Studies on genome size estimation, chromosome number, gametophyte development and plant morphology of salt-tolerant halophyte Suaeda salsa
Soil salinization and alkalization are among the major agricultural threats that affect crop productivity worldwide, which are increasing day by day with an alarming rate. In recent years, several halophytes have been investigated for their utilization in soil remediation and to decipher the mechanism of salt-tolerance in these high salt tolerant genetic repositories. Suaeda salsa is an annual halophytic herb in the family Amaranthaceae, displaying high salt and alkali-resistance and having nutritive value. However, the fundamental biological characteristics of this valuable plant remain to be elucidated until today.
In this study, we observed the morphology and development of Suaeda salsa, including seed morphology, seed germination, plant morphology, and flower development. Using microscopy, we observed the male and female gametophyte developments of Suaeda salsa. Also, chromosome behaviour during the meiosis of male gametophyte was studied. Eventually, the genome size of Suaeda salsa was estimated through flow cytometry using Arabidopsis as reference.
Our findings suggest that the male and female gametophyte developments of Suaeda salsa are similar to those of the model plant Arabidopsis, and the diploid Suaeda salsa contains nine pairs of chromosomes. The findings also indicate that the haploid genome of Suaeda salsa is approximately 437.5 MB. The observations and results discussed in this study will provide an insight into future research on Suaeda salsa.
KeywordsSoil salinization Suaeda salsa Gametophyte Chromosome Genome
Mega Base pair
Whole-mount-stain clearing laser scanning confocal microscopy
Soil salinization and alkalization have adverse effects on agricultural land, leading to reduced soil fertility. In recent years, salinization and alkalization have emerged as a severe threat affecting crop production worldwide . It is estimated that about 20% of the world’s cultivated land and nearly half of all irrigated land are affected by salinity and alkalinity . The saline-alkaline land is widely distributed in the regions of all major continents, mainly in Eurasia, Africa and the western part of the Americas . China’s cultivatable land is also severely threated by the salinization and alkalization. The total area of saline-alkaline land in China is about 3.6 × 107 ha, accounting for 4.88% of the available land base . The matter is becoming more severe in northeast China, where the saline-alkaline meadow covers more than 70% of the land area . All in all, the severity in the world is still expanding due to human activities and global climate changes .
Suaeda salsa (accepted name: Suaeda maritima subsp. salsa (L.) Soó) is a well-known salt and alkali-resistant, succulent halophyte in the family Amaranthaceae, which was first recorded in an ancient Chinese book “Jiu Huang Ben Cao” that enrolled the potential food plants to cope with famine during Ming dynasty. Suaeda salsa exhibits a high tolerance to salt and alkali stresses and grows very well under salt content more than 0.48% even without salt glands and bladders in its leaves . The most suitable NaCl concentration for promoting its growth is 200 mM, and there is no significant difference can be observed when it is treated with 400 mM NaCl and 10 mM NaCl . As a model salt-tolerant plant, a number of genes involved in salt tolerance such as SsHKT1, SsNHX1, SsCAX1 have been identified, and their functions analyzed [9, 10, 11]. Additionally, Suaeda salsa possesses good Cd, Pb and Mn tolerance and could be considered as a hyperaccumulator for those heavy metals, reflecting its ecological value on recuperating heavy metals-contaminated soil . In addition to the values mentioned above, Suaeda salsa has very high edible and medicinal values as well. It is an annual herb, with excellent palatability for domestic animals and has great value in Chinese traditional medicine . The young leaves and stems of Suaeda salsa are a highly nutritious vegetable that contains abundant proteins, dietary fibre, vitamins, minerals, and flavonoids , The oil from Suaeda salsa seeds is also edible , and it is rich in fatty acids. 90.7% of Suaeda salsa fatty acid is unsaturated. Furthermore, the relative content of unsaturated fatty acids is higher than the other cooking oils, among which, the terephthalic acid, 11-Hexadecenoic acid, and Linoleic acid from Suaeda salsa seeds are up to 0.82, 0.45, 68.74% respectively . It has been documented that the seed oil of Suaeda salsa has the function of decreasing blood sugar and blood pressure, lowering blood cholesterol, developing disease immunity , Therefore, the oil produced from Suaeda salsa seeds is beneficial for human consumption . In this case, biological researchers have been putting the focus on increasing its seed yield .
