EditorialEditorial

J. POSPÍŠILOVÁ

Biologia plantarum 64: 2020

Cadmium and zinc uptake and translocation in dwarf Polish wheat seedlings as affected by calcium and potassium combinationOriginal Papers

W. SHUAI, Q. YAO, X. CHEN, Y. CHENG, X. XIAO, J. ZENG, X. FAN, H. KANG, L. SHA, H. ZHANG, Y. ZHOU, Y. WANG

Biologia plantarum 64: 642-652, 2020 | DOI: 10.32615/bp.2019.162

Combination of calcium and potassium (Ca-K) influences cadmium and zinc uptake and translocation in dwarf Polish wheat (Triticum polonicum), but its effects remain unclear. In the present study, a high concentration of Ca-K reduced uptake of Cd and Zn by roots and promoted their translocations to shoots under Cd and Zn excess. Whatever under a low or high concentration of Ca-K, Zn inhibited Cd uptake and translocation under Cd+Zn stress when compared with Cd stress alone. However, the reduced Cd content caused by Zn under the high concentration of Ca-K was significantly lower than under the low concentration of Ca-K. Under both Ca-K treatments,...

Flag leaf vein traits and their correlation with photosynthesis and grain yield in wheat genotypes of differing ploidyOriginal Papers

H.M. XU, Y.L. CHEN, Y.Y. LI

Biologia plantarum 64: 633-641, 2020 | DOI: 10.32615/bp.2020.092

Leaf venation and coupled physiological function of wild plants co-evolve during the natural selection. How artificial selection affects leaf vein traits and coordinated physiological functions of main crops are largely unknown. This study examined the changes of leaf vein traits and their correlation with gas exchange of flag leaves and yield in eight wheat genotypes of differing ploidy under the same growing conditions. The results indicate that flag leaf vein density (VLA), major-vein density (VLA_major), and minor-vein density (VLA_minor) decreased whereas the proportion of minor-vein length and interveinal distance between...

The role of gasotransmitters in movement of stomata: mechanisms of action and importance for plant immunitySpecial Issue: Gasotransmitters

S. GAHIR, P. BHARATH, A.S. RAGHAVENDRA

Biologia plantarum 64: 623-632, 2020 | DOI: 10.32615/bp.2020.071

Stomatal guard cells are specialized epidermal cells regulating gas exchange. The ability to open or close in response to external and internal cues makes stomata a dynamic and fascinating system. Stomatal closure upon infection ensures restriction of pathogen entry into the plant and forms an essential component of innate immunity. The opening or closure of stomata is dependent on the turgidity or flaccidity of guard cells, respectively, facilitated by several signaling components, including reactive oxygen species, nitric oxide (NO) and Ca²⁺. Among these, NO is the most extensively studied gasotransmitter. Its pivotal role in stomatal...

Lower photosynthetic capacity under higher spectral reflectance? The case of Actinidia polygamaOriginal Papers

Z.-X. WANG, G.-L. SHI, L. CHEN, D. SUN, P.-L. Xu, H.-Y. Qin, J. AI

Biologia plantarum 64: 616-622, 2020 | DOI: 10.32615/bp.2020.083

The variegated leaves of Actinidia polygama exhibit a striking colour change during development. However, little is known whether the photosynthetic capacity of white leaves can be maintained. Therefore, spectrum properties, leaf structure, net photosynthetic rate (P_N), and chlorophyll fluorescence in the green and white leaves were investigated. Although reflectance at 400 - 700 nm in white leaves was higher than that in green leaves, total chlorophyll content of white leaves was similar to that in green leaves. Palisade tissue cells of white leaves contained functional chloroplasts. Large intercellular spaces were observed between...

Exogenous melatonin enhances salt stress tolerance in tomato seedlingsOriginal Papers

M.A. ALTAF, R. SHAHID, M.X. REN, S. NAZ, M.M. ALTAF, A. QADIR, M. ANWAR, A. SHAKOOR, F. HAYAT

Biologia plantarum 64: 604-615, 2020 | DOI: 10.32615/bp.2020.090

Melatonin (N-acetyl-5-methoxytryptamine) is an essential molecule which regulates plant growth and development and alleviates the damaging effects of abiotic stresses. To evaluate the important functions of melatonin in response to salinity stress, the effects of exogenous melatonin on the antioxidant system and growth of tomato (Solanum lycopersicum L.) under 150 mM NaCl stress were investigated. The application of 100 μM melatonin compensated the growth inhibition caused by salt-stress. Melatonin treated seedlings had an increased fresh and dry masses of shoots and roots. The application of 1 - 200 µM melatonin notably enhanced the...

