Higher Leaf Research Articles

Leaf nitrogen and phosphorus resorption efficiencies are related to drought resistance across woody species in a Chinese savanna.

Leaf nutrient resorption and drought resistance are crucial for the growth and survival of plants. However, our understanding of the relationships between leaf nutrient resorption and plant drought resistance is still limited. In this study, we investigated the nitrogen and phosphorus resorption efficiencies (NRE and PRE), leaf structural traits, leaf osmotic potential at full hydration (Ψosm), xylem water potential at 50% loss of xylem-specific hydraulic conductivity (P50) and seasonal minimum water potential (Ψmin) for 18 shrub and tree species in a semiarid savanna ecosystem, in Southwest China. Our results showed that NRE and PRE exhibited trade-off against drought resistance traits (Ψosm and P50) across woody species. Moreover, this relationship was modulated by leaf structural investment. Species with low structural investment (e.g., leaf mass per area, leaf dry mass content and leaf construction cost [LCC]) tend to have high NRE and PRE, while those with high LCCs show high drought resistance, showing more negative Ψosm and P50.These results indicate that species with a lower leaf structural investment may have a greater need to recycle their nutrients, thus exhibiting higher nutrient resorption efficiencies, and vice versa. In conclusion, nutrient resorption efficiency may be a crucial adaptation strategy for coexisting plants in semiarid ecosystems, highlighting the importance of understanding the complex relationships between nutrient cycling and plant survival strategies.

Decomposition of litter mixtures induces non-additive effects on soil priming across a riparian land use gradient

While litter traits have been used for decades to predict decomposition rates through the Leaf Economics Spectrum (LES) acquisitive to conservative trait lens, litter trait and litter mixture effects on soil carbon (C) priming effects (PE) is less known. To assess whether the LES can predict soil C PE during the decomposition of litter mixtures from complex ecosystems, a 99-day incubation experiment was conducted. The experiment involved soil and leaf litter from three Canadian riparian land uses (grasslands, deciduous agroforests, and coniferous agroforests), incubated as single plant species, and as plant species mixtures in their natural proportions. Natural abundance δ13C-isotopic analysis was used to assess the proportion of CO2 derived from leaf litter versus soil C mineralization at initial (0–21 days, stage I) and later (22–99 days, stage II) stages of decomposition. Single species positions on the LES mirrored litter-C mineralization dynamics, yet PE emissions remained harder to predict with LES traits. Nonetheless, higher PE emissions relative to litter-C mineralization were observed with litter from LES species expressing conservative traits compared to LES species expressing acquisitive traits. Leaf litter mixtures from both agroforests, expressing high leaf litter trait functional dissimilarity, resulted in synergistic, non-additive effects on soil PE. These findings contribute to our understanding of the effects of leaf litter functional traits and trait mixing on soil PE, highlighting that mixed-species litter decomposition can lead to non-additive effects on soil C dynamics in forested riparian ecosystems.

Drought‐tolerant grassland species are generally more resistant to competition

Abstract Plant populations are limited by resource availability and exhibit physiological trade‐offs in resource acquisition strategies. These trade‐offs may constrain the ability of populations to exhibit fast growth rates under water limitation and high cover of neighbours. However, traits that confer drought tolerance may also confer resistance to competition. It remains unclear how fitness responses to these abiotic conditions and biotic interactions combine to structure grassland communities and how this relationship may change along a gradient of water availability. To address these knowledge gaps, we estimated the low‐density growth rates of populations in drought conditions with low neighbour cover and in ambient conditions with average neighbour cover for 82 species in six grassland communities across the Central Plains and Southwestern United States. We assessed the relationship between population tolerance to drought and resistance to competition and determined if this relationship was consistent across a precipitation gradient. We also tested whether population growth rates could be predicted using plant functional traits. Across six sites, we observed a positive correlation between low‐density population growth rates in drought and in the presence of interspecific neighbours. This positive relationship was particularly strong in the grasslands of the northern Great Plains but weak in the most xeric grasslands. High leaf dry matter content and a low (more negative) leaf turgor loss point were associated with high population growth rates in drought and with neighbours in most grassland communities. Synthesis: A better understanding of how both biotic and abiotic factors impact population fitness provides valuable insights into how grasslands will respond to extreme drought. Our results advance plant strategy theory by suggesting that drought tolerance increases population resistance to interspecific competition in grassland communities. However, this relationship is not evident in the driest grasslands, where above‐ground competition is likely less important. Leaf dry matter content and turgor loss point may help predict which populations will establish and persist based on local water availability and neighbour cover, and these predictions can be used to guide the conservation and restoration of biodiversity in grasslands.