Considering the scientific and edible values of Suaeda salsa, a number of researches recently have been conducted in the scopes of understanding the salt-tolerance mechanism, medicinal use, and nutrient value [1, 14, 20]. However, the reports regarding the fundamental biological characteristics of Suaeda salsa are limited and not systematic. In this study, the plant and flower morphologies of Suaeda salsa were observed, and the developments of its female and male gametophytes were described. Furthermore, the genomic characteristics of Suaeda salsa concerning chromosome number and genome size were also investigated. These results will improve our understanding of Suaeda salsa for future research and its utilization for crop breeding programme.
Seed morphology and germination of Suaeda salsa
Plant development and morphology of Suaeda salsa
To accurately describe the flower development of Suaeda salsa, we observed the inflorescence stages of Suaeda salsa. According to its flower bud development characteristics, the inflorescence development was divided into five stages. Stage I (100–110 DAG): the flower buds originate from the main stems and branches, and the stamens are invisible (Fig. 3a). Stage II (110–130 DAG): the flower buds grow rapidly, and reach a maximum size, the petals were closely connected, not cracked, and the stigmas were lower than the stamens (Fig. 3b). Stage III (130–140 DAG): the petals begin to split; 1 or 2 stamens are visible. The lengths of stigmas and stamens are the same (Fig. 3c). Stage IV (140–145 DAG): the petals are completely cracked; 5 stamens are naked and light green (Fig. 3d). Stage V (145–155 DAG): the stamens mature, the colour is from light green to yellow, the stigmas are longer than the stamens (Fig. 3e).
We further dissected the flower buds from these five stages and measured the size of the flower organs. As shown in Fig. 3, A-E are the flower buds at five developmental periods, F-J are ovaries at five developmental periods, K-O are stamens at five developmental periods, P-T are petals at five developmental periods. U-Y are calyxes at five developmental periods. The quantification data of different floral parts during these five developmental stages were shown in Additional file 1: Table S1.
Male gametophyte development of Suaeda salsa
Female gametophyte development of Suaeda salsa
Diploid Suaeda salsa has nine pairs of chromosomes
The genome size of Suaeda salsa is approximately 437.5 MB
Salinity and alkalinity are among major stress cues limiting crop growth and productivity. Soil salinization and alkalization have become a global environmental problem that severely affects the sustainability of agriculture. The main reason for the increase in the area of deteriorated land is human activity and climate change . The halophytes are the species withstanding high salt concentrations that kill 99% of other glaucophytes . One type of halophyte, usually dicotyledonous, shows optimal growth at a high NaCl concentration, while the other types of halophytes, generally grow optimally in the absence of salt or at a low NaCl concentration . As the degree of salinization of cultivated land has intensified, researchers are paying more attention to the study of halophytes. According to the statistics, there are about 587 halophytic species in China , among which Suaeda salsa is the most typical one. The growth of Suaeda salsa is significantly stimulated by 200 mM NaCl , showing significant salt-tolerance. Additionally, the nutritive value of Suaeda salsa mentioned above makes it star species attracting the attention of biologists working on salt tolerance improvement of cultivated crops. Recently, several studies on Suaeda salsa have been published focusing on physiology, nutrition, and transcriptome [12, 20, 34]. However, to our knowledge, studies on the fundamental biological characteristics of Suaeda salsa are rarely reported until today.