Cytogenetic insights into FestuloliumSpecial Issue: Festulolium

J. MAJKA, M. MAJKA, D. KOPECKÝ, J. DOLEŽEL

Biologia plantarum 64: 598-603, 2020 | DOI: 10.32615/bp.2020.095

Climate change calls for new methods and plant materials to breed crops adapted to new environmental conditions. Sustainable forage and amenity grass production during periods of severe drought and heat waves during summer, and unequal distribution of precipitation over the year will require drought-tolerant genotypes. However, high-yielding ryegrasses (Lolium spp.), which are the most commonly used grass species, suffer during abiotic stresses. Introgression of drought and heat tolerance from closely related fescues (Festuca spp.) offers an opportunity to develop superior hybrid cultivars to mitigate the negative impact of climate change....

The toxicity of BDE-47 to the photosystem of Lemna minor frondsOriginal Papers

N.W. QIU, W.R. ZHANG, X.H. YAN, R.J. WANG, L. TIAN, G.L. HAN, F. ZHOU

Biologia plantarum 64: 591-597, 2020 | DOI: 10.32615/bp.2020.091

To elucidate the toxicity of 2,2ʹ,4,4ʹ-tetrabromodiphenyl ether (BDE-47) on photosynthetic primary processes, in vivo and in vitro treatments of BDE-47 were performed. The 20-d treatment in vivo (5 - 20 μg dm^-3) suppressed the reproduction of duckweed (Lemna minor) and led to decline in chlorophyll (Chl) content of fronds. The most obvious features of BDE-47-treated fronds included a Chl a fluorescence rise at the J phase and a depression at the G phase, whereas significant fluorescence rises at the L, K, and J phases were found on the ΔV_t curve of thylakoid membranes treated...

Festulolium, a century of research and breeding and its increased relevance in meeting the requirements for multifunctional grassland agricultureSpecial Issue: Festulolium

M.W. HUMPHREYS, Z. ZWIERZYKOWSKI

Biologia plantarum 64: 578-590, 2020 | DOI: 10.32615/bp.2020.108

Festulolium are grasses formed through interspecific hybridisation of ryegrass (Lolium) and fescue (Festuca) species. The Lolium-Festuca genome complex represents a vast array of heterogeneous and largely outbreeding grass species that have evolved, diverged, and adapted, allowing their world-wide colonisation of temperate grasslands. While strategies for grass improvement have focused primarily on intraspecific breeding and, in particular, on the agronomically desirable species Lolium perenne and Lolium multiflorum, a growing interest has emerged in interspecific hybrids as alternatives. The principal driver has...

Comparative metabolomic profiling in the roots of salt-tolerant and salt-intolerant maize cultivars treated with NaCl stressOriginal Papers

J.Y. YUE, L.H. WANG, X.T. DOU, Y.J. WANG, H.Z. WANG

Biologia plantarum 64: 569-577, 2020 | DOI: 10.32615/bp.2020.082

Maize crops are sensitive to NaCl stress, which is one of the most harmful abiotic stresses affecting agricultural productivity. To gain further insights into the differential metabolic responses to NaCl stress, we employed metabolomics and physiological approaches to understand the response of salt-tolerant (PH6WC) and sensitive (PH4CV) cultivars of maize. Salt stress caused a significant reduction in root growth, lower root numbers, softened roots, leaf etiolation, inhibition of leaf formation, and decreased shoot height and stem width in both the tolerant and sensitive genotypes compared with the control. These morphological characteristics increased...

Drought tolerance and regrowth capacity revealed in the Festuca-Lolium complexSpecial Issue: Festulolium

V. CERNOCH, D. KOPECKY

Biologia plantarum 64: 561-568, 2020 | DOI: 10.32615/bp.2020.093

The climate change appears to have accelerated in recent years, and more changes are envisaged in the near future. With this in mind, breeders should consider the choices of materials to be used in breeding for the future to potentially mitigate the impacts of changes. In forage grasses, a special attention has to be paid to drought and heat tolerance. Here, in a screening trial of numerous accessions, we investigated drought tolerance and after-drought recovery rates among the species of the Festuca-Lolium complex, including cultivars and breeding materials as well as various ecotypes of wild species. Experimental trials were done using rainout...