Assessment of the Air Cleaning Performance and Humidity and Temperature Control by Five Evergreen Woody Plants

Indoor air quality (IAQ) directly affects human health. The increase in PM and CO2 concentration indoors caused an increase in the prevalence of sick building syndrome (SBS) symptoms. Plants could contribute to reducing particulate matter (PM) and CO2. This study identifies the most efficient evergreen plant species for improving indoor air quality by assessing the ability of five different indigenous Korean evergreen plant species to reduce PM and CO2 and regulate humidity and temperature under indoor environmental conditions in acrylic chambers. The clean air delivery rates (CADR) were calculated to evaluate the efficacy of plants in reducing PM and CO2. We assessed the performance of removing the five study plants on PM1 (~0.68–3.01 m3/h/leaf area), PM2.5 (~0.73–3.08 m3/h/leaf area), PM10 (~0.67–3.04 m3/h/leaf area), and CO2 (~0.48–1.04 m3/h/leaf area). The species Ilex pedunculosa, Pittosporum tobira, and Gardenia jasminoides were the most effective at reducing PM. The CADR of CO2 also differed among the five plant species and corresponded to their photosynthetic rate. Viburnum odoratissimum var. awabuki, which had the high photosynthetic rate, was most effective at reducing CO2. By contrast, PM reduction was correlated with plant leaf structure. Plants with a high leaf density can accumulate more PM. The plants were also able to control temperature and humidity. The average temperature of the control chamber was higher, and the humidity was lower than that of the plant chambers. In this study, the five evergreen species effectively reduced air pollutants and can be used to improve IAQ.

Climatic differentiation: Variability in leaf functional and stoichiometry traits among different woody species in semi-arid forests

Structural and nutrient traits of foliage are important for understanding plant ecological strategies. Understanding structural variations of trees in different environmental conditions helps to reveal adaptation mechanisms. We investigated morphological, chemical and stoichiometric traits in the foliage of four dominant woody species in sub-humid vs. semi-arid of the Zagros forests, west of Iran. Dry matter content, specific leaf area (SLA), stomatal length (SL), stomatal width (SW), density (SD) and stomatal pore index (SPI) traits were higher in the trees growing in a sub-humid climate. In Pistacia atlantica (PA) growing in the semi-arid climate, leaf length, SLA, SD and SPI traits were higher than the sub-humid climate. Leaf phosphorus content of Crataegus aronia (CA) was higher in the sub-humid, whereas PA was higher in the semi-arid climate. In PA and CA, the highest leaf C: P and N: P were in the sub-humid and the semi-arid climate. The relationship between SLA and leaf carbon content was significantly negative in PA. Among the different species, carbon content, nitrogen and phosphorus and their stoichiometry had strong positive and negative relationships in two climates. These results show the response of leaf functional traits to climate changes and how trees function under these changes. Furthermore, the leaf traits showing greater variability due to changes in the environmental can be determined. This improved understanding will assist in determining the most important adaptive parameters of trees to climate changes, to provide inputs to global environmental models.

