Magnesium Fertilizer-Induced Increase of Symbiotic Microorganisms

Publication Date (Web): April 4, 2017 ... These results presumably stemmed from the increase of nutrients supplied by activation-enhanced plant symbio...
0 downloads 0 Views 719KB Size
Subscriber access provided by TRENT UNIV

Article

Magnesium fertilizer-induced increase of symbiotic microorganisms improve forage growth and quality Jihui Chen, Yanpeng Li, Shilin Wen, Andrea Rosanoff, Gaowen Yang, and Xiao Sun J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.6b05764 • Publication Date (Web): 04 Apr 2017 Downloaded from http://pubs.acs.org on April 5, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Journal of Agricultural and Food Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 25

Journal of Agricultural and Food Chemistry

1

Magnesium fertilizer-induced increase of symbiotic

2

microorganisms improve forage growth and quality

3

Jihui Chen1, Yanpeng Li1, Shilin Wen2, Andrea Rosanoff3, Gaowen Yang1, Xiao Sun1*

4 5

1

6

210095, PR China

7

2

8

Hengyang 421001, PR China

9

3

10

College of Agro-Grassland Science, Nanjing Agricultural University, Nanjing

Hengyang Red Soil Experimental Station, Chinese Academy of Agricultural Sciences,

Center for Magnesium Education & Research, 13-1255 Malama St., Pahoa, HI 96778,

USA

11 12 13 14

*

15

Tel & Fax:86-25-84399620.

To whom correspondence should be addressed. E-mail: [email protected],

16

1

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

17

Abstract

18

Magnesium (Mg) plays important roles in photosynthesis and protein-synthesis;

19

however, latent Mg deficiencies are common phenomena that can influence food

20

quality. Nevertheless, the effects of Mg fertilizer additions on plant carbon (C):

21

nitrogen (N): phosphorus (P) stoichiometry, an important index of food quality, are

22

unclear and the underlying mechanisms unexplored. We conducted a greenhouse

23

experiment using low-Mg in–situ soil without and with a gradient of Mg additions to

24

investigate the effect of Mg fertilizer on growth and stoichiometry of maize and

25

soybean, and also measure these plants’ main symbiotic microorganisms: arbuscular

26

mycorrhizal fungi (AMF) and rhizobium, respectively. Our results showed that Mg

27

addition significantly improved both plant species’ growth, and also increased N and

28

P concentrations in soybean and maize, respectively, resulting in low C:N ratio and

29

high N:P ratio in soybean, and low C:P and N:P ratios in maize. These results

30

presumably stemmed from the increase of nutrients supplied by activation-enhanced

31

plant symbiotic microorganisms, an explanation supported by statistically significant

32

positive correlations between plant stoichiometry and plants’ symbiotic

33

microorganisms’ increased growth with Mg addition. We conclude that Mg supply

34

can improve plant growth and alter plant stoichiometry via enhanced activity of plant

35

symbiotic microorganisms. Possible mechanisms underlying this positive plant–soil

36

feedback include an enhanced photosynthetic product flow to roots caused by

37

adequate Mg supply.

38

Key words: magnesium, plant symbiotic microorganisms, plant growth and

39

stoichiometry, maize, soybean

40

2

ACS Paragon Plus Environment

Page 2 of 25

Page 3 of 25

Journal of Agricultural and Food Chemistry

41

Introduction

42

Magnesium (Mg) is essential for the growth and development of plants, and plays an

43

important role in photosynthesis because it is the central element of chlorophyll and is

44

a cofactor of a series of enzymes involved in carbon fixation. Mg also plays a

45

fundamental role in phloem export of photosynthates from source to sink organs such

46

as roots.1 Latent and acute Mg deficiencies in plants are common phenomena because

47

of its unique chemical property–a highly hydrated radius that sorbs less to colloids

48

than other cations.2 Magnesium fertilizer not only increases plant photosynthesis by

49

mitigating Mg deficiencies,3-7 but may also improve other nutrients’ uptake by root

50

via enhancing transport of photosynthetic products to roots. Therefore, the

51

physiological and biochemical changes caused by Mg fertilizer can not only increase

52

plant growth, but may also alter plant stoichiometry which is a key characteristic trait

53

that controls nutrients and energy transfer in food webs.8,9 Understanding the

54

influence of Mg fertilizer on plant stoichiometry should thus provide important new

55

information about physiological and ecological ramifications of mineral nutrients in

56

terrestrial ecosystems. To our knowledge, no study has researched the influences of

57

Mg fertilizer on plant stoichiometry, although such measurements can be very

58

important for predicting plant-to-herbivore energy and nutrient flow.