A seed is an embryonic plant enclosed in a protective outer covering . Yielding seeds have been an important development in the sexual reproduction and the success of gymnosperm and angiosperm plants during the evolution, compared to the primitive plants such as ferns, mosses, and liverworts . The seed of Suaeda salsa is of typical type with a tough seed coat (Fig. 1a, n). This characteristic is an adaption of Suaeda salsa to drought and salinity conditions in the seashore, which could prolong the dormancy and is beneficial for the diffusion prorogation of the species. Seed germination in plants mainly is three types: Hypogeal Germination, Epigeal Germination and, Vivipary (Viviparous Germination). When the Suaeda salsa seeds are germinating, the hypocotyl significantly elongates before the emergence of true leaves and brings the cotyledon above the soil (Fig. 1q-s), showing its epigeal germination type. The model plant Arabidopsis, and most other dicots species such as castor, cotton, papaya, onion also belong to epigeal germination type .
One characteristic of land plants is the alternation of generations, which is also known as metagenesis. Metagenesis is a type of life cycle that occurs in plants and algae in the Archaeplastida and the Heterokontophyta with distinct sexual haploid and asexual diploid stages . Liverworts, mosses, and hornworts are gametophyte-dominant, while the seedless vascular plants and angiosperms are sporophyte-dominant. Suaeda salsa gametophyte is much reduced to the minimum of several cells and relies on sporophyte to obtain nutrition . The haploid female and male gametophytes are essential reproductive units of flowering plants . Male gametophyte development begins with the division of a sporophyte cell. In this study, we described the male gametophyte development of Suaeda salsa with five developmental stages, from microspore mother cell to mature pollen containing three cells (Fig. 4). Since two sperms have already formed in the mature pollen grains, the development of male gametophyte of Suaeda salsa belongs to the minority type, which is represented in ~ 30% of plants. The mature pollen grain of majority plants (~ 70%, for instance, plants from Solanaceae and Liliaceae) contains only two cells, one vegetative and one generative, and the latter one undergoes the second mitosis just after pollen germination, giving rise to two sperms required for double fertilization . The female gametophyte is a unique structure comprised of quite a few cells and contains the sexual cells . A well-developed female gametophyte is the basis of plant reproduction. Generally, more than 15 different patterns of female gametophyte have been described in angiosperms, which could be classified into three major types: Monosporic (Polygonum) type, Bishopric (Alisma) type, and Tetrasporic (Drusa) type . Although the mature pollen morphology has been reported a decade ago , this is the first time to observe and describe the male gametophyte development in Suaeda salsa.
The observation of the female gametophyte development of Suaeda salsa is challenging. At first, we attempted to reveal its development process through DIC microscopy. However, the experimental results indicated that this method is not quite effective because the complete development process cannot be observed due to the dense embryo sac structure. Partial development stages of female gametophyte development were shown in Additional file 5: Figure S3. We also tried the method of resin section. Unfortunately, we could either not obtain a set of images shown the complete development process of female gametophyte development of Suadea salsa (Additional file 6: Figure S4), probably due to the thin oval wall and the limited number of generative cells in one ovule. Eventually, taking advantage of WCLSM (Whole-mount-stain clearing laser scanning confocal microscopy) technology, we successfully observed the development process of the female gametophyte of Suaeda salsa. The observations support that the female gametophyte development pattern of Suaeda salsa belongs to Polygonum type (Fig. 5). It has been reported that the plants from family of Brassicaceae (e.g., Arabidopsis, Capsella, Brassica), Gramineae (e.g., maize, rice, wheat), Malvaceae (e.g., cotton), Leguminoseae (e.g., beans, soybean), and Solanaceae (e.g., pepper, tobacco, tomato, potato, petunia) [42, 43, 44, 45]) showed Polygonum type female gametophyte development. The observation in this study provides a new example from family Amaranthaceae, which also adopts the Polygonum development type of female gametophyte. The healthy development of the male and female gametophytes and the successful completion of the double fertilization directly determine the seed yield. Suaeda salsa, as an excellent potential oil crop, scientists nowadays are trying to increase its yield. Here, we revealed the developmental types of male and female gametophytes, which would lay an important foundation for molecular breeding of Suaeda salsa.