The Effect of the Combining Ability using the Second Generation According to Factorial Mating System in Durum Wheat

This study was carried out by evaluating the second generation of ten genotypes of coarse wheat, six (male parents) of which were obtained by ICARDA (Maggy, Zeina2, Joudille, Gigamar Lcarasha2, Adnham) and three adopted category (female parents) (Svevo, Grecale, Duma-1). In addition to a additive genotype * (Sardar), which was previously cultivated within the environmental conditions of the region and proved its distinction, these genotypes were planted with second generation hybrids, which numbered (24 hybrids) in the season (2021-2022) in the Bashiqa region of the city of Mosul, using the randomized complete block design. (R.C.B.D) with three replications. The study included the qualities : number of days to flowering at 50%, plant height (cm), spike length (cm), high leaf area (cm2), number of grains in a spike, number of spikes/m2, biological yield (kg/h), yield Cereals (kg/h), harvest guideline %, weight of 1000 grains, and protein percentage %. The data of the hybrids were analyzed according to the factorial panmixis method. analysis table showed variance for the mean squares of the hybrids that they were significant at the level of probability (1%) for all the studied qualities except for the characteristic of the biological yield. Significantly, at the probability level (5%), the male father (Duma-1) was superior in the effect of its general ability to joint the characteristics of plant height, spike length, high leaf area, number of spikes / m2, biological yield, grain yield, harvest guideline, weight of 1000 grains, and protein percentage. Showed Hybrid (Maggy x Sardar) specific effects to the desired direction for most of the qualities studied.

Molecular diversity of Protura in southern High Appalachian leaf litter.

The higher elevations of the southern Appalachian Mountains, U.S.A., host a rich, but little-studied fauna of Proturan hexapods. Here, we publish 117 Proturan barcode sequences from this region, estimated by automated species delimitation methods to represent 72 distinct species, whereas only nine species have previously been reported from the region. Two families, Eosentomidae and Acerentomidae, co-occur at most sampling sites, with as many as five species occurring in sympatry. Most populations exhibit very low haplotype diversity, but divergences amongst populations and amongst closely-related species are very high, a finding common to other phylogeographic studies of Proturans. Though we were unable to identify any of the barcodes to species, they form a useful, if preliminary, glimpse of southern Appalachian Proturan diversity.

Inverse priority effects: The order and timing of removal of invasive species influence community reassembly

Abstract An ongoing restoration challenge is to recover native communities after the removal of invasive species. Because priority effects (i.e. the order and timing of species arrival) can strongly determine the trajectory of community assembly, their intentional manipulation is gaining attention to manage invasive plants and achieve restoration goals. Yet, ecologists and conservationists rarely consider how the order and timing of species removal—inverse priority effect—may impact future plant communities. Here, we evaluated the dependence of community reassembly on inverse priority effects by experimentally removing the target invasives Sweetbriar rose (Rosa rubiginosa) and Scotch broom (Cytisus scoparius) in field and mesocosm communities. We manipulated removal order (rose before broom vs. broom before rose) and timing (simultaneously early vs. simultaneously late in the season). We performed a hierarchical modeling of species sommunity to assess differences in community structure in response to order and timing of removal, and to evaluate whether species origin and leaf and seed traits were associated with species responses. We found that the order of removal was as important as timing driving community reassembly. Simultaneous removal favoured nonnatives, more so when performed early. Sequential removals led to contrasting communities. Rose before broom removal also favoured nonnative grasses at expense of native species, whereas the inverse order produced small changes in communities. In general, species with high specific leaf area were boosted, regardless of their seed size. Synthesis and applications. Inverse priority effects are neglected mechanisms that can drive variability in the reassembly of plant communities and can potentially upgrade invasive species management. These historical contingencies suggest the existence of an optimal order of removal that facilitates the recovery of the native community. We found that simultaneous removal promoted secondary invasions to a greater extent than sequential removals. Furthermore, removal order affected post‐removal community structure. In our system, we suggest removing the rose before the broom to hinder nonnatives and pave the way for restoration of native communities. Our results show that manipulation of the order and timing of removal can help to achieve restoration goals.

Impact of Cucurbita moschata Resistant Rootstocks on Cucumis sativus Fruit and Meloidogyne incognita Development.