59

Ecological stoichiometry considers that all organisms are composed of the same

60

major elements [carbon (C), nitrogen (N), and phosphorus (P)]. The balance of these

61

elements as well as their supply affect consumers, and change of plant food

62

stoichiometry measurements can provide perspective to predict the possible effects of

63

fertilizer or other treatments on consumer animal growth.10 Studies of

64

autotroph-herbivore interface (particularly for freshwater ecosystems) show that N or

65

P fertilizer treatment changes plant C:N:P stoichiometry which then influences energy 3

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

66

and mineral flow in these ecosystems.11-13 These studies found that food (plant) with

67

moderate C : P and N : P ratios are most likely to result in efficient element trophic

68

transfer, as excessively low or high C : P and N : P food (plant) ratios are not

69

beneficial to growth of consumers (herbivores).11,13-15 Forage quality studies have

70

generally focused on the contents of crude protein (a reflection of N content), but few

71

studies have shown that Mg fertilizer enhanced protein content in food, and the

72

underlying mechanism is unclear.7

73

Mg fertilizer may enhance N and P acquisition by plant root via improving

74

root growth and perhaps by enhancement of symbiotic microorganisms, which deliver

75

limiting soil minerals (e.g. N and P) to their host plants in return for

76

photosynthetically derived carbon.16-20 There is strong empirical evidence that Mg

77

fertilizer results in dramatic increases in carbohydrate flow to roots,1,3,5 resulting in

78

both enhanced root growth and enlarged contact area of root with soil.1,21-23

79

Additionally, preferential partitioning of photosynthetic carbon to roots to increase

80

limited elements’ uptake has also been reported.21,22 This increase of root

81

carbohydrates caused by Mg fertilizer might also enhance the mutualistic interactions

82

between host plant and microbes such as arbuscular mycorrhizal fungi (AMF) in

83

grasses and rhizobium in legumes. With Mg fertilizer, this increase of both root

84

growth and plant mutualistic microorganisms could together enhance the nutrient and

85

water acquisition by roots, perhaps altering plant growth as well as C:N:P

86

stoichiometry.23

87

In the current study, a greenhouse experiment was conducted to investigate

88

the effects of Mg fertilizer in low Mg soil on forage maize and soybean growth and

89

stoichiometry. The influence of Mg fertilizer on colonization of these plants’

90

mutualistic microorganisms was also evaluated. We hypothesized that: 4

ACS Paragon Plus Environment

Page 4 of 25

Page 5 of 25

Journal of Agricultural and Food Chemistry

91 92 93 94 95

(i) Mg addition in both species would improve plant growth and activate plant mutualistic microorganisms; (ii) Mg addition would enhance N, P and Mg concentrations in leaves (resulting in decreased C:P and C:N ratios) in both species; (iii) Mg addition would bring no change in N:P ratio in maize (a grass) but

96

would increase N:P ratio in soybean (a legume) due to different properties of

97

arbuscular mycorrhizal fungi and rhizobium.

98

Materials and methods

99

Experimental design

100

Acid red-yellow soil in south is usually poor in Mg because of soil acidification and

101

leaching due to high precipitation, and plants in this soil also suffer from P deficiency.

102

Therefore, we collected the acid red-yellow soil from Hengyang Red Soil

103

Experimental Station in Hunan province, and mixed for homogeneity. The five mixed

104

soil samples were air-dried in a shaded and ventilated environment for approximately

105

one month to achieve a constant weight for determination of soil pH and total

106

elements. The soil total N, P, available Mg, and organic carbon concentrations and pH

107

were 0.082%, 0.036%, 0.0015%, 1.33% and 4.3, respectively.

108

A total of 50 plastic pots (20 cm in diameter, 24 cm in depth) were filled with

109

the well-mixed soil, each pot containing 4 kg soil. The soil-filled pots were then

110

divided into two groups of 25 pots per group, resulting in 25 pots for each of the two

111

species (maize or soybean). As done on previous studies conducted at this site, we set

112

5 treatments of Mg addition (0, 20, 50, 100 and 200 mg kg-1 MgCO3) for each group

113

(one species) with 5 replications. The total MgCO3 fertilizer (powder) was calculated

114

according to each treatment concentration and soil weight.

5

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

115

Plant materials

116

Maize and soybean were selected as model species for close relationships with AMF

117

and rhizobium, respectively. At the beginning of May, ~10 maize or soybean seeds

118

were sown in each pot in the greenhouse. We watered the seedlings every other day,

119

and the water level was adjusted using an electronic weigher once every three days to

120

keep similar soil moisture content. The pot position was also changed randomly once

121

every three days to avoid light heterogeneity. After three weeks, the seedlings (~10

122

cm) were thinned in each pot to allow sufficient space for seedling growth with 3

123

similar seedlings kept in each pot. We gently removed the upper soil (~2 cm) from

124

free room in each pot, and then evenly sprinkled corresponding MgCO3 and recovered

125

using “the removed upper soil”. After fertilization, we evenly sprinkled water to help

126

plant uptake.

