Identification of candidate genes and residues for improving nitrogen use efficiency in the N-sensitive medicinal plant Panax notoginseng

Morphophysiological and proteomic profiling unveiling mechanisms underlying nitrogen use efficiency in popcorn (Zea mays var. everta)

In this study we hypothesize that the contrasting nitrogen use efficiency (NUE) between popcorn (Zea mays var. everta) inbred lines P2 (high NUE) and L80 (low NUE) is driven by distinct morphophysiological responses and proteomic profiles found in leaves and roots. To elucidate the mechanisms involved, plants were cultivated in a greenhouse under high (100% N) and low (10% N) nitrogen conditions, in a randomized complete block design with two factorial treatment arrangements and seven blocks. Morphological and physiological traits such as photochemical and non-photochemical quenching, quantum yield of photosystem II, and potential photosynthesis were evaluated. Compared to L80, under low N, P2 exhibited 25.9% greater leaf area, 22.4% taller plants, 21.7% thicker stems and 113% higher shoot dry mass, as well as higher values of photochemical and non-photochemical quenching and quantum yield of photosystem II that drove to a maximum photosynthesis 16.5% higher than L80. Comparative proteomic analysis of the leaves identified 215 differentially accumulated proteins (DAPs) in P2 and 168 DAPs in L80, while in roots, 127 DAPs were observed in P2 and 172 in L80. Notably, in leaves, the response to oxidative stress, energy metabolism, and photosynthesis represented the main differences between P2 and L80. In roots, the nitrate transport, ammonium assimilation, and amino acid metabolism appear to have contributed to the improved NUE in P2. Consequently, this study provides valuable insights into the molecular mechanisms underlying NUE and opens avenues for molecular breeding aimed at selecting superior genotypes for the development of a more sustainable agriculture.

Role of nitrogen amendments on carbon fixation efficiency of ozone exposed lemongrass: Interrelationship between secondary metabolite production and yield

The phytotoxic nature of Ozone (O3) has been well documented in a number of scientific literatures during the last few decades. Although there are sufficient studies related to O3 impact assessment studies on crop plants and tree species, studies pertaining to O3 effects on medicinal plants are comparatively sparse. During the recent years, the mitigation strategies for management of O3 stress in plants have also assumed paramount significance. The present study sought to explore the combined impact of soil nitrogen (N) amendments and O3 doses on morphological and physiological responses, and metabolite profile of lemongrass, an aromatic medicinal plant. The experiment utilised three levels of inorganic soil N amendments within Open Top Chambers, subjected to ambient (A) and two elevated O3 doses. For each O3 treatment, control was also maintained, wherein no N amendments were done. The objective of the study was to study the pattern of allocation of carbon pool towards biomass accumulation and secondary metabolite production under N amendments and O3 exposure conditions in lemongrass. The results of the physiological traits clearly suggest the resurgence of the photosynthetic machinery of O3 exposed lemongrass. The improved response of the carbon fixation processes upon N amendments resulted in supplemented carbon pool, diverting it towards increased biomass accumulation and yield of lemongrass, which was depreciated under O3 stress. This study demonstrates that N amendments in O3 stressed lemongrass enhance bioactive compound production, and sustain yield. Further researches are required to establish optimal N doses under varying O3 conditions, potentially advancing pharmaceutical applications of O3 exposed medicinal plants.

Deep application of controlled-release urea increases the yield and saponin content of Panax notoginseng by regulating soil nitrate distribution

Introduction

The deep application of controlled-release urea (CRU) offers potential advantages for crops with extended growth periods. However, its effects on P. notoginseng yield and quality, a medicinal plant with a prolonged nutrient acquisition duration, remain unclear.

Methods

In this study, we conducted a two-year field plot experiment to investigate the effect of CRU on P. notoginseng with three placement depths (0, 6, and 12 cm denoted as R0, R6, and R12, respectively) at an application dosage of 250 kg N ha-1 with biochar addition (R6B) and 20% N reduction (R6R) based on the R6, with conventional fertilization (250 kg N ha-1, common urea) serving as the control (CK).

Results

Our results indicated that yields increased by 27.1-37.6% with R0, R6, R12, and R6B, while remaining stable with R6R compared to CK. Simultaneously, the total saponin content in the roots of R6, R6B, and R6R was improved by 14.3-38.1%, compared to CK. The distribution depth of soil NO3 ⁻-N and plant roots increased with the depth of CRU application, with a high overlap in time and space, indicating P. notoginseng N uptake peaked when CRU was applied at a depth of 6 cm (R6). Structural equation modeling indicated that soil NO3 ⁻-N supply in specific microareas directly affected the N uptake and increased total saponin content by increasing root length and surface area, thus boosting yield.

Conclusion

This study identifies that the deep application of CRU at a depth of 6 cm has the potential to enhance both yield and quality of P. notoginseng and highlights that the spatial-temporal matching of soil NO₃⁻-N and plant roots was the key to applying CRU to ensure high yield and quality.

Investigation of morpho-physiolgical traits and gene expression in barley under nitrogen deficiency

Nitrogen (N) is an essential element for plant growth, and its deficiency influences plants at several physiological and gene expression levels. Barley (Hordeum vulgare) is one of the most important food grains from the Poaceae family and one of the most important staple food crops. However, the seed yield is limited by a number of stresses, the most important of which is the insufficient use of N. Thus, there is a need to develop N-use effective cultivars. In this study, comparative physiological and molecular analyses were performed using leaf and root tissues from 10 locally grown barley cultivars. The expression levels of nitrate transporters, HvNRT2 genes, were analyzed in the leaf and root tissues of N-deficient (ND) treatments of barley cultivars after 7 and 14 days following ND treatment as compared to the normal condition. Based on the correlation between the traits, root length (RL) had a positive and highly significant correlation with fresh leaf weight (FLW) and ascorbate peroxidase (APX) concentration in roots, indicating a direct root and leaf relationship with the plant development under ND. From the physiological aspects, ND enhanced carotenoids, chlorophylls a/b (Chla/b), total chlorophyll (TCH), leaf antioxidant enzymes such as ascorbate peroxidase (APX), peroxidase (POD), and catalase (CAT), and root antioxidant enzymes (APX and POD) in the Sahra cultivar. The expression levels of HvNRT2.1, HvNRT2.2, and HvNRT2.4 genes were up-regulated under ND conditions. For the morphological traits, ND maintained root dry weight among the cultivars, except for Sahra. Among the studied cultivars, Sahra responded well to ND stress, making it a suitable candidate for barely improvement programs. These findings may help to better understand the mechanism of ND tolerance and thus lead to the development of cultivars with improved nitrogen use efficiency (NUE) in barley.