Genes for defense response to Plasmodiophora brassicae during late infection in small spheroid galls of Brassica rapaOriginal Papers

H. YANG, X.Y. FANG, X.L. WANG, J. ZHENG, C.L. YI, J. FAN, S. YUAN, J. SHANG, I.Y. HUANG, W.M. WANG

Biologia plantarum 64: 551-560, 2020 | DOI: 10.32615/bp.2020.024

Plasmodiophora brassicae is a biotrophic pathogen causing clubroots of cruciferous crops. The Brassica rapa accession T1-145 has an ability to produce small spheroid galls (SSGs), which represent neither a fully compatible interaction nor a complete resistance. To explore the defense response in SSGs induced by P. brassicae infection, global transcriptome profiling SSGs was performed at different time points. By comparing gene expression patterns, we identified many defense related genes. The first group included genes encoding receptor-like protein/kinases, such as cysteine-rich receptor-like protein kinases, receptor-like...

MicroRNA profiling the resurrection plant Haberlea rhodopensis unveils essential regulators of survival under severe droughtOriginal Papers

E. APOSTOLOVA, M. GOZMANOVA, L. NACHEVA, Z. IVANOVA, V. TONEVA, I. MINKOV, V. BAEV, G. YAHUBYAN

Biologia plantarum 64: 541-550, 2020 | DOI: 10.32615/bp.2020.062

Small RNAs (sRNAs) are essential components of gene-regulatory networks, which guide plant development and tune it to environmental challenges. Though the past years have witnessed evidences on sRNA importance for stress response, there is scarce data on their involvement in resurrection plant survival under severe drought. Haberlea rhodopensis (hrh) is an angiosperm resurrection species, whose vegetative tissues can tolerate desiccation and recover upon rehydration. In this study, high-throughput sequencing sRNAs indicated a higher complexity of the sRNA population, especially of a 24 nt sRNA category, in the desiccated vegetative tissue of...

Evaluation of two promoters for generating transgenic potato plants as salicylic acid biosensorsOriginal Papers

H.M. ABD EL-HALIM, I.M. ISMAIL, N.M. AL ABOUD, D. ELGHAREEB, E.A. METRY, A.F. HOSSIEN, E.M. FAHMY

Biologia plantarum 64: 535-540, 2020 | DOI: 10.32615/bp.2020.067

Plants are severely affected by many biotic stresses, which cause a reduction in crop quality and quantity. One of the strategies to manage biotic stresses is the generation of transgenic plant lines that can be used as biosensors. These biosensor plants can trigger an early warning upon any pathogen infection. Two promoters with β-glucuronidase reporter gene fusions were constructed. The first contained the flagellin sensing 2 gene promoter, whereas the second contained synthetic promoter containing four repeats of cis-acting elements from the pathogen-related protein 1 gene and two transcription enhancers from the...

A rapid translocation of photoassimilates from source organs maintains grain yield in cowpea subjected to drought stress during grain fillingOriginal Papers

C. EGASHIRA, Y. HASHIGUCHI, E. KURAUCHI, Y. TATSUMI, A.C.S. NAKAGAWA, N. HAMAOKA, T. YUASA, M. IWAYA-INOUE, Y. ISHIBASHI

Biologia plantarum 64: 529-534, 2020 | DOI: 10.32615/bp.2019.129

We examined the influence of drought stress during grain filling on grain yield to investigate changes in assimilates in sink and source organs. When plants were subjected to drought stress from the start of grain filling until harvest, the photosynthetic rate rapidly decreased. Grain dry mass during maturation was not significantly different between the control and drought-stressed plants. Under drought stress conditions, starch content in source organs (peduncle, leaf, petiole, stem, and root) was significantly lower than in corresponding organs of control plants; the greatest difference was seen in leaves. Consistent with this observation, α-...

Different responses of the halophyte Carex pumila to salt stressOriginal Papers

S.W. WANG, F.F. XU, L.J. GUO, T.T. HE, X.L. LI, L. YUAN, Q.F. WANG, H.T. LIU

Biologia plantarum 64: 519-528, 2020 | DOI: 10.32615/bp.2020.075

Salt stress is one of the most important stresses that affect coastal vegetation. A halophyte Carex pumila plays a crucial role in the maintenance of fragile ecosystems in coastal areas. Thus, understanding the mechanism of C. pumila responses to salt stress is a prerequisite for the conservation and utilization of this species. After treatment with 200, 300, 400, 500 mM NaCl for 60 h, C. pumila leaves displayed a decline in the relative water content and an increase in salt injury index. Osmolyte accumulation, as a function of osmotic adjustment, and antioxidant enzyme activities were maintained under salinity, even at a high...