Plant grafting can provide resistance to nematodes. There is a distinct need to determine the role of Meloidogyne incognita-resistant rootstocks on the growth and quality of grafted cucumber plants. Cucumber (Cucumis sativus L.) cultivar Jinchun No. 4 (J) was hole grafted onto the pumpkin (Cucurbita moschata) cultivars Xiuli (X), Banzhen No. 3 (B), and its root to generate JX, JB, and JJ plants. The histopathology and M. incognita development associated with JX, JB, and JJ were analyzed under incubator and high plastic tunnel conditions. Under incubator conditions, M. incognita root galls and egg mass indices associated with the JX and JB resistant rootstocks were significantly (P < 0.05) lower than those associated with JJ susceptible rootstocks. In addition, the number of eggs were 73.3 ± 8.8% and 85.3 ± 7.7% less, respectively. The number of second-stage juveniles (J2s) in JX roots decreased by 57.1 ± 9.2% compared with that in JJ, and the giant cell and J2 development were poor in JX and JB roots. In pot experiments under a high plastic tunnel, plant height, stem diameter, leaf area, and yield of M. incognita-infected JX plants were not significantly different from those of noninoculated control. There was no significant difference in fruit weight, length, firmness, soluble solids, and color among the three grafted plants. The yield per JB plant was increased compared with that of JJ, irrespective of nematode presence. In the M. incognita-infested soil experiment in a high plastic tunnel, the yield per JX and JB plant were significantly higher than JJ (P < 0.05). Thus, the pumpkin rootstock Xiuli and Banzhen No. 3 are promising rootstocks for managing M. incognita without affecting cucumber fruit quality. Grafting provides a good basis for studying the defense mechanism of rootstocks against M. incognita.

Shoot Flammability Patterns in Native and Exotic Street Tree Species at the Wildland–Urban Interface of Eastern Australia

Street trees provide ecosystem services such as heat mitigation, improved community well-being, and biodiversity conservation. At the wildland–urban interface (WUI), high-flammability street trees also provide a conflicting ecosystem disservice, heightening risks of wildfire spread into urban areas. We addressed this service–disservice conflict by assessing shoot flammability patterns in 10 street tree species, to identify low-flammability species that can potentially mitigate wildfire risks at the WUI. We found significant differences among species in flammability attributes including time-to-flame (TTF), flame duration (FD), number of flaming events (nF), and flame temperature (FT), and identified low-flammability species for each attribute. Overall, species’ rankings from least to most flammable differed considerably across the four attributes. For example, native water gum (Tristaniopsis laurina) had the slowest TTF, but had the longest FD. Among nine shoot traits, we found that high leafing intensity was the most frequent trait correlated with flammability. In particular, high leafing intensity was significantly related to fast TTF and high FT. Lack of coordination among flammability attributes suggests that, in general, selection of low-flammability street tree species should consider how each flammability attribute differentially contributes to wildfire spread risk. Nonetheless, native Tuckeroo (Cupaniopsis anacardioides) emerged as a potential candidate for further exploration as a low-flammability street tree as it had comparatively long TTF, short FD, and low nF. We found no consistent evidence that exotic species were less flammable than native species, and suggest that native trees be the focus of further research to identify low-flammability street trees.

Variation in rapeseed genotype’s reaction to drought during flowering and identification of tolerant-genotypes selection index

Rapeseed (Brassica napus L.) crop is particularly susceptible to drought at the flowering stage. This study was conducted to (i) assess four genotypes under contrasting water conditions for their reaction to drought and (ii) determine the traits associated with tolerance and yield stability. The experiment was carried out in pots during two cropping years under greenhouse-controlled conditions. From the flowering stage to early seed maturity, the four genotypes were evaluated under two levels of water stress T2 (66% of T1) and T3 (33% of T1), in addition to full irrigation as the control water regime (T1). Results indicated significant effects of genotype, water regime and their interaction on all measured parameters. The genotype ‘Nap9’ was the best regarding seed yield and oil content under the two levels of water stress and for both years. It also exhibited higher root length and higher leaf relative water content than the other genotypes. Therefore, it may be recommended as a valuable germplasm in rapeseed breeding programs for drought tolerance. High branching combined with high leaf relative water content could be a relevant and valuable selection index for this breeding program.

