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Japanese larch (Larix kaempferi = L. leptolepis) is often characterized by its high growth rate with heterophyllous shoots, but the functional differences of heterophyllous shoots still remain unclear. Recently, abrupt high temperature and drought during spring induced high photosynthetic rate via change in leaf morphology of the deciduous habit. In order to reveal the photosynthetic characteristics of both short and long-shoot needles of sunny canopy of the larch trees using a canopy tower, we calculated the seasonal change of gas exchange characters and leaf mass per area (LMA) and foliar nitrogen content (N) of heterophyllous needles: short and long-shoot needles over 3 years. No marked difference in light-saturated photosynthetic rates (Psat) was observed between short and long shoots after leaf maturation to yellowing, although the difference was obvious in a specific year, which only shows that seasonal change in temperature and soil moisture determines the in situ photosynthetic capacity of needles. The large annual and seasonal variations in Psat in both shoots were found to be mainly determined by climatic variations, while shoot types determined the strategy of their photosynthetic N utilization as well as the stomatal regulation.

This review discusses observed impacts from different climate change-driven pressures on mangrove's role in modulating trace metal transfer at the land-ocean interface. It contributes to the literature in a global context and shows mangroves as mitigators or providing positive feedback to metal mobilization. Most chalcophile metals 2+ accumulate in mangrove soils associated with sulfides while high sedimentation rates avoid their oxidation. Exudation of oxygen by roots fixates Fe, which co-precipitates metals as oxyhydroxides in the rhizosphere. These two biogeochemical processes reduce trace metal availability to plants and their mobility within estuaries. However, climate change-driven pressures alter this geochemical equilibrium. Increasing atmospheric CO 2 and temperature, and the intensity and frequency of extreme climatic events, have proved to affect mangrove functioning and cover, but no direct observation on the impact on metal biogeochemistry is presently available, whereas sea level rise and saline intrusion impacts on the fate of metals have already been observed. Sea level rise increases erosion, that dissociates deposited sulfides releasing metals to the water column. Released metals adsorb onto suspended particles and can re-deposit in the estuary or are exported to continental shelf sediments. Saline intrusion may oxidize deeper sediment layers releasing metals to porewaters. Part of the mobilized metals may remain in solution complexed with DOM and have their bioavailability increased, as shown by high bioaccumulation factors and biomagnification and high metal concentrations in the estuarine biota, which results in higher human exposure through fisheries consumption. Since erosion occurs preferentially at the sea border and higher sedimentation at the higher reaches of the estuary, triggering mangroves migration landward, spatial gradients are formed, and shall be taken into consideration when planning mitigation or adaptation strategies. These observations suggest disruption of traditional humans dwelling in mangrove dominated coastlines by increasing contamination of coastal fisheries, often the principal protein source for those groups and an important source of income. Further research into the environmental and socioeconomic impacts of climate change driven alterations to metal biogeochemical processes in mangroves as contaminant levels are expected to increase.

Aims Understanding mechanisms underlying N use efficiency (NUE) after luxury consumption and nitrate deprivation is crucial to crop productivity. The aim was to elucidate the importance of photosynthesis, assimilatory nitrate reduction and N-reserve remobilization to NUE in cotton. Methods Plants were exposed to three conditions in nutrient solution: (a) previous exposure to high nitrate supply (10 mM) for long-term (8 days); (b) nitrate deprivation (NO 3 − withdrawal) for 8 days followed by (c) an early N-deficiency for 4 days. Results Plants supplied with nitrate excess were able to display increment in shoot NUE related to dry matter gain, whereas photosynthetic N use efficiency did not change, evidencing that excess N per se was not able to improve CO 2 assimilation. Nitrate reductase (NR) activity was crucial to remobilize stored nitrate through deprivation phase and free amino acids, total proteins, and chlorophylls were also essential to N-remobilization. High NUE was important to kept high root growth rates throughout deprivation and early deficiency phases. Despite the great decrease in chlorophyll content, PSII and PSI activities were kept stable until the onset of early N-deficiency, when cotton plants displayed high shoot NUE. Conclusions These responses are closely associated with high NR activity and sustaining of photosynthesis, which contribute to N-homeostasis in different nutritional regimes.

