著。在Na2SO4浓度为0.05mol.L-1、NaCl浓度为0.1mol.L-1时,5个品种的发芽率、苗鲜重、苗高的相对耐盐系数在50%左右,发芽势和主根长趋近于30%,同时种子保持较高的活力,可以作为小麦萌发期耐盐鉴定的适宜复合盐胁迫浓度。     

A New Approach to Select Doubled Haploid Rice Lines under Salinity Stress Using Indirect Selection Index

This study determined the indirect selection index of doubled haploid(DH) rice using a multivariate analysis approach to select lines adaptive to salinity stress, comprising three experiments. The first experiment involved the selection of good agronomic characters in a field experiment conducted at an experimental station in Bogor, Indonesia. The second experiment involved salinity tolerance screening through hydroponic cultures using 0 and 120 mmol/L NaCl, conducted at a greenhouse in Bogor. The third experiment involved the validation of the indirect adaptability selection index(IASI) through a field experiment in Sukra(saline area). Field experiments followed a randomized complete block design(RCBD), whereas an RCBD nested factorial design was used for the greenhouse experiment. The first and second experiments used 56 DH lines and four check varieties with three replications. In the second experiment, Pokkali and IR29 varieties were also added as tolerant and sensitive checks of salinity, respectively. The third experiment used 28 selected DH lines, Inpari 29 and one sensitive DH line. The good agronomic index(GAI) was 0.465 yield + 0.433 number of productive tillers + 0.31 number of filled grains. This generated 24 DH rice lines with good agronomic traits. The salinity tolerance index(SaTI) was developed through the average of standardized salinity tolerance score and salinity selection index based on discriminant analysis. This generated 34 DH rice lines with good salinity stress tolerance. The IASI(IASI = GAI – Sa TI) selected 28 DH rice lines adaptive to salinity stress and it was considered effective by Sukra validation.     

The potential of rice to offer solutions for malnutrition and chronic diseases

Elevated Na⁺ levels in agricultural lands are increasingly becoming a serious threat to the world agriculture. Plants suffer osmotic and ionic stress under high salinity due to the salts accumulated at the outside of roots and those accumulated at the inside of the plant cells, respectively. Mechanisms of salinity tolerance in plants have been extensively studied and in the recent years these studies focus on the function of key enzymes and plant morphological traits. Here, we provide an updated overview of salt tolerant mechanisms in glycophytes with a particular interest in rice (Oryza sativa) plants. Protective mechanisms that prevent water loss due to the increased osmotic pressure, the development of Na⁺ toxicity on essential cellular metabolisms, and the movement of ions via the apoplastic pathway (i.e. apoplastic barriers) are described here in detail.     

磷对NaCl胁迫下玉米幼苗渗透调节能力的影响

研究不同供磷水平对NaCl胁迫下玉米幼苗有机渗透调节物质和离子含量的影响。结果表明,盐胁迫下低磷处理玉米幼苗叶片中可溶性糖和游离氨基酸增加,根系中显著降低;增加供磷水平,叶片中可溶性糖和游离氨基酸含量下降,根系中含量上升,同时叶片和根系中可溶性蛋白含量增加。磷可降低盐胁迫下玉米幼苗各器官中的Na~+含量,同时增加各器官的K~+、Ca~(2+)和Mg~(2+)含量,降低Na~+/K~+与Na~+/Ca~(2+)比值。磷有助于维持植株的碳氮代谢平衡,促进有机渗透调节物质的运输与分配,改善各器官的离子平衡,增强植株的渗透调节能力,从而缓解盐胁迫带来的伤害。     

Effects of Exogenous Glycinebetaine on Growth and Ultrastructure of Salt-Stressed Rice Seedlings (Oryza sativa L.)

Abstract

The effects of exogenously applied glycinebetaine on the salt-stress-induced inhibition of growth and ultrastructural damages in rice seedlings were investigated. Glycinebetaine was not effective in alleviating the NaCl-induced inhibition of root growth and rather enhanced the NaCl-induced inhibition. However, it was found to alleviate the inhibition of shoot growth induced by NaCl stress. Concentrations of Na were higher in salt-stressed plants than in unstressed plants. Stressed plants receiving glycinebetaine had a significantly lower Na and higher K concentrations in the shoots than the plants grown without application of glycinebetaine. Salinity induced ultrastructural damages in leaf such as swelling of thylakoids, disintegration of grana stacking and intergranal lamellae and destruction of mitochondria (deficiency of cristae, swelling and vacuolation). Such damages were largely prevented by pretreatment with glycinebetaine resulting in greening of the plants. In roots, the epidermis, cortex and root cap were more sensitive to salt stress than the meristem and stele. The most frequently observed ultrastructural alteration due to NaCl salinity was the formation of many large vacuoles in the root tip and root cap cells. The number of mitochondria was increased and they were aggregated in the cytoplasm of the root tip and root cap cells by treatment with NaCl or NaCl plus glycinebetaine. Glycinebetaine could not prevent the NaCl-induced ultrastructural damages in root cells. The effects of glycinebetaine to mitigate the ultrastructural damages in the chloroplast and mitochondria induced by NaCl might be due to the production of many vacuoles in root cells which may act to store Na and decrease its accumulation in the shoot.     