127

Sampling and chemical analysis

128

After 8 weeks, we harvested the plants. All plants were divided into roots and shoots.

129

The roots were cleaned with tap water and then ultrapure water, and finally blotted

130

dry with superabsorbent paper. One-tenth of fresh roots of maize were used for

131

measuring AMF colonization (see below). The root nodules of soybean were removed,

132

counted, and weighed using ten-thousandth analytical electronic balance after blotting

133

dry with superabsorbent paper. These weights and numbers of soybean nodules were

134

used to quantify the degree of rhizobium colonization. To measure chlorophyll

135

content, about 2 g mature fresh leaves were extracted with 80% (v/v) acetone, and

136

chlorophyll was measured using spectrophotometry.24 Remaining parts of plant

137

samples and nodules were oven-dried at 65℃for 72 h. The nodules, shoots and roots

138

(without rhizobium nodules) were cooled to room temperature in a desiccator and

139

were weighed to determine dry biomass. Leaves and stems were then separated for 6

ACS Paragon Plus Environment

Page 6 of 25

Page 7 of 25

Journal of Agricultural and Food Chemistry

140

each shoot; only mature dried leaves were used for elemental analysis and

141

stoichiometry calculations. In preparation for chemical analyses, all plant samples

142

were ground in 20-inch mesh in Wiley Mill. All samples were kept cool and dry for

143

chemical analysis.

144

AMF colonization: The roots used to measure AMF colonization were cut into

145

approximately 1-cm lengths and were cleared in 10 % (w/v) KOH at 90 °C in a water

146

bath for 30 min, then washed and stained with 0.05 % (w/v) Trypan blue developed

147

by Trouvelet (1986).25 Using a dissection microscope, thirty root segments of each

148

sample were assessed for percentage of root length colonized by AMF.

149

Elemental analyses of leaf samples: Dried mature leaf samples were analyzed for total

150

C and N concentrations (mg g-1) utilizing an elemental analyzer (Vario EL III,

151

Elementar, Germany) and for P and Mg using an inductively coupled plasma emission

152

spectrometer (Iris Advantage 1000, USA) once the samples were digested using

153

trace-metal-grade nitric and perchloric acid, which was diluted in 100 ml of double

154

distilled water.

155

Statistical analysis

156

The data were log-transformed when necessary to meet the parametric test

157

assumptions of normality (Bartlett test) and homogenous variances, and then one-way

158

ANOVA was used to determine the effects of Mg treatment on plant growth, leaf

159

stoichiometry, and colonization rate of AMF and rhizobia. If data after transformation

160

did not meet the parametric test assumptions of normality, the Kruskal-Wallis test was

161

used. Pearson's product-moment correlation was used to analyze the relationships

162

among plant growth, leaf stoichiometry and plant symbiotic microorganisms. Data

163

analyses were performed with R 3.0.2 (R Development Core Team 2005).

7

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

164

Results

165

Effects of magnesium fertilizer on leaf chlorophyll and plant growth

166

Total chlorophyll, chlorophyll a and chlorophyll b concentrations in mature leaves

167

were significantly increased by Mg addition in both species, at >50 mg kg-1 addition

168

level in maize and >20 mg kg-1 Mg addition for soybean (Figure 1). Mg fertilizer

169

showed no significant influence on shoot biomass of maize, but significantly

170

increased the shoot biomass of soybean (Figure 2a). The root biomass of both species

171

increased with low Mg additions (20 or 50 mg kg-1 MgCO3) while high Mg addition

172

(100 – 200 mg kg-1 MgCO3) showed no effects (Figure 2b). Low Mg addition (20 mg

173

kg-1 MgCO3) showed no effects on total biomass, whereas, moderate (50 mg kg-1 or

174

100 mg kg-1 ) Mg additions had significant positive effects on total biomass while

175

high Mg additions had no further positive effect (Figure 2b and c).

176

Effects of magnesium fertilizer on plant mutualistic microorganisms

177

Except for low Mg treatment levels (20 or 50 mg kg-1 MgCO3 ), Mg treatment up to

178

100 mg kg-1 significantly increased AMF colonization in maize, and the effect of

179

further additional Mg (at high Mg treatment 200 mg kg-1) showed no further

180

improved effect (Figure 3a). The rhizobium showed a similar pattern to AMF with Mg

181

addition, reflected in both high nodulation and total nodule weight of each plant in

182

response to Mg addition (Figures 3b and c).