The chromosome is the vector of genetic information in eukaryotes, it is a combination of Deoxyribonucleic acid (DNA) and protein molecules with part or all of the genetic material of an organism. Typically, the number of chromosomes is constant for all individuals of a specific species, and this is of great importance in determining the phylogeny and taxonomy of the species . Genome is the sum of total genetic material in the haploid set of chromosomes. For most angiosperms, the somatic cell of sporophyte contains two haploid sets of genomes, while the generative cell of gametophyte only has one set. Even though several databases are focusing on the chromosome number and genome size, the extensive observation and investigation on the chromosome number and genome size of specific species are still imperative and of great significance. The chromosome number of Suaeda salsa has been reported in the 1950s and 1960s [41, 47]. In the Chromosome Count Database (http://ccdb.tau.ac.il/home/), 16 Chromosome number records of this species (Accepted name: Suaeda maritima subsp. salsa (L.) Soó) were deposited with the 2n = 18, 36, 54, respectively (Additional file 2: Table S2) . The inconsistency on chromosome counts records of this species is probably due to the different ecotypes that were investigated. Most of the records have 36 or 54 chromosomes were from Siberia area [48, 49, 50, 51, 52]. To confirm this significant characteristic of Suaeda salsa of our ecotype, we observed its chromosome behaviour during male gametogenesis. Our results showed that the chromosome number of Suaeda salsa is 2n = 18 (Fig. 6). It has been reported that most of the species form Chenopodiaceae have relatively stable chromosome organization with the basic number of 9. The exceptions are Camphorosma and Spinacia, whose basic chromosome numbers are 6. Our observation is consistent with this conclusion . Taken together, we can speculate that X = 9 might be the original basic chromosome number of Dianthus order. Moreover, the estimated genome size of Suaeda salsa haploid is approximately 437.5 ± 28.96 MB through flow cytometry in this study (Fig. 7). The results from chromosome number observation and genome size estimation provide useful information for the genomic research on Suaeda salsa.
In this study we observed the seed, plant and floral organ morphology and development of Suaeda salsa, the results indicating that the seed germination pattern of Suaeda salsa belongs to epigeal germination, and the developments of both male and female gametophytes of Suaeda salsa are similar to those of model plant Arabidopsis. The chromosome number of Suaeda salsa is 2n = 19. The genome size of Suaeda salsa is approximately 437.5 MB estimated by FCM. The observations and results discussed in this article will provide us with a better understanding of the salt (stress)-tolerant plant and insights into future research on Suaeda salsa.
Plant materials and growth conditions
Suaeda salsa seeds were provided by Yancheng Lvyuan Salt Soil Agricultural Technology Co. Ltd., Yancheng, Jiangsu, Southeast China (http://www.ychpz.com/index.asp). Seeds were treated with 0.03% Gibberellin and planted at 25 °C in the greenhouse with 16/8 h of light-dark photoperiod cycle. The Suaeda salsa plants growing in the greenhouse are flowering during summer. The wild-type Arabidopsis thaliana (L.) Heynh (Col-0; CS60000) was obtained from the Arabidopsis Biological Resource Center (Columbus, OH, USA; https://abrc.osu.edu/). Arabidopsis plants were grown in a greenhouse with 60% humidity under a 16 h light/8 h dark photoperiod cycle at 22 °C. Flower buds of different developmental stages were used from matured plants for observation of male and female gametophyte development.
Plant morphology observation and measurement
The photographs showing the plant morphology of Suaeda salsa were taken at 10, 20, 40, 80,100 days after germination (DAG). The leaves and lateral stems of Suaeda salsa from 100 DAG were dissected and photographed using a Nikon D7200 digital camera. The flower buds at different developmental stages were picked up with a tweezer. The floral organs were dissected with 0.1 mm syringes under an anatomical microscope and then placed on agar plates (0.8%) for photographing. The images were taken through a Leica DFC550 microscope, and the measurements were performed using ImageJ software (NIH).