Nitrogen (N) fertilization and fungicides are important tools in order to achieve high yields and quality in wheat (Triticum aestivum L.), although its use may affect the expression of foliar diseases such as leaf rust (LR) (Puccinia triticina Eriks.). An approach focused on the impact of LR and its interaction with fungicides mixtures and N fertilization rates could be useful to improve the modelling of crop N dynamics and enhance grain yield and quality in the context of the integrated management. Our study was designed to determine the additive effects of carboxamide fungicides (TSC) to a double triazole-strobilurin (TS) mixture under three N fertilization rates on the LR disease progress, healthy area duration (HAD), grain yield and N dynamics during two years. Main plots corresponded to three fungicide treatments and three N doses were the sub-plots. LR disease progress, HAD, yield, N remobilization (NREM), N post-anthesis absorption (NPA), N stored in grains (NG) and %N in grains (%Ng) were evaluated. LR severity increased at higher N rates. TSC applications produced the major decreases on LR severity and the main increases in HAD, which resulted in the higher yield increases (+2726 kg/ha). The %Ng increased with the application of fungicides when LR was controlled. LR infections generated reductions in NREM, NPA and NG, a response that could be explained by decreases in aboveground biomass and yield, coupled with reductions on N harvest index and N remobilization efficiency. Combined effect of TSC fungicides and increases in N dose showed the largest increases in NREM, NPA and NG.

Zinc (Zn) deficiency is a global nutritional problem that is reduced through agronomic biofortification. In the current study, the effects of foliar spraying of exogenous ZnSO4·7H2O (0.2% in Quzhou and 0.3% in Licheng, w/v) and/or sucrose (10.0%, w/v) on maize (Zea mays L.) agronomic traits; concentrations of Zn, iron (Fe), calcium (Ca), total phosphorus (P), phytic acid (PA) P, carbon (C), and nitrogen (N); C/N ratios; and Zn and Fe bioavailability (as evaluated by molar ratios of PA/Zn, PA × Ca/Zn, PA/Fe and PA × Ca/Fe) in maize grains were studied under field conditions for two years at two experimental locations. The results confirmed that there were no significant differences in maize agronomic traits following the various foliar treatments. Compared with the control treatment of foliar spraying with deionized water, foliar applications of Zn alone or combined with sucrose significantly increased maize grain Zn concentrations by 29.2–58.3% in Quzhou (from 18.4–19.9 to 25.2–29.6 mg/kg) and by 39.8–47.8% in Licheng (from 24.9 to 34.8–36.8 mg/kg), as well as its bioavailability. No significant differences were found between the foliar spraying of deionized water and sucrose, and between Zn-only and “sucrose + Zn” at each N application rate and across different N application rates and experimental sites. Similar results were observed for maize grain Fe concentrations and bioavailability, but the Fe concentration increased to a smaller extent than Zn. Foliar Zn spraying alone or with sucrose increased maize grain Fe concentrations by 4.7–28.4% in Quzhou (from 13.4–17.1 to 15.2–18.5 mg/kg) and by 15.4–25.0% in Licheng (from 24.0 to 27.7–30.0 mg/kg). Iron concentrations were significantly and positively correlated with Zn at each N application rate and across different N application rates and experimental locations, indicating that foliar Zn spraying facilitated the transport of endogenous Fe to maize grains. Therefore, foliar Zn spraying increased the Zn concentration and bioavailability in maize grains irrespective of foliar sucrose supply while also improving Fe concentrations and bioavailability to some extent. This is a promising agricultural practice for simultaneous Zn and Fe biofortification in maize grains, i.e., “killing two birds with one stone”.

Excessive application of fertilizers in drip-irrigated wheat production can suppress yields, lower nutrient utilization efficiency, and lead to economic and environmental issues such as nitrogen residues in the soil. Based on a recommended fertilizer application (RF) strategy that takes into account target yield and nutrient requirements, this study explores the responses of wheat plant traits, changes in topsoil and subsoil nutrients, fertilizer utilization, and economic benefits under this strategy. From 2022 to 2023, a field experiment was conducted in a typical oasis spring wheat production area at the northern foot of the Tianshan Mountains in Xinjiang. The treatments included no fertilizer control (CK), the farmer’s conventional practice (FP), recommended fertilizer (RF), RF with nitrogen omission (RF-N), phosphorus omission (RF-P), and potassium omission (RF-K). The results showed that compared with FP, the RF reduced 91 kg N ha−1 (30.3%) and 33 kg P2O5 ha−1 (24.8%) in 2022, and 69 kg N ha−1 (23.0%) and 2 kg P2O5 ha−1 (1.5%) in 2023. The effect in 2023 was better; RF also decreased the NO3−1-N residue in the 0–100 cm soil layer by 40.1 kg N ha−1 compared with FP, with no significant difference in wheat grain yield (RF: 5382.9 kg ha−1) or economic benefit (RF: USD 1613.1 ha−1). Furthermore, there were no significant differences between RF and FP in pre-anthesis NP transport or post-anthesis NP accumulation; however, RF significantly increased pre-anthesis potassium transport volume (15.8%) and transport rate (12.5%). RF led to a 16.3% increase in nitrogen utilization efficiency (NUE), while there was no significant difference in phosphorus utilization efficiency (PUE) compared with FP. The fertilizer yield effect for RF was evaluated as N > P > K. Correlation analysis indicated that grain yield was significantly positively correlated with pre-anthesis NPK transport and post-anthesis NP accumulation. It was also positively correlated with organic matter, alkali-hydrolyzed nitrogen, and Olsen-P content in both the topsoil (0–20 cm) and subsoil (20–40 cm), but not with available potassium in the soil. Therefore, conducting soil tests and determining fertilizer recommendations based on the proposed RF method at harvest can reduce fertilizer usage and achieve a balance between the conflicting objectives of environmental protection, increased crop yields, nutrient utilization efficiency, and improved economic benefits in oasis agricultural areas facing excessive fertilizer application.

