Root exudates are an important pathway for plant–microbial interactions and are highly sensitive to climate change. However, how extreme drought affects root exudates and the main components, as well ...as species‐specific differences in response magnitude and direction, are poorly understood. In this study, root exudation rates of total carbon (C) and its components (e.g., sugar, organic acid, and amino acid) were measured under the control and extreme drought treatments (i.e., 70% throughfall reduction) by in situ collection of four tree species with different growth rates in a subtropical forest. We also quantified soil properties, root morphological traits, and mycorrhizal infection rates to examine the driving factors underlying variations in root exudation. Our results showed that extreme drought significantly decreased root exudation rates of total C, sugar, and amino acid by 17.8%, 30.8%, and 35.0%, respectively, but increased root exudation rate of organic acid by 38.6%, which were largely associated with drought‐induced changes in tree growth rates, root morphological traits, and mycorrhizal infection rates. Specifically, trees with relatively high growth rates were more responsive to drought for root exudation rates compared with those with relatively low growth rates, which were closely related to root morphological traits and mycorrhizal infection rates. These findings highlight the importance of plant growth strategy in mediating drought‐induced changes in root exudation rates. The coordinations among root exudation rates, root morphological traits, and mycorrhizal symbioses in response to drought could be incorporated into land surface models to improve the prediction of climate change impacts on rhizosphere C dynamics in forest ecosystems.
Extreme drought significantly decreased root exudation rates of total C and sugar, and amino acid but increased root exudation rate of organic acid. Trees with relatively high growth rates were more responsive to drought in terms of root exudation rates compared with trees with relatively low growth rates.
The present study was conducted during wheat growing season (from November to June 2017 ) at Grdmalla village, Qushtapa district, Erbil governorate with Global Positioning System (GPS) reading of 360 ...01 N , 440 01 E and 413.8m above sea level to study the impact of crop rotation or cultivation of wheat after some vegetable crops and wheat itself such as broccoli, tomato, pepper, cucumber, eggplant and wheat. The results showed that the lowest infection percentage was observed in case of cultivation of wheat after wheat which was 30% in case of cultivation of wheat after wheat, while this value raised to 70-90% in case of cultivation of wheat after the mentioned vegetables. The increase in infection percentage of plant roots with mycorrhizal fungi caused significant increase in wheat yield, phosphorus and protein content. The wheat yield increased from 2.50 Mega gram ha-1 to 4.86 Mega gram ha-1(ton ha-1) in case of cultivation wheat after wheat and broccoli respectively. On the other hand, the protein percentage was increased from 12.20 to 16.50% in case of cultivation of wheat after wheat and cultivation of wheat after broccoli respectively. The significant correlation was recorded between both of yield and protein content of wheat with mycorrhizal infection with correlation coefficient values of (r=0.89 ** and 0.99**) respectively.
Introduction. The effective use of mycorrhizal inoculants poses a challenge for Cuban agriculture. Sweet potato is an important crop for human and animal nutrition, being a mycorrhizal crop with a ...successful breeding program. Objective. To determine whether all sweet potato cultivars respond to inoculation and if the effectiveness of inoculants varies among cultivars and planting seasons. Materials and methods. Two experiments were conducted during 2010 - 2012 in Eutric Cambisols in Villa Clara, Cuba, one for each planting season and repeated twice. Seventeen cultivars were evaluated for their response to the application of three inoculants, in the presence of a half the fertilization dose, and three non-inoculated treatments with fertilization levels of 0, 50, and 100 % of the nitrogen, phosphorus, and potassium dose (100 % NPK). A split plot design was used. Root yields, colonization frequency, and mycorrizal spore production were evaluated as response variables. Results. Cultivars responded positively to inoculation and fertilization, showing differences in yields. However, the highest yields were obtained when inoculated with Rhizoglomus irregulare/ INCAM-11, surpassing (p≤0.05) those obtained with only 50 % of the NPK dose. In the rainy season with higher yields, the differentiation between inoculants was more pronounced, and in thirteen and nine of the cultivars, yields obtained with INCAM-11 were higher (p≤0.05) to those obtained with Glomus cubense/ INCAM-4 and 100 % NPK, respectively. In the dry season, no significant differences were found between yields obtained by inoculating INCAM-11 or INCAM-4 or applying 100 % NPK. In both seasons, inoculation with Funneliformis mosseae/ INCAM-2 was consistently lower. Colonization frequencies and spore production were always higher (p≤0.05) when INCAM-11 was inoculated. Conclusion. Under these soil conditions evaluated, inoculation with INCAM-11 showed higher effectiviveness for all cultivars and planting seasons, resulting in a higher yields and mycorrhizal performance indicators.