Observation of male gametophyte development
Male gametophyte development was observed by both differential interference contrast (DIC) microscopy and inflorescence microscopy. For DIC microscopy, the pollens of different development stages were obtained and cleared by chloral hydrate solution (chloral hydrate: H2O: glycerol = 8: 2: 1) on slides. Cleared anthers were imaged using a BX63 microscope (Olympus) with DIC optics. For inflorescence microscopy, the samples were decoloured in 25% acetic acid 75% ethanol solution for three times and stained with 4′, 6-Diamidino-2-Phenylindole (DAPI), following the method described by Yang et al. (2009) and Dou et al. (2011) [54, 55]. The nuclei of male gametophytes were then observed under Leica MZ10F and DM2500 microscopes.
Observation of female gametophyte development
The flower buds at different developmental stages were collected and fixed in FAA solution (50% ethanol: glacial acetic acid: formaldehyde =89:6:5) for 24 h. The samples were then washed with 50% ethanol twice and transferred into 70% ethanol for storage. The ovaries were dissected from the fixed florets under a dissecting microscope. WCLSM (Whole-mount-stain clearing laser scanning confocal microscopy) theology [56, 57] was applied to observe the female gametophyte development of Suaeda salsa. The dissected ovaries were hydrated sequentially in 50% ethanol, 30% ethanol and distilled water, and mordanted in 2% aluminum potassium sulphate for 20 min followed by staining with eosin (10 mg/L in 4% sucrose solution) for 10–12 h. The stained samples were then retreated with 2% aluminum potassium sulphate for 20 min to remove the dye from the wall of the ovaries. After three times of rinsing with distilled water, the samples were treated successively with 30, 50, 70, 90 and 100% ethanol for 20 min each for dehydration. For cleansing, the dehydrated samples were treated in ethanol-methyl salicylate solution (V: V = 1:1) for 2 h, and then kept in methyl salicylate solution for at least 2 h. The cleansed samples were placed on concavity slides and mounted with fingernail polish and photographed under a Leica SP8 Laser scanning confocal following the reported method .
Chromosome number analysis
The pollen grains with 0.3–0.5 mm in diameter were collected and used for chromosome number observation. The chromosome spreads of microsporophytes were prepared as described previously by  and stained with 1.5 μg/ml 4,6-diamidino-2-phenylindole (DAPI). Images of chromosome spreads were taken using a Zeiss (Model) microscope.
Genome size estimation by FCM
Since Arabidopsis thaliana has been sequenced, and its genome size is known (n = 125 MB, The Arabidopsis genome initiative, 2000) , it was selected as reference in this analysis. The fresh leaves of tested species were dissected from the plants and chopped by a very sharp razor blade in 1 ml Arumuganathan and Earle Buffer . The suspension was then filtered through a 30 μm mesh and 1:100 DAPI (10 mg/ml) was added for nuclei staining. The sample was left for at least 5 min before being analyzed using MoFlo XDP Sorter (Beckman). Typically, 4000–5000 nuclei were measured in each run. The inflorescence strength of different peaks of the Arabidopsis and Suaeda salsa were recorded by the instruments and the C- values for different peaks of DNA histogram were generated by the Beckman software. The inflorescence strength of the 2C peak was used for estimating the genome size of Suaeda salsa .
We thank Chunyin Zhang for providing the original seeds of Suaeda salsa.
YC. and YQ. initiated and designed the research. YC, PY, LZ, SP, QZ, Zeyun-L, and JL performed the experiments. WL, JX, Zhibin-L, Li-L, and XH analyzed the data. HZ, GL, JM, and Lei-L helped with a critical discussion on the work. YC and PY wrote the paper. YQ and MA revised the paper. All authors discussed the results and approved the final version of the manuscript.
