Diverse functions of GmNLA1 members in controlling phosphorus homeostasis highlight coordinate response of soybean to nitrogen and phosphorus availability

Nitrogen(N) and phosphorus(P) are two essential mineral nutrients for plant growth,which are required in relative high amount in plants.Plants have evolved a series of strategies for coordinately acquiring and utilizing N and P.However,physiological and molecular mechanisms underlying of N and P interactions remain largely unclear in soybean(Glycine max).In this study,interactions of N and P were demonstrated in soybean as reflected by significant increases of phosphate(Pi) concentration in both leaves and roots by N deficiency under Pi sufficient conditions.A total of four nitrogen limitation adaptation(NLA),encoding RING-type E3 ubiquitin ligase were subsequently identified in soybean genome.Among them,transcription of Gm NLA1-1 and Gm NLA1-3 was decreased in soybean by N starvation under Pi sufficient conditions,not for Gm NLA1-2.Suppression of all three Gm NLA1 members was able to increase Pi concentration regardless of the P and N availability in the growth medium,but decrease fresh weight under normal conditions in soybean hairy roots.However,comparted to changes in control lines at two N levels,N deficiency only resulted in a relatively higher increase of Pi concentration in Gm NLA1-1 or Gm NLA1-3 suppression lines,strongly indicating that Gm NLA1-1 and Gm NLA1-3 might regulate P homeostasis in soybean response to N starvation.Taken together,our result suggest that redundant and diverse functions present in Gm NLA1 members for soybean coordinate responses to P and N availability,which mediate P homeostasis.

How Physical Disturbance and Nitrogen Addition Affect the Soil Carbon Decomposition?

The decomposition of soil organic carbon(SOC)plays a critical role in regulating atmospheric CO_(2)concentrations and climate dynamics.However,the mechanisms and factors controlling SOC decomposition are still not fully understood.Here,we conducted a 60 days incubation experiment to test the effects of physical disturbance and nitrogen(N)addition on SOC decomposition.N addition increased the concentration of NO3-by 51%in the soil,but had little effect on the concentration of NH4+.N addition inhibited SOC decomposition,but such an effect differed between disturbed and undisturbed soils.In disturbed and undisturbed soils,application of N decreased SOC decomposition by 37%and 15%,respectively.One possible explanation is that extra N input suppressed microbial N mining and/or increased the stability of soil organic matter by promoting the formation of soil aggregates and incorporating part of the inorganic N into organic matter,and consequently decreased microbial mineralization of soil organic matter.Physical disturbance intensified the inhibition of N on SOC decomposition,likely because physical disturbance allowed the added N to be better exposed to soil microbes and consequently increased the availability of added N.We conclude that physical disturbance and N play important roles in modulating the stability of SOC.

Nitrogen Use Efficiency of Rice Under Cadmium Contamination:Influence of Rice Cultivar Versus Soil Type

There is a need for rice cultivars with high yields and nitrogen(N) use efficiency(NUE), but with low cadmium(Cd) accumulation in Cd-contaminated paddy soils.To determine the relative effects of rice genotype, soil type, and Cd addition on rice grain yield and NUE, a pot experiment consisting of nine rice cultivars was conducted in two types of paddy soils, red soil(RS) and yellow soil(YS),without or with Cd spiked at 0.6 mg kg^(-1).The N supply was from both soil organic N pools and N fertilizers; thus, NUE was defined as the grain yield per unit of total crop-available N in the soil.Cd addition decreased grain yield and NUE in most rice cultivars,which was mainly related to reduced N uptake efficiency(NpUE, defined as the percentage of N taken up by the crop per unit of soil available N).However, Cd addition enhanced N assimilation efficiency(NtUE, defined as the grain yield per unit of N taken up by the crop) by 21.9% on average in all rice cultivars.The NpUE was mainly affected by soil type, whereas NtUE was affected by rice cultivar.Hybrid cultivars had higher NUEs than the japonica and indica cultivars because of their greater biomass and higher tolerance to Cd contamination.Reduction of NUE after Cd addition was stronger in RS than in YS, which was related to the lower absorption capacity for Cd in RS.Canonical correspondence analysis-based variation partitioning showed that cultivar type had the largest effect(34.4%) on NUE, followed by Cd addition(15.2%) and soil type(10.0%).