183

Effects of magnesium fertilizer on plant stoichiometry

184

The dry leaf Mg concentration of both species significantly increased with Mg

185

addition (Figure 4), while there was no significant change of C concentration (data not

186

shown in Figure 4). Mg addition showed no significant effects on N concentration in

187

maize leaf, except at the highest level of Mg addition which significantly decreased N

188

concentration. In contrast, all levels of Mg addition >20 mg kg-1 showed a significant 8

ACS Paragon Plus Environment

Page 8 of 25

Page 9 of 25

Journal of Agricultural and Food Chemistry

189

increase of N in soybean leaf. Mg addition, except at the highest level (200 mg kg-1),

190

significantly increased P concentration in maize leaf, whereas there was no significant

191

influence of Mg treatments on P in soybean leaf, except at the highest level of Mg

192

addition, which significantly decreased P concentration (Figure 4).

193

All levels of Mg addition reduced N:P ratio significantly in maize leaf (Figure.

194

4), but Mg addition at levels >20 mg g-1 significantly enhanced N:P ratio in soybean

195

leaf. Furthermore, the N:P ratio in maize leaf was reduced similarly at all levels of Mg

196

addition (20 to 200 mg kg-1 MgCO3) (Figure 4). In contrast, Mg addition of 50 and

197

100 mg kg-1 MgCO3 doubled leaf N:P ratio, and 200 mg kg-1 Mg addition further

198

increased leaf N:P of soybean leaves significantly and substantially another 40%

199

(Figure 4). The C:N ratio in soybean leaves significantly decreased with Mg addition

200

except for 20 mg kg-1 MgCO3, whereas, there were no significant influences on C:N

201

ratio in maize leaves (Figure 4). Mg addition decreased C:P ratio in maize leaves with

202

no difference between treatments, but showed no influence on C:P ratio in soybean

203

leaves except for a significant increase at the highest level of Mg addition (Figure 4).

204

Relationships of plant biomass or stoichiometry with symbiotic microorganisms

205

The average weight and number of individual plant rhizobium nodules showed

206

significant positive correlation with both plant biomass and mature leaf N

207

concentration (resulting in negative relationships between weight of rhizobium and

208

C:N ratio, and positive relationships with N:P ratio) (Table 1). By contrast, the AMF

209

colonization showed no significant relationships with plant biomass and measured

210

elements in mature leaf, but did show a significant negative relationship with N:P

211

ratio (Table 2).

9

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

212

Discussion

213

Influences of magnesium fertilizer on plant growth

214

As in recent studies,6,7 appropriate Mg fertilizer significantly increased chlorophyll

215

content in both maize and soybean, reflecting an increase of photosynthesis under Mg

216

fertilizer conditions. Similar to some previously reported findings that Mg fertilizer

217

increased plant biomass,1,6,7,26 we found that shoot, root and total biomass increased in

218

soybean with Mg addition while in maize only root and total biomass increased. A

219

few studies also have observed no effects of Mg fertilizer on biomass of shoot.6,27-29

220

These inconsistent results may be due to different physiological and biochemical

221

responses of plants and their symbiotic microorganisms to Mg addition.6,29,30 The

222

positive effects of moderate Mg addition on root growth were not seen in either

223

species under high Mg addition conditions. Perhaps this reflects allocation of more

224

photosynthetic C to root mutualistic microorganisms rather than to root growth as a

225

more efficient mode of nutrient acquisition. This interpretation was supported by high

226

AMF colonization in maize and increased ratio of root nodule biomass:root biomass

227

in soybean with Mg addition (Figure S1).

228

Colonization of plant mutualistic microorganisms in response to magnesium

229

fertilizer

230

Rhizobium: As expected, Mg-treated soybean plants had more and larger nodules.

231

Similar results were reported by Kiss et al (2004),27 and they considered that Mg has

232

an important role in the metabolism of the rhizobium bacteria and nodule

233

development, because (N2)-fixing rhizobium strains need ATP that must be present as

234

a Mg-complex.27 Another possible contributing mechanism for the positive influence

235

of Mg addition on rhizobium bacteria may be the increase of carbon flow to root

236

induced by Mg addition,1 making more nutritional C available to rhizobium for 10

ACS Paragon Plus Environment

Page 10 of 25

Page 11 of 25

Journal of Agricultural and Food Chemistry

237

growth. Although we did not find a significant increase of sugar in roots under Mg

238

addition (except for low Mg addition) to support this interpretation, this may be

239

because we only measured the sugar in the roots without nodules. This needs to be

240

tested.