Y.Q. is supported by a grand from National Science Foundation, China (U1065212) and Guangxi Distinguished Experts Fellowship. Y.C. is supported by a grant from National Science Foundation, China (31671267), a grant from state key laboratory of Ecological Pest Control for Fujian and Taiwan Crops (SKB201708), and a grant from Natural Science Foundation of Fujian Province (2018 J01704). The Funding bodies were not involved in the design of the study and collection, analysis, and interpretation of data and in writing the manuscript.
Ethics approval and consent to participate
Consent for publication
The authors declare that they have no competing interests.
- 1.Yu Y, Huang WG, Chen HY, Wu GW, Yuan HM, Song XX, Kang QH, Zhao DS, Jiang WD, Liu Y, Wu JZ, Cheng LL, Yao YB, Guan FG. Identification of differentially expressed genes in flax (Linum usitatissimum L) under saline-alkaline stress by digital gene expression. Gene. 2014;549(1):113–22.PubMedCrossRefGoogle Scholar
- 3.Wang ZQ. Salt-affected soil in China. Beijing: Science Press; 1993. [in Chinese]Google Scholar
- 4.Wang JL, Huang XJ, Zhong TY, Chen ZG. Review on sustainable utilization of salt-affected land. Acta Geograph Sin. 2011;66(5):673–84.Google Scholar
- 5.Kawanabe S, Zhu T. Degeneration and conservation of Aneurolepidium. Chinense grassland in northern China. J Jpn Grassland Sci. 1991;37:91–9.Google Scholar
- 9.Shao Q, Han N, Ding TL, Wang BS. Polyclonal antibody preparation and expression analysis of high-affinity K+ transporter SsHKT1. J Wuhan Bot Res. 2006;24:292–7.Google Scholar
- 12.Zhang X, Li M, Yang H, Li X, Cui Z. Physiological responses of Suaeda glauca and Arabidopsis thaliana in phytoremediation of heavy metals. Environ Manag. 2018;223:132–9.Google Scholar
- 13.Sun JJ, Wang RH, Dai HL, Zhang BW, Dai YC. Research progress on the chemical constituents of Suaeda salsa (L.) and their development and utilization. Shandong Chem Ind. 2018;47:71–2.Google Scholar
- 14.Zhao HL. Study on edible value of Suaeda salsa (l.) pall. J Anhui Agr Sci. 2010;38:14350–1.Google Scholar
- 15.Zhang LB, Xu HL, Zhao GS. Salt tolerance of Suaeda salsa and its soil ameliorating effect on coastal saline soil. Soils. 2007;39:310–3.Google Scholar
- 16.Gu FT. Research in exploiting the green series of edibles-Suaeda Salsa. J Binzhou Edu College. 1999;5:43–8.Google Scholar
- 17.Ding HR, Hong Z, Yang ZQ, Wang MW, Wang K, Zhu XM. Progress of study on halophyte Suaeda salsa. Acta Agr Jiangxi. 2008;20:35–7.Google Scholar
- 18.Li HS, Fan YX. Extraction and characteristics analysis of Suaeda salsa seed oil. China Oils Fats. 2010;35:74–6.Google Scholar
- 19.Shao QL, Xie XD, Zhang FS, Cui HW, Cao ZY. A preliminary study on the artificial cultivation and breeding selection of Suaeda salsa. Chinese J Eco-Agri. 2004;12(1):47–9.Google Scholar
- 20.Shi HQ, Jiang W, Yi D, Liu FY, Yi GY. Study on the preparation of conjugated linoleic acid with S. salsa seed oil and the determination of molecule structures. Food Sci. 2005;26(5):80–4.Google Scholar
- 27.Zhang J, Chen QQ, Zhao X, Wei N. Karyotype analysis and pollen mother cell meiosis observation in taraxacum antungense kitag (asteraceae). Acta Bot Boreali-Occidentalia Sin. 2012;32(12):2419–24.Google Scholar
- 30.Wang YP, Xiao BY, Xiong WB, Wu SD, Ji AJ, Duan LX. Genome size analysis for Morinda officinalis how using flow cytometry. Trad Chinese Drug Res Clini Pha. 2018;29:657–60.Google Scholar
- 35.Skinner DJ, Sundaresan V. Recent advances in understanding female gametophyte development. F1000. 2018;7:F1000 Faculty Rev-804. Published 2018 Jun 20. https://doi.org/10.12688/f1000research.14508.1.