The relative and combined effects of herbivore assemblage and soil nitrogen on plant diversity

Plant diversity can be affected by both herbivore grazing and soil resources. However, it is unclear if the joint effects of herbivores and soil resources might vary with components of plant diversity. Here, we evaluated the relative and combined effects of herbivore assemblage and soil nitrogen(N) quantity and heterogeneity on the α and β components of plant diversity in a grassland that was subjected to four years of grazing under differing herbivore assemblages(no grazing, cattle grazing, sheep grazing, and mixed grazing). We found that herbivore assemblage combined with soil N quantity explained 41% of the variation in plant α-diversity, while herbivore assemblage combined with soil N heterogeneity explained 15% of the variation in plant β-diversity. The independent effects of herbivore assemblage explained more than those of soil N for both α-and β-diversity(α-diversity: 12% vs. 4%;β-diversity: 18% vs. 16%). We concluded that the effects of herbivores are stronger than those of soil N,and that grazing-induced changes in soil resources are important drivers of plant diversity change, especially α-diversity.Therefore, we suggest that managing herbivore species by accounting for the effects that their grazing can have on soil resources may be significant for plant diversity maintenance.

Nitrogen addition mediates the response of foliar stoichiometry to phosphorus addition: a meta-analysis

Background:Changes in foliar nitrogen(N)and phosphorus(P)stoichiometry play important roles in predicting the efects of global change on ecosystem structure and function.However,there is substantial debate on the efects of P addition on foliar N and P stoichiometry,particularly under diferent levels of N addition.Thus,we conducted a global meta-analysis to investigate how N addition alters the efects of P addition on foliar N and P stoichiometry across different rates and durations of P addition and plant growth types based on more than 1150 observations.Results:We found that P addition without N addition increased foliar N concentrations,whereas P addition with N addition had no efect.The positive efects of P addition on foliar P concentrations were greater without N addition than with N addition.Additionally,the efects of P addition on foliar N,P and N:P ratios varied with the rate and duration of P addition.In particular,short-term or low-dose P addition with and without N addition increased foliar N concentration,and the positive efects of short-term or low-dose P addition on foliar P concentrations were greater without N addition than with N addition.The responses of foliar N and P stoichiometry of evergreen plants to P addition were greater without N addition than with N addition.Moreover,regardless of N addition,soil P availability was more efective than P resorption efciency in predicting the changes in foliar N and P stoichiometry in response to P addition.Conclusions:Our results highlight that increasing N deposition might alter the response of foliar N and P stoichiometry to P addition and demonstrate the important efect of the experimental environment on the results.These results advance our understanding of the response of plant nutrient use efciency to P addition with increasing N deposition.

Plant residues differing in C/N ratio in mulch and soil-the effect of the mulch on nutrient availability and microbial biomass is more pronounced with higher leaching amount

This study investigated the effect of C/N ratio,placement of plant residues,and leaching amounts on soil respiration,microbial biomass,and nutrient availability within four weeks after amendment.Young faba bean shoots(FB,C/N 7)and mature wheat straw(WH,C/N 80)were used as low and high C/N residue,respectively.Soil was unamended,mulched with FB or WH only,or mulched with one residue and mixed with the other residue.Leaching with 5 or 25 mL water was carried out on days 4,12,and 20.Cumulative respiration and microbial biomass N were higher with 25 than 5 mL only in treatments with two residues.WH under FB mulch reduced N availability compared to FB mulch alone,whereas FB under WH increased N availability compared toWHmulch alone.When soils were leached with 25 mL water,available N in FB mulch over WH was lower on day 12,but higher later,compared to WH mulch over FB.In contrast,in WH mulch over FB microbial biomass N increased over time whereas available N decreased.In conclusion,the effect of C/N ratio of the mulch on soil available and microbial biomass N was greater with the higher leaching amount.