Nitric oxide mediated mechanisms adopted by plants to cope with salinitySpecial Issue: Gasotransmitters

A. SHARMA, D. KAPOOR, J. WANG, M. LANDI, B. ZHENG, D. YAN, H. YUAN

Biologia plantarum 64: 512-518, 2020 | DOI: 10.32615/bp.2020.070

Worldwide, a relevant surface of arable lands is facing salt stress, and this surface is increasing continuously due to both natural and anthropogenic activities. Nitric oxide (NO) is a small, gaseous molecule with a plethora of physiological roles in plants. In addition to its normal physiological functions, NO protects plants subjected to different environmental cues including salinity. For example, NO mediates photosynthesis and stomatal conductance, stimulates the activity of Na⁺/H⁺ antiport in tonoplast, promotes the biosynthesis of osmolytes, and counteracts overaccumulation of reactive oxygen species in plant cells under...

Comprehensive transcriptome analyses of different Crocus flower tissues uncover genes involved in crocin biosynthesisOriginal Papers

H.M. SHU, S.Q. GUO, W.C. NI

Biologia plantarum 64: 504-511, 2020 | DOI: 10.32615/bp.2020.068

The stigma of Crocus sativus is used in traditional Chinese medicine and has drawn attention as a rich source of crocin, a compound with a reported activity that counters various cancers, depression, and cardiovascular diseases. However, our knowledge of crocin biosynthesis in Crocus is still limited. To identify the genes that encode key enzymes responsible for crocin production, transcriptome analyses of Crocus stigma, petal, and stamen were performed. There were 109 136 unigenes in the three Crocus flower tissues: 10 862 unigenes were expressed explicitly in stigmas. A total of 469 and 335 down-regulated differentially...

Mechanisms of drought resistance in introgression forms of Lolium multiflorum/Festuca arundinaceaSpecial Issue: Festulolium

D. PERLIKOWSKI, A. KOSMALA

Biologia plantarum 64: 497-503, 2020 | DOI: 10.32615/bp.2020.076

Drought resistance in plants can be associated with four different strategies to cope with water stress. These strategies are classified as drought escape, avoidance, tolerance, and recovery. The expression of each strategy depends on plant species and its genetic potential, but also on the environmental conditions, including the stress intensity and duration. Often, prolonged drought conditions are associated with drought escape or avoidance, whereas short but severe drought periods induce drought tolerance. To analyze the components of drought resistance in forage grasses, we applied two Lolium multiflorum/Festuca arundinacea introgression...

Successful generation of anti-ToCV and TYLCV transgenic tomato plants by RNAiOriginal Papers

F.-M. JIN, J. SONG, J. XUE, H.B. SUN, Y. ZHNAG, S. WANG, Y.-H. WANG

Biologia plantarum 64: 490-496, 2020 | DOI: 10.32615/bp.2020.069

Tomato is an economically important vegetable. Tomato chlorosis virus (ToCV) and Tomato yellow leaf curl virus (TYLCV) are two major viruses that cause serious losses to tomato production. The effective method to control these two viruses is to breed antiviral species by genetic engineering techniques. In order to obtain the RNA interference (RNAi) expression vector of tomato, the coat protein (CP) genes of ToCV and TYLCV were selected in this study. The tandem sequences of the two CP genes were obtained using the recombinant PCR technique. Using Gateway cloning technology, the RNAi expression vector pRNAi-ToCV-TY...

Distribution of Na⁺ in roots and stem bases of buckwheat seedlingsOriginal Papers

W.-Y. ZHAN, Y.-C. YU, L.-X. HOU, C.-Y. LIU, F.-G. ZHAO, Y.-P. ZHANG, H.-B. YANG

Biologia plantarum 64: 485-489, 2020 | DOI: 10.32615/bp.2020.051

The localizations of sodium exclusion are roots and stem base, however, Na⁺ distribution in these localizations is unclear. Here, we used a salt-tolerant buckwheat cultivar Chuanqiao No.1 and a salt-sensitive cultivar TQ-0808 to demonstrate Na⁺ distribution. We found that Na⁺ content was highest in vacuole, the following was in cell wall or free space, and the least was in cytoplasm. Comparative analysis shows that Na⁺ accumulation in vacuole, cell wall, or free space of roots and stem base in 'Chuanqiao No.1' was obviously higher than in 'TQ-0808'; in contrast, Na⁺ accumulation in cytoplasm of...