- 36.Li W, Ma H. Gametophyte development. Curr Biol. 2002;12(21):718–21.Google Scholar
- 38.Ahmed S, Cock MJ, Pessia E, Luthringer R, Cormier A, Robuchon M, Sterck L, Peters AF, Dittami SM, Corre E, Valero M, Aury JM, Roze D, Peer YV, Bothwell J, Marais GA, Coelho SM. A haploid system of sex determination in the brown alga ectocarpus sp. Curr Biol. 2014;24(17):1945–57.PubMedCrossRefGoogle Scholar
- 39.Chehregani A, Malayeri B, Yousefi N. Developmental stages of ovule and megagametophyte in Chenopodium botrys L (Chenopodiaceae). Turk J Bot. 2009;33(2):75–81.Google Scholar
- 41.Darlington CD, Wylie AP. Chromosome atlas of flowering plants. Kew Bull. 1956;11(2):37.Google Scholar
- 43.Willemse MTM, Van WJL. The female gametophyte. In: Johri BM, editor. Embryology of angiosperms. Heidelberg: Springer, Berlin; 1984.Google Scholar
- 44.Huang BQ, Pierson ES, Russell SD, Tiezzi A, Cresti M. Video microscopic observations of living, isolated embryo sacs of Nicotiana and their component cells. Sex Plant Reprod. 1992;5(2):156–62.Google Scholar
- 47.Federov AA. Chromosome numbers of flowering plants. Hereditas. 1974;63(1):328–32.Google Scholar
- 49.Lomonosova MN, Krasnikov AA, Krasnikova SA. Chromosome numbers of Chenopodiaceae from Siberia. Bot Žhurn. 2001;86(9):145–6.Google Scholar
- 50.Lomonosova MN, Krasnikov AA, Krasnikova SA. Chromosome numbers of Chenopodiaceae family members of the Kazakhstan flora. Bot Žhurn. 2003;88(2):134–5.Google Scholar
- 51.Lomonosova MN. Chromosome numbers of Chenopodiaceae species from Russia and Kazakhstan. Bot Žhurn. 2005;90(7):1132–4.Google Scholar
- 52.Lomonosova MN. Chromosome numbers of some Chenopodiaceae representatives of the flora of Russia. Bot Žhurn. 2006;91(11):1757–9.Google Scholar
- 53.Zhang F, Yao Y. Karyotype analysis of Suaeda salsa (L) pall. Shandong Sci. 2013;26:53–5.Google Scholar
- 54.Yang K, Xia C, Liu X, Dou X, Wang W, Chen L, Zhang X, Xie L, He L, Ma X. A mutation in Thermosensitive male sterile 1, encoding a heat shock protein with DnaJ and PDI domains, leads to thermosensitive gametophytic male sterility in Arabidopsis. Plant J. 2009;57(5):870–82.PubMedCrossRefGoogle Scholar
- 56.Zhang HH, Feng JH, Lu YG, Yang BY, Liu XD. Observation on formation and development of autotetraploid rice embryo sac using laser scanning confocal microscope. Chinese Elec Micro Socie. 2003;22:380–4.Google Scholar
- 57.Liu XD, Lu YG, Zhu HL, Xu XB, Feng JH, Xu SX. Abnormal behavior of nuclei and microtubule (MT) organizational changes during embryo sac development in the poly-egg mutant, AP IV of rice. Acta Bot Sin. 2004;46:829–38.Google Scholar
- 60.The Arabidopsis Genome Initiative. Analysis of the genome sequence of the flowering plant Arabidopsis thaliana. Nature. 2000;408 (6814):796.Google Scholar
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