Temporal shifts in the functional composition of Andean forests at different elevations are driven by climate change

AbstractAimAndean forests are a global biodiversity hotspot. They harbour many species living within narrow climate ranges and a high functional diversity of trees. It remains still unclear how such hotspots respond to climatic changes over time. We investigated whether Andean forests are changing their functional composition over time along an elevational gradient by assessing changes in species composition, abundance and functional traits.LocationAn elevational gradient in Colombia's northern Andes.Time PeriodSpecies composition changes were studied two to four times from 2006 to 2017, and functional composition from 2016 to 2017.Major Taxa StudiedA total of 1104 tropical tree species with in situ traits characterization.MethodsWe used seven morphological leaf traits and wood density values to analyse the functional trait dynamic over 10 years along an elevational gradient. By analysing changes in species composition, abundance and trait representation, we inferred the magnitude and direction of changes in functional composition. Then, we assessed if the functional change was related to climate change and demography.ResultsWith increased minimum temperature and vapour‐pressure deficit, we found a decrease over time in mean values for leaf area and specific leaf area and increases in leaf thickness and leaf dry matter content. Long‐term temperature increases are smaller with increasing elevation, but the magnitude of trait changes is greater than in lowlands.Main ConclusionsThe functional composition is changing towards more conservative strategies over time across the elevation gradient, with the strongest changes observed at the highest elevations. This pattern is explained by the change in species turnover within communities due to higher recruitment rates of species with high leaf dry matter content values and low leaf area values. These shifts may be related to communities' responses to higher evapotranspiration demand and thermal stress, mainly at higher elevations.

A test of island plant syndromes using resource‐use traits

AbstractDespite representing a fraction of the global terrestrial surface area, oceanic islands are disproportionately diverse in species, resulting from high rates of endemicity. Island plants are thought to share a unique phenotype—referred to as an island syndrome—which is thought to be driven by convergent evolution in response to selection by shared abiotic and biotic factors. One aspect of the island plant syndrome that has received relatively little research focus is that island plants are expected to have converged on conservative resource use associated with slow growth rates and weak competitive abilities. Here we tested whether native, woody Hawaiian plant species are phenotypically distinct—with more resource‐conservative leaf traits—compared to a globally distributed sample of continental species. Using an archipelago‐wide trait data set, we detected that on average, native Hawaiian species had lower leaf nutrient concentrations overall, and lower nutrient concentrations at high leaf mass per area, but no other phenotypic differences compared with continental plants. There was also considerable overlap in the trait spaces of native Hawaiian species and continental species. Our findings indicate that an island plant syndrome for leaf traits is not present in the Hawaiian flora, and that island species can demonstrate extensive variation in their resource‐use strategies, on a scale that is comparable with that of continental species worldwide.

The role epiphytes play in particle capture of seagrass canopies

Seagrass epiphytic communities act as ecological indicators of the quality status of vegetated coastal environments. This study aims to determine the effect leaf epiphytes has on the sediment capture and distribution from outside sources. Thirteen laboratory experiments were conducted under a wave frequency of 0.5 Hz. Three epiphyte models were attached to a Zostera marina canopy of 100 plants/m2 density. The sediment deposited to the seabed, captured by the epiphytic leaf surface, and remaining in suspension within the canopy were quantified. This study demonstrated that the amount of epiphytes impacts on the sediment stocks. Zostera marina canopies with high epiphytic areas and long effective leaf heights may increase the sediment captured on the epiphyte surfaces. Also, reducing suspended sediment and increasing the deposition to the seabed, therefore enhancing the clarity of the water column. For largest epiphytic areas, a 34.5% increase of captured sediment mass is observed. The sediment trapped on the leaves can be 10 times greater for canopies with the highest epiphytic areas than those without epiphytes. Therefore, both the effective leaf length and the level of epiphytic colonization are found to determine the seagrass canopy ability at distributing sediment.