241

AMF: As found here, a previous study showed that Mg addition has a pronounced

242

positive effect on root AMF infection of maize, a result that could not be explained by

243

changes in pH or osmotic pressure of the nutrient solution.28 Conversely, a few other

244

studies reported an inhibitory effect of Mg fertilizer on colonization of mycorrhiza

245

fungi.31,32 These inconsistent results may arise from an imbalance of Mg and other

246

elements, such as Ca, which can disrupt the mycorrhizal association with its host plant,

247

or differences of bacterial strain.31,32 Here, we also suggest that the increase of

248

mutualistic association was attributable to the enhanced phloem export of sucrose

249

under Mg addition conditions (Figure S2).

250

Plant stoichiometry in response to magnesium fertilizer

251

Nitrogen: As our hypothesis predicted, Mg addition doubled N (or protein)

252

concentration in soybean leaf, presumably as a result of the increase of biological

253

nitrogen fixation in larger and more numerous root nodules. In contrast, there was no

254

rise and even a slight decrease in maize leaf N concentration with Mg addition, a

255

possible “dilution effect” due to the increase of biomass. These results suggest that

256

Mg fertilizer may improve protein content in legume-based food as much as nitrogen

257

fertilizer,33 or reduce protein in grass-based food while raising leaf P as might a

258

phosphorus fertilizer34 albeit with different mechanisms. The different responses of

259

the two species can be attributed to the different biochemical roles of their main

260

symbiotic microorganism, i.e. rhizobium and AMF, as it is generally known that

261

rhizobium can fix nitrogen from the atmosphere while AMF mainly delivers various 11

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

262

soil mineral elements, especially P.

263

Phosphorus: These functional differences in microorganisms may also explain

264

differences in the total P content of the two species’ responses to Mg treatments and

265

the marginally significant increase of P in maize leaves with Mg addition not seen in

266

soybean leaves.

267

Magnesium: In previous studies, as in the present study, Mg treatments significantly

268

increased Mg concentration in leaf,6 which can be beneficial to animal nutrition in

269

decreasing35 the risk of grass tetany of herbivores36 and in plant foods destined for

270

human consumption which have shown decreased Mg concentration over time,

271

especially with the high yield cultivars.37

272

C:N:P Ratios: The C:N ratio in leaf of Mg-treated soybean was 50% lower than in

273

non-treated soybean leaf; by contrast, soybean leaf N:P ratio more than doubled with

274

Mg treatment. This is primarily due to the increase of symbiotic N fixation seen in

275

Mg-treated soybean. The decrease of C:P and N:P ratios in maize leaf with Mg

276

addition was associated with an increase of leaf P. According to theories behind

277

stoichiometry studies, decreased C:N (seen in our soybean plants with Mg addition)

278

or C:P (seen in our maize plants with Mg addition) ratios in plants may improve C

279

flow to herbivores.10 Significant correlations between stoichiometry and mutualistic

280

microbes in this study suggest that the differences in leaf C: N : P stoichiometry

281

between maize and soybean come primarily from their differing mutualistic

282

interactions between plant and microbe that are enhanced by Mg fertilizer.

283

Conclusions

284

Our results suggest that moderate Mg fertilization improved plant growth and altered

285

C:N:P stoichiometry primarily via enhancement of mutualistic interactions between

286

host plant and microbes as well as by promoting root growth. The potential 12

ACS Paragon Plus Environment

Page 12 of 25

Page 13 of 25

Journal of Agricultural and Food Chemistry

287

mechanisms underlying this positive effect of Mg addition include an enhanced

288

photosynthetic production flow from source leaves that promotes root growth and

289

“feeds” mutualistic microbes, and, possibly, a direct, positive Mg effect on AMF and

290

rhizobium development that delivers more nutrients to the host plants. Such change of

291

stoichiometry brought about by Mg addition may favor nutrient and energy transfer in

292

food webs. Our study has important implications for understanding the influence of

293

Mg fertilizer and its underlying mechanisms on plant quality, and contributes

294

information for farmland management strategies that could improve food quality and

295

yield.

296

Acknowledgments

297

We thank Shuijing Hu for helpful suggestion on the experiment, and Christina West

298

for proofreading the manuscript. This work was financially supported by National

299

Natural Science Foundation of China (NSFC 600030), Basic research program of

300

Jiangsu province (Natural Science Foundation) -Youth Foundation (BK20150665),

301

and Student Research Training Program (1526A01).

302

Supporting Information Available: [Methods of soluble carbohydrate analyses;

303

Results of rhizobium nodule to root biomass ratio in soybean with Mg addition (Fig.

304

S1); Soluble carbohydrate in leaf and roots of maize and soybean under Mg addition

305

(Fig. S2).] This material is available free of charge via the Internet at

306

http://pubs.acs.org.

307

13

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

308

References

309

1.

310

alleviating photooxidative damage. Physiol. Plant. 2008, 133, 692–704.