Changes of cytosine methylation in pecan tissues of different stages by quantitative methylation-sensitive amplified polymorphismOriginal Papers

Z.Z. LIU, F. ZHOU, J. SHANG, F.R. PENG, Z.H. MO, Y.R. LI

Biologia plantarum 64: 473-484, 2020 | DOI: 10.32615/bp.2020.066

Cytosine methylation plays an important role in plant development by regulating gene expressions. However, few studies have investigated methylation changes during the tissue differentiation and development of perennial plants. Here, the fluorescence-labeled methylation-sensitive amplified polymorphism method was used with eight primer combinations to detect methylation in leaves and xylem obtained at the stages of inflorescence emergence (IE), ovary start growth, and fruit maturity (FM) in two pecan (Carya illinoinensis) cvs. Pawnee and Stuart. The results show that the total methylation in the xylem was generally higher than in the leaves...

Transcriptome analysis deciphers the mechanisms of exogenous nitric oxide action on the response of melon leaves to chilling stressSpecial Issue: Gasotransmitters

Q. DIAO, Y. CAO, H. FAN, Y. ZHANG

Biologia plantarum 64: 465-472, 2020 | DOI: 10.32615/bp.2020.021

Chilling stress is a major abiotic factor that limits the growth and productivity of melon (Cucumis melo L.). The application of nitric oxide (NO) can enhance plant tolerance to chilling stress; however, the underlying molecular mechanisms for this process remain poorly understood. In this study, RNA sequencing was performed on melon seedlings exposed to control conditions, chilling stress, or chilling stress in the presence of NO donor sodium nitroprusside (SNP), to identify NO-mediated transcript changes in response to chilling stress. The results identified 488, 1 012, and 1 589 differentially expressed genes (DEGs) between plants in optimum...

The rice Aux/IAA transcription factor gene OsIAA18 enhances salt and osmotic tolerance in ArabidopsisOriginal Papers

G. LI, Y.X. YE, X.Q. REN, M.Y. QI, H.Y. ZHAO, Q. ZHOU, X.H. CHEN, J. WANG, C.Y. YUAN, F.B. WANG

Biologia plantarum 64: 454-464, 2020 | DOI: 10.32615/bp.2019.069

In plants, auxin/indoleacetic acid (Aux/IAA) proteins are transcriptional regulators, which regulate developmental process and responses to phytohormones and stress treatments. A previous study has shown that the rice Aux/IAA transcription factor gene OsIAA18 is induced by salt and osmotic stresses. However, little is known about the regulatory functions of this gene. In this study, the OsIAA18 gene was successfully cloned from rice. Subcellular localization analysis in onion epidermal cells indicated that OsIAA18 was localized to the nucleus. Expression analysis in yeast showed that the full length OsIAA18 exhibited transcriptional activation....

Leaf nutrient homeostasis and maintenance of photosynthesis integrity contribute to adaptation of the pea mutant SGECd^t to cadmiumOriginal Papers

A.A. BELIMOV, I.C. DODD, V.I. SAFRONOVA, K.-J. DIETZ

Biologia plantarum 64: 447-453, 2020 | DOI: 10.32615/bp.2020.061

Cadmium (Cd) is a highly toxic and widespread soil pollutant, which negatively affects various aspects of plant growth and physiology. Here, the role of photosynthesis in response to Cd was investigated in the Cd-tolerant pea (Pisum sativum L.) mutant SGECd^t. The wild type SGE and the mutant SGECd^t were grown in a hydroponic solution supplemented with 1, 3, or 4 µM CdCl₂ for 12 d. Root and shoot biomasses of the Cd-treated SGECd^t were significantly higher than of SGE. Cadmium had little effect on the quantum yield of photosystem II (φPSII) and chlorophyll content of intact leaves of both...