In a low-input agricultural context, plants facing temporal nutrient deficiencies need to be efficient. By comparing the effects of NOFormula-starvation in two lines of Arabidopsis thaliana (RIL282 and 432 from the Bay-0xShahdara population), this study aimed to screen the physiological mechanisms allowing one genotype to withstand NOFormula-deprivation better than another and to rate the relative importance of processes such as nitrate uptake, storage, and recycling. These two lines, chosen because of their contrasted shoot N contents for identical shoot biomass under N-replete conditions, underwent a 10 d nitrate starvation after 28 d of culture at 5 mM NOFormula. It was demonstrated that line 432 coped better with NOFormula-starvation, producing higher shoot and root biomass and sustaining maximal growth for a longer time. However, both lines exhibited similar features under NOFormula-starvation conditions. In particular, the nitrate pool underwent the same drastic and early depletion, whereas the protein pool was increased to a similar extent. Nitrate remobilization rate was identical too. It was proportional to nitrate content in both shoots and roots, but it was higher in roots. One difference emerged: line 432 had a higher nitrate content at the beginning of the starvation phase. This suggests that to overcome NOFormula-starvation, line 432 did not directly rely on the N pool composition, nor on nitrate remobilization efficiency, but on higher nitrate storage capacities prior to NOFormula-starvation. Moreover, the higher resistance of 432 corresponded to a higher nitrate uptake capacity and a 2–9-fold higher expression of AtNRT1.1, AtNRT2.1, and AtNRT2.4 genes, suggesting that the corresponding nitrate transporters may be preferentially involved under fluctuating N supply conditions.

• In wheat the period of grain filling is characterized by a transition for all vegetative organs from sink to source status. • To study this transition, the progression of physiological markers and enzyme activities representative of nitrogen metabolism was monitored from the vegetative stage to maturity in different leaf stages and stem sections of two wheat (Triticum aestivum) cultivars grown at high and low levels of N fertilization. • In the two cultivars examined, we found a general decrease of the metabolic and enzyme markers occurred during leaf ageing, and that this decrease was enhanced when plants were N-limited. Both correlation studies and principal components analysis (PCA) showed that there was a strong relationship among total N, chlorophyll, soluble protein, ammonium, amino acids and glutamine synthetase (GS) activity. • The use of a marker such as GS activity to predict the N status of wheat, as a function of both plant development and N availability, is discussed with the aim of selecting wheat genotypes with better N-use efficiency.

Internal nitrogen (N) storage and remobilization processes support seasonal growth (flowering/fructification and subsequent leaf development) in particular in early spring, when soil temperatures are unfavourable for adequate N uptake. Storage nitrogen mobilization in young citrus trees was studied under two contrasting N supplies; high N (HN) and low N dose (LN) in the critical period of flowering and fruit set. N-15 labelling technique was used to distinguish N derived from internal remobilization from that taken up by the roots. Regardless N supply, the greatest N remobilization took place from the beginning of the vegetative activity until flowering. Low N availability significantly increased (+14%) N retranslocation at the end of June drop agreeing with the hypothesis that reserve mobilization depends on soil N availability during flowering and fruit set. At the end of fruit drop, N remobilization contributed up to 70% and 61% of total N of young organs for LN and HN, respectively. Remobilized N was mainly recovered in abscised organs of both HN and LN trees and to a lesser extent in new flush leaves; however a greater percentage partitioned to abscised organs of LN as a consequence of the greater remobilization rate and the increased fruit abscission. Old leaves of LN remobilized significantly higher N, while woody organs and root system did not show differences between HN and LN supplied trees. The results presented in this paper demonstrate that the amount of N remobilized by young citrus plants depends on external N availability. Thus, low N application rates in early stages (flowering and fruit set) lead to higher translocation of N stored during the previous cycle to developing new organs.