311

2.

312

urgent realistic problem. Crop J. 2015, DOI: 10.1016/j.cj.2015.1011.1003.

313

3.

314

magnesium nutritional imbalance in plants. Plant Soil 2013, 368, 87–99.

315

4.

316

D.; de Silveira, H. R. O. Physiological and biochemical impacts of

317

magnesium-deficiency in two cultivars of coffee. Plant Soil 2014, 382, 133–150.

318

5.

319

Magnesium deficiency in sugar beets alters sugar partitioning and phloem loading in

320

young mature leaves. Planta 2005, 220, 541–549.

321

6.

322

nutrient status, and growth of maize (Zea mays L.) upon MgSO4 leaf-application.

323

Front. Plant Sci. 2015, 5, 781.

324

7.

325

and yield in Mg-deficient faba beans (Vicia faba) by MgSO4 foliar fertilization. J.

326

Plant Nutr. Soil Sci. 2014, 177, 741–747.

327

8.

328

Tiedemann, M.; Hodapp, D. Unifying ecological stoichiometry and metabolic theory

329

to predict production and trophic transfer in a marine planktonic food web. Philos.

Cakmak, I.; Kirkby, E. A. Role of magnesium in carbon partitioning and

Guo, W.; Nazim, H.; Liang, Z.; Yang, D. Magnesium deficiency in plants: an

Verbruggen, N.; Hermans, C. Physiological and molecular responses to

Da Silva, D. M.; Brandão, I. R.; Alves, J. D.; de Santos, M. O.; de Souza, K. R.

Hermans, C.; Bourgis, F.; Faucher, M.; Strasser, R. J.; Delrot, S.; Verbruggen, N.

Jezek, M.; Geilfus, C.-M.; Bayer, A.; Mühling, K.-H. Photosynthetic capacity,

Neuhaus, C.; Geilfus, C.-M.; Muehling, K.-H. Increasing root and leaf growth

Moorthi, S. D.; Schmitt, J. A.; Ryabov, A.; Tsakalakis, I.; Blasius, B.; Prelle, L.;

14

ACS Paragon Plus Environment

Page 14 of 25

Page 15 of 25

Journal of Agricultural and Food Chemistry

330

Trans. R. Soc. B 2016, 371, 20150270.

331

9.

332

homeostasis among autotrophs and heterotrophs. Oikos 2010, 119, 741–751.

333

10. Sterner, R. W.; Elser, J. J., Growth efficiency. In Ecological Stoichiometry: The

334

Biology of Elements From Molecules to the Biosphere; Princeton University Press:

335

Princeton, NJ, 2002; pp 225–226.

336

11. Elser, J. J. Nutritional constraints in terrestrial and freshwater food webs. Nature

337

2000, 408, 578–580.

338

12. Dickman, E. M.; Newell, J. M.; González, M. J.; Vanni, M. J. Light, nutrients,

339

and food-chain length constrain planktonic energy transfer efficiency across multiple

340

trophic levels. Proc. Natl. Acad. Sci. U.S.A. 2008, 105, 18408–18412.

341

13. Meunier, C. L.; Gundale, M. J.; Sánchez, I. S.; Liess, A. Impact of nitrogen

342

deposition on forest and lake food webs in nitrogen-limited environments. Global

343

Change Biol. 2016, 22, 164–179.

344

14. Cease, A. J.; Fay, M.; Elser, J. J.; Harrison, J. F. Dietary phosphate affects food

345

selection, post-ingestive P fate, and performance of a polyphagous herbivore. J. Exp.

346

Biol. 2015, 219, 64–72.

347

15. Boersma, M.; Elser, J. J. Too much of a good thing: on stoichiometrically

348

balanced diets and maximal growth. Ecology 2006, 87, 1325–1330.

349

16. Fellbaum, C. R.; Gachomo, E. W.; Beesetty, Y.; Choudhari, S.; Strahan, G. D.;

350

Pfeffer, P. E.; Kiers, E. T.; Bücking, H. Carbon availability triggers fungal nitrogen

351

uptake and transport in arbuscular mycorrhizal symbiosis. Proc. Natl. Acad. Sci.

Persson, J.; Kato, S. To be or not to be what you eat: regulation of stoichiometric

15

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

352

U.S.A. 2012, 109, 2666–2671.

353

17. Johnson, N. C. Resource stoichiometry elucidates the structure and function of

354

arbuscular mycorrhizas across scales. New Phytol. 2010, 185, 631–647.

355

18. Kiers, E. T.; Duhamel, M.; Beesetty, Y.; Mensah, J. A.; Franken, O.; Verbruggen,

356

E.; Fellbaum, C. R.; Kowalchuk, G. A.; Hart, M. M.; Bago, A. Reciprocal rewards

357

stabilize cooperation in the mycorrhizal symbiosis. Science 2011, 333, 880–882.