Quantitative trait loci for winter hardiness and other agronomic traits in the progeny of two amphiploid Festulolium hybrids (Festuca pratensis × Lolium perenne) backcrossed twice to tetraploid Lolium perenne Special Issue: Festulolium

K. TAMURA, Y. SANADA, K. TASE, Y. AKIYAMA, A. KUBOTA

Biologia plantarum 64: 439-446, 2020 | DOI: 10.32615/bp.2020.057

To clarify the effects of the introduction of Festuca pratensis-derived genomic regions in a tetraploid Lolium perenne genomic background, we analyzed quantitative trait loci (QTLs) for winter hardiness and eight other agronomic traits using two mapping populations generated by sequential backcrosses of two different amphiploid F. pratensis × L. perenne hybrids to tetraploid L. perenne. We constructed two interspecific linkage maps: FLBC2A (143 DNA markers, 301.2 cM total) and FLBC2C (126 markers, 256.2 cM), based on F. pratensis-derived alleles, with 72 markers in common. Interval mapping detected QTLs for...

Isolation and characterization of the promoter of SEPALLATA1-like gene from Platanus acerifoliaOriginal Papers

S.J. LU, S.S. YI, L. LIU, M.Z. BAO, G.F. LIU

Biologia plantarum 64: 430-438, 2020 | DOI: 10.32615/bp.2020.036

London plane (Platanus acerifolia Wild.) is a famous landscape plant because of its numerous desirable traits except the abundant pollens and seed hairs, which not only pollute the environment but also affect human health. To resolve these problems, we herein isolated and functionally analyzed the promoter of PlacSEP1.1, an orthologous gene of Arabidopsis SEPALLATA1, and investigated the potential usability for cell ablation strategies to engineer reproductive sterility in plants. A 2130 bp 5' upstream region of PlacSEP1.1 was isolated and termed pPlacSEP1.1. Putative motif detections show that there were several...

Effects of exogenous nitric oxide and ethylenediaminetetraacetic acid on cadmium toxicity and accumulation in ryegrassSpecial Issue: Gasotransmitters

Q. ZHANG, Y. Y. ZHU, Y. J. DONG

Biologia plantarum 64: 422-429, 2020 | DOI: 10.32615/bp.2020.046

The effects of exogenous nitric oxide (NO) and ethylenediaminetetraacetic acid (EDTA) on cadmium toxicity and accumulation in ryegrass (Lolium perenne L.) were studied in a hydroponic experiment. The results show that in plants without Cd application, addition of EDTA and sodium nitroprusside (SNP, an exogenous NO donor) significantly reduced the plant height, root length, and root activity of ryegrass, and significantly increased the O₂^*- generation rate and H₂O₂ and malondialdehyde (MDA) content in the aboveground and underground parts of ryegrass. Cadmium stress significantly inhibited ryegrass...

An HD-Zip IV transcription factor protein NbGL3 regulates glandular trichome initiation in tobaccoOriginal Papers

Y.S. TIAN, T.W. DAI, C.X. FAN, J. ZHOU, X.L. REN, Y. XU

Biologia plantarum 64: 378-384, 2020 | DOI: 10.32615/bp.2020.012

Glandular trichomes, a specialized multicellular structure, are considered as biofactories due to their capability to synthesize and secrete a large amount of secondary metabolites. Tobacco leaves have a high density of glandular trichomes that produce huge amounts of secondary metabolites, which can be used as important industrial raw materials. However, molecular mechanism controling glandular trichome development in tobacco still remains largely unknown. In the present study, we found that NbGL3, an HD-Zip IV family gene from Nicotiana benthamiana, was highly expressed in mature leaves, and ethylene or auxin application could increase...

Mannose regulates water balance, leaf senescence, and genes related to stress tolerance in white clover under osmotic stressOriginal Papers

S.Y. ZHAO, W.H. ZENG, Z. LI, Y. PENG

Biologia plantarum 64: 406-416, 2020 | DOI: 10.32615/bp.2020.017

Mannose (MAN), an important monosaccharide, contributes to coping with abiotic stresses in plants. Objectives of this study were to examine whether exogenous MAN (30 mM) could significantly increase drought tolerance and further to reveal MAN-regulated tolerance mechanism in white clover under osmotic stress induced by 18 % (m/v) polyethylene glycol 6000 for 10 d in controlled growth chambers. Results show that the application of MAN significanlty alleviated stress damage and the inhibition of growth and photosynthesis in white clover under osmotic stress. The MAN-induced increase in endogenous MAN content and the accumulation of organic osmolytes...