The patterns and mechanisms underlying the effects of different types of biochar on crop dry matter accumulation and uptake of major soil minerals are uncertain. This study demonstrated the positive ...effects of adding pyrochar (PC) and hydrochar (HC) to calcareous soils on nutrient uptake by maize seedlings and revealed the important role of mycorrhizal colonization. The effects depended on the type of biochar added and the type of nutrient evaluated. The dry weights of maize seedlings were higher in the HC and PC groups than in the control group, and the P accumulation was 17% higher than that of the control. Adding PC significantly increased Zn accumulation and the concentration and accumulation of Cu in maize seedlings, whereas adding HC increased the Fe concentration. Applying PC and HC also promoted mycorrhizal colonization of maize roots, and P, Zn, and Cu accumulations in the plant were positively correlated with the mycorrhizal colonization rate. This study found that applying PC and HC to calcareous soil at the tested application rate promotes the uptake of some mineral nutrients by maize at the seedling stage, and this effect was at least partially influenced by an increased mycorrhizal colonization rate in the plant root system.
Arbuscular mycorrhizal (AM) fungi protect plants against aluminum (Al) toxicity, but the mechanisms of Al and phosphorus (P) interactions in relation to Al tolerance in mycorrhizal plants are only ...poorly understood. In this study, varying Al and P treatments were applied to soybean plants cultivated in the presence or absence of three different AM fungi. The results showed that plants in symbiotic association with Gigaspora margarita displayed higher Al tolerance than Rhizophagus irregularis or Glomus claroideum. The effectiveness of G. margarita appeared to be associated with more abundant arbuscules and less affected intraradical hyphae compared to no Al controls. The highest levels of Al toxicity mitigation were observed with the combination of high P availability and AM fungal inoculation, which was associated with a concomitant increase in the expression of the AM-inducible phosphate (Pi) transporter gene GmPT9 in soybean. Taken together, these results suggest that AM symbiosis can alleviate Al toxicity in soybean through enhanced P nutrition, as well as, the alteration of the abundance of mycorrhizal infection structures. These findings highlight the importance of P nutrition status in ameliorating Al toxicity in mycorrhizal plants.
Optimization of phosphorus (P) fertilization is important for balancing soil fertility especially in vertisol to support economic crop production. The objective of the study was to determine the ...impact of P fertilization (1998 to 2014) on crop yield and nutrient uptake, and soil fertility under continuous annually tilled corn (Zea mays L.)-wheat (Triticum aestivum L.) system in semi-arid Mediterranean conditions. The study was conducted on Arik clay (isohyperthermic, fine clay Typic Haploxerert) using randomized complete block design with four replications for each treatment at the research farm of the Dept. of Soil Science and Plant Nutrition, Çukurova University, Adana, Turkey. P fertilizer at 0, 50, 100, 200 kg P
2
O
5
ha
−1
as triple superphosphate (TSP), respectively was applied a week before planting corn. Results showed that increasing P fertilization rates significantly decreased the number of mycorrhizal spores associated with corn roots. Similarly, a 10% decrease in corn root mycorrhizal colonization was observed with 200 kg P
2
O
5
ha
−1
fertilization. In the control treatment, corn yield was 4.3 Mg ha
−1
as compared to 5.6, 5.7 and 6.1 Mg ha
−1
in 50, 100 and 200 kg of P
2
O
5
/ha, respectively. The relationship between P fertilization and relative yield showed that more than 95% of the corn yield was produced when P applied at 100 kg P
2
O
5
ha
−1
. While P fertilization significantly increased the leaf N, P, and K contents but decreased the leaf Zn, Fe and Mn contents, as compared with the control. However, P fertilization did not consistently affect the grain N and P contents. Both physiological efficiency- and agronomic efficiency of P fertilization have shown a significant non-linear increase than that of the control. Total organic C (TOC) and total N (TN) concentrations were more than 34 and 26% higher in 100 and 200 kg P
2
O
5
ha
−1
rates as compared with the control. Likewise, available P (AP), manganese (Mn) and zinc (Zn) concentrations increased with an increase in P fertilization rates. The AP, Mn and Zn contents significantly stratified by P fertilization. Our results suggested that 100 kg P
2
O
5
ha
−1
is optimum to sustain Vertisol fertility for supporting economic corn production in the Mediterranean climates of Turkey.
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