358

19. Revillini, D.; Gehring, C. A.; Johnson, N. C. The role of locally adapted

359

mycorrhizas and rhizobacteria in plant-soil feedback systems. Funct. Ecol. 2016, 30,

360

1086–1098.

361

20. Fellbaum, C. R.; Mensah, J. A.; Cloos, A. J.; Strahan, G. E.; Pfeffer, P. E.; Kiers,

362

E. T.; Bücking, H. Fungal nutrient allocation in common mycorrhizal networks is

363

regulated by the carbon source strength of individual host plants. New Phytol. 2014,

364

203, 646–656.

365

21. Cakmak, I.; Hengeler, C.; Marschner, H. Partitioning of shoot and root dry matter

366

and carbohydrates in bean plants suffering from phosphorus, potassium and

367

magnesium deficiency. J. Exp. Bot. 1994, 45, 1245–1250.

368

22. Lemoine, R.; La Camera, S.; Atanassova, R.; Dédaldéchamp, F.; Allario, T.;

369

Pourtau, N.; Bonnemain, J.-L.; Laloi, M.; Coutos-Thévenot, P.; Maurousset, L.

370

Source-to-sink transport of sugar and regulation by environmental factors. Front.

371

Plant Sci. 2013, 4, 2.

372

23. Farhat, N.; Elkhouni, A.; Zorrig, W.; Smaoui, A.; Abdelly, C.; Rabhi, M. Effects

373

of magnesium deficiency on photosynthesis and carbohydrate partitioning. Acta 16

ACS Paragon Plus Environment

Page 16 of 25

Page 17 of 25

Journal of Agricultural and Food Chemistry

374

Physiol. Plant. 2016, 38, 1–10.

375

24. Porra, R.; Thompson, W.; Kriedemann, P. Determination of accurate extinction

376

coefficients and simultaneous equations for assaying chlorophylls a and b extracted

377

with four different solvents: verification of the concentration of chlorophyll standards

378

by atomic absorption spectroscopy. Biochim. Biophys. Acta Bioenerg. 1989, 975, 384–

379

394.

380

25. Trouvelot, A. Mesure du taux de mycorhization VA d'un systeme radiculaire.

381

Recherche de methodes d'estimation ayant une significantion fonctionnelle.

382

Mycorrhizae Physiol. Gen. 1986, 217–221.

383

26. Farhat, N.; Rabhi, M.; Krol, M.; Barhoumi, Z.; Ivanov, A. G.; McCarthy, A.;

384

Abdelly, C.; Smaoui, A.; Huener, N. P. A. Starch and sugar accumulation in Sulla

385

carnosa leaves upon Mg2+ starvation. Acta Physiol. Plant. 2014, 36, 2157–2165.

386

27. Kiss, S. A.; Stefanovits-Bányai, E.; Takács-Hájos, M. Magnesium-content of

387

rhizobium nodules in different plants: the importance of magnesium in

388

nitrogen-fixation of nodules. J Am. Coll. Nutr. 2004, 23, 751S–753S.

389

28. Gryndler, M.; Vejsadová, H.; Vančura, V. The effect of magnesium ions on the

390

vesicular—arbuscular mycorrhizal infection of maize roots. New Phytol. 1992, 122,

391

455–460.

392

29. Farhat, N.; Ivanov, A. G.; Krol, M.; Rabhi, M.; Smaoui, A.; Abdelly, C.; Hüner, N.

393

P. Preferential damaging effects of limited magnesium bioavailability on photosystem

394

I in Sulla carnosa plants. Planta 2015, 241, 1189–1206.

395

30. Laing, W.; Greer, D.; Sun, O.; Beets, P.; Lowe, A.; Payn, T. Physiological impacts 17

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

396

of Mg deficiency in Pinus radiata: growth and photosynthesis. New Phytol. 2000, 146,

397

47–57.

398

31. Jarstfer, A.; Farmer-Koppenol, P.; Sylvia, D. Tissue magnesium and calcium

399

affect arbuscular mycorrhiza development and fungal reproduction. Mycorrhiza 1998,

400

7, 237–242.

401

32. Anderson, R.; Liberta, A.; Dickman, L. Interaction of vascular plants and

402

vesicular-arbuscular mycorrhizal fungi across a soil moisture-nutrient gradient.

403

Oecologia 1984, 64, 111–117.

404

33. Thanapornpoonpong, S. N.; Vearasilp, S.; Pawelzik, E.; Gorinstein, S. Influence

405

of various nitrogen applications on protein and amino acid profiles of amaranth and

406

quinoa. J. Agric. Food Chem. 2008, 56, 11464–11470.