Yield and growth characteristics of erect panicle type rice (Oryza sativa L.) cultivar,Shennong265 under various crop management practices in Western Japan

Erect panicle rice cultivars utilize solar energy effectively and have improved ecological growing conditions. Among such cultivars, Shennong265 has been grown successfully throughout Northern China. Nevertheless, no studies have yet examined the relationships between crop dry matter productivity, weather conditions, and nitrogen uptake of the erect panicle type rice cultivar in Japan. The objective of our study was to evaluate the productivity of erect panicle rice Shennong265 in Western Japan under varied conditions. Three rice cultivars, Shennong265, Nipponbare, and Takanari were grown in the field under different fertilizer and plant density conditions in Western Japan; using this information, we compared yield and growth characteristics of Shennong265 with those of Nipponbare and Takanari. Although Shennong265 had radiation use efficiency similar to that of the high yielding cultivar (Takanari) and much higher leaf nitrogen content than Takanari and Nipponbare, the average grain yield of Shennong265 grown under normal fertilizer and plant density conditions was approximately 6.9 t ha^?1 as against 6.2 t ha^?1 for Nipponbare and 9.6 t ha^?1 for Takanari. These results suggest that, while Shennong265 has a high yield potential, the environmental conditions including climate, fertilizer, and planting period provided in this study were not suitable for achieving its maximum yield. The reduced performance of Shennong265 may be caused by insufficient fertilizer after heading and by shorter growth periods, as well as by the climate of Western Japan. Additional fertilizer application during the heading stage and earlier transplanting may be needed to obtain higher Shennong265 yields in Western Japan.     

外源硝态氮对高铵胁迫下小麦幼苗生长的影响

为明确外源硝态氮对高铵胁迫下小麦幼苗生长的影响及其生化机理,采用温室水培的方式,以豫麦49(耐高铵品种)和鲁麦15(高铵敏感型品种)为材料,研究了外源硝态氮对高铵胁迫下小麦幼苗形态、激素含量和抗氧化系统的影响。结果表明,高铵胁迫条件下,外源硝态氮显著增加两个小麦品种株高、根长、干重,其中鲁麦15的地上部干重增加量高于豫麦49,而根系干重增加量则表现为豫麦49高于鲁麦15。高铵胁迫下,两个小麦品种植株的IAA、CTK含量、IAA/CTK显著低于对照;外源硝态氮处理5 d后,豫麦49地上部和根系IAA含量、根系CTK含量显著增加,恢复至对照水平;鲁麦15植株虽亦表现显著增加,但仍低于对照。另外,外源硝态氮对高铵胁迫下两个小麦品种地上部和根系的O■释放速率、SOD和POD活性及MDA含量没有显著影响。综上,外源硝态氮缓解小麦幼苗生长高铵胁迫的原因可能是通过增加IAA和CTK合成和转运,影响IAA和CTK之间的平衡,进而达到缓解效果。品种间比较,耐铵型品种豫麦49缓解作用可能源于对地上部和根系IAA含量以及根系CTK含量的协同调控;而高铵敏感型品种鲁麦15的缓解作用可能主要源于对地上部IAA含量的调控。     

盐胁迫下 4 个不同耐盐基因型水稻 Na+ 、K+ 积累效应

选取耐盐性较强的水稻株系‘Fl478’、‘JX99’、‘Pokkali’和盐敏感型品种‘IR29’,设置 6 个 NaCl 浓度梯度处理, 分别为 0、0.1%、0.2%、0.3%、0.4%、0.5%,采用桶栽土培的方法培育至孕穗期,研究盐胁迫对孕穗期水稻植株不同 器官 Na+ 、K+ 分配规律与积累的影响。结果表明：（1）盐胁迫下水稻株系不同器官 Na+ ,K+ 的积累效应存在差异,水稻 株系耐盐性的差异主要表现在根系,而叶鞘对 Na+ 、K+ 的吸收与分配的差异明显。（2）耐盐植株根系聚 Na+ 能力较强, 叶片、叶鞘积累较多的 K+ ,而感盐品种根系积累 K+ 和 Na+ 以缓解根系渗透胁迫,调节根系 Na+ /K+ 平衡稳态,保持水稻 正常的代谢活动。（3）叶鞘是水稻植株关键的 Na+ -K+ 调库,通过吸收和分配 Na+ 来调节根、叶、叶鞘 Na+ /K+ 平衡以提 高水稻耐盐性。（4）耐盐株系叶鞘向叶片选择运输 K+ 的能力、限 Na+ 运输能力强于盐敏感品种,叶鞘对 Na+ 、K+ 吸收 与分配运输能力的大小,决定水稻株系的耐盐性,具体表现耐盐品种叶鞘向吸收与运输 K+ 能力较强、根系限 Na+ 能力 显著高于感盐植株。（5）0.4%~0.5%盐浓度限制水稻叶鞘 Na+ -K+ 库吸收与分配能力,各组织中 Na+ /K+ 失衡,植株耐盐 性降低,受盐害程度加深。（6）盐胁迫促进水稻株系叶鞘向根系吸收较多 Na+ 和向叶片、根系输出 K+ ,却限制 Na+ 对 叶片的分配,保证根系保持较高的 K+ /Na+ ,耐盐幼嫩叶片积累较多的 K+ 以维持叶片组织保卫细胞渗透平衡,保证水稻 植株获得生活必需的光合原料,而盐敏感植株积累的 K+ 主要用于缓解组织渗透胁迫,以维持正常生命活动。     

不同耐性玉米自交系苗期根系对低钾胁迫的生物学响应

通过水培试验,以典型耐低钾玉米自交系90-21-3和低钾敏感玉米自交系835为试材,分别于4、6、7、9和10叶期测定玉米根形态、根系还原力、伤流量和干物质积累量,研究不同耐性玉米自交系苗期根系对低钾胁迫的生物学响应。结果表明,低钾胁迫下,耐低钾玉米自交系90-21-3表现为根长增幅大,根表面积、根体积降幅小,根平均直径降幅大。与低钾敏感玉米自交系835相比,低钾胁迫下耐低钾玉米自交系90-21-3的根系相对发达、根系活力强、伤流量大及干物质积累量较大。