407

34. Zhang, W.; Liu, D.; Liu, Y.; Chen, X.; Zou, C. Overuse of phosphorus fertilizer

408

reduces the grain and flour protein contents and zinc bioavailability of winter wheat

409

(Triticum aestivum L.). J. Agric. Food Chem. 2017, 65(8), 1473–1482.

410

35. Cakmak, I. Magnesium in crop production, food quality and human health. Crop

411

Pasture Sci. 2015, 66, I–II.

412

36. Aydin, I.; Uzun, F. Potential decrease of grass tetany risk in rangelands

413

combining N and K fertilization with MgO treatments. Eur. J. Agron. 2008, 29, 33–

414

37.

415

37. Rosanoff, A. Changing crop magnesium concentrations: impact on human health.

416

Plant Soil 2013, 368, 139–153.

417 418 18

ACS Paragon Plus Environment

Page 18 of 25

Page 19 of 25

Journal of Agricultural and Food Chemistry

419

Figure Captions

420

Figure 1 The effect of magnesium addition (20, 50, 100, and 200mg kg-1 MgCO3) to

421

acid red-yellow (low Mg) soil on total chlorophyll (a), chlorophyll a (b) and

422

chlorophyll b (c) in maize and soybean leaves. Different letter (capital for maize and

423

lowercase for soybean) indicate significant differences between treatment means

424

(Student-Newman-Keuls test, p< 0.05).

425

Figure 2 The influence of magnesium additions (20, 50, 100, and 200mg kg-1 MgCO3)

426

to acid red-yellow (low Mg) soil on shoot (a) and root biomass (b), and shoot:root

427

biomass ratio (c) in maize and soybean. Different letter (capital for maize and

428

lowercase for soybean) indicate significant differences between treatment means

429

(Student-Newman-Keuls test, p< 0.05).

430

Figure 3 The effect of magnesium additions (20, 50, 100, and 200mg kg-1 MgCO3) to

431

acid red-yellow soil on

432

rhizobium in soybean. Different letter indicate significant differences between

433

treatment means (Student-Newman-Keuls test, p< 0.05).

434

Figure 4 Nitrogen (N), phosphorus (P), magnesium (Mg) concentrations and carbon

435

(C):N:P ratios in leaves of maize and soybean under different magnesium additions

436

(20, 50, 100, and 200mg kg-1 MgCO3) to acid-red-yellow soil. Different letter (capital

437

for maize and lowercase for soybean) indicate significant differences between

438

treatment means (Student-Newman-Keuls test, p< 0.05).

infection rate of AMF (a) in maize roots and (b, c)

19

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

Page 20 of 25

439

Table 1 Results of Soybean relationships (Pearson’s product-moment correlation)

440

among shoot biomass (SB), leaf stoichiometry, and its symbiotic microorganisms.

441

The*, and ** represent significance at α = 0.05, and 0.01, respectively, and * indicate

442

marginal significance (0.06>α > 0.05). Characteristic TNR Chl TWR 0.89* 0.91* TNR 0.82 Chl SB N P C:N C:P

SB 0.88* 0.98** 0.87*

N 0.98** 0.94* 0.86* 0.90

P -0.0008 -0.39 -0.13 -0.41 -0.18

C:N -0.98** -0.9* -0.86 -0.86 -0.995** 0.11

C:P 0.31 0.66 0.38 0.65 0.48 -0.95* -0.42

N:P 0.91* 0.97** 0.83 0.93* 0.98** -0.38 -0.96** 0.65

443

Note TWR= average total weight of nodules/plant, TNR = average total number of rhizobium

444

nodules/plant, ChI, Chlorophyll, N nitrogen, P phosphorus, C carbon.

445

20

ACS Paragon Plus Environment

Page 21 of 25

Journal of Agricultural and Food Chemistry

446

Table 2 Results of Maize relationships (Pearson’s product-moment correlation)

447

among shoot biomass (SB), leaf stoichiometry, and its symbiotic microorganisms. The

448

* and ** represent significance at α = 0.05, 0.01, respectively. Characteristic Chl AMF 0.99** Chl SB N P C:N C:P

SB 0.83 0.89*

N -0.71 -0.69 -0.80

P 0.56 0.61 0.31 0.12

C:N 0.61 0.60 0.76 -0.99** -0.22

C:P -0.71 -0.74 -0.46 0.11 -0.97** -0.01

N:P -0.94* -0.96* -0.80 0.62 -0.71 -0.53 0.85

449

Note AMF arbuscular mycorrhizal fungi, N nitrogen, P phosphorus, C carbon, and bold letters

450

indicate significant relationships (p