Changes in Leaf Functional Traits Driven by Environmental Filtration in Different Monsoon Tropical Forest Types

Disturbances have created heterogeneous habitats for secondary and old-growth forests. Under the assumption that ecologically similar species have similar functional traits, numerous studies have attempted to use trait-based approaches to infer the abiotic and biotic factors that drive variations in community composition across different forests. However, the relative importance of these drivers in monsoon forests remains poorly understood. In this study, we randomly selected 86 plots and classified them into three forest types according to environmental factors: 1—secondary forests: secondary forest habitats at high elevation; 2—ecotone forests: general recovery and elevation; and 3—old growth forests: old growth at low elevations. We then compared the species and six leaf functional trait variations across the three forests and assessed their relationships with 15 environmental factors. The results showed that secondary and ecotone forests with a conservative strategy, exhibiting high dry matter content and leaf carbon content, tended to persist in stressful habitats, such as nutrient-poor soil, whereas old growth forests invested in trait values related to rapid resource acquisition with high specific leaf area, leaf nitrogen content, leaf phosphorous content, and leaf potassium content. Species with functional trait values between the secondary, ecotone, and old growth forests had clear signatures of their different strategies to persist in assemblages under distinct and opposite environmental filters. These plots were classified into three forest types according to environmental factors: (1) secondary forest at high elevation; (2) ecotone forests at general elevation; and (3) old growth forests at low elevation. Recovery time and elevation, followed by soil nutrients and light capture, were the most important factors shaping species and functional trait variations across forests. These results have demonstrated that environmental filters select plant species with distinct traits and ecological strategies. Acquisitive traits indicate higher competitive ability and faster resource acquisition for forest species that occur in areas with high soil fertility. Meanwhile, conservative traits promote the resistance of secondary species to environmental stressors in low soil fertility, suggesting that analyzing leaf functional-based trait variations to understand plant ecological strategies along an environmental gradient may improve understanding of forest dynamics in tropical monsoon forests.

Use of Satellite-based Leaf Area Index Data for Monitoring Green Gram Crop Growth in Ikombe-Katangi Area, Machakos County, Kenya

Monitoring the conditions under which crops grow and estimating their yield is essential to the process of economic development in any nation. The traditional approaches to crop monitoring are labor- and resource-intensive, as well as limited in their ability to cover expansive geographic regions. Since remote sensing data is integrated with ground measurements, it has been used as a potentially useful tool to extract biophysical variables such as leaf area index (LAI), biomass, and phenology. Leaf Area Index (LAI) is a key variable that bridges remote sensing observations to the quantification of agroecosystem processes such as yield. The potential of satellite-based LAI for monitoring crop growth was investigated and compared to field measurements. This was the objective of his study. High resolution leaf area index was retrieved from Landsat 8 OLI imageries, and ground leaf area index measurements were taken in Ikombe-Katangi Machakos in Machakos county. An equation based on regression was developed to estimate the leaf area index using the normalized difference vegetation index that was derived from Landsat-8 OLI (NDVI). According to the findings, the derived LAI exhibited strong linear relationships with the leaf area index that was measured on the ground for green gram crops, with RMSE values being 0.09846, and R2 values of 0.9249. The overall findings shed light on the viability of using multispectral data, in estimating leaf area index in a very fragmented agricultural landscape, such as that found in the Ikombe and Katangi areas of Machakos, Kenya. Therefore, accurate crop monitoring on a large scale can be accomplished through remote sensing data in conjunction with LAI measurements taken from the ground. The implementation of the leaf area index is subject to the environmental condition which requires to be investigated as the use of remote sensing data is advocated for. The advancement in the use of satellite data for extraction LAI data is key towards transforming crop production within Kenya ad Africa at large. Scarce resources for crop growth monitoring can now be augmented with open-source satellite datasets such as Landsat 8 in LAI estimation.

Climatic variability and plant functional traits in tropical montane cloud forest refugia along the Trans Mexican Volcanic Belt

Functional traits represent the adaptive responses of plant species to climatic changes. They are an integrative marker of the general environmental conditions at a location. Testing their patterns may help to understand how the functional traits would track these environmental changes of tropical montane cloud forests (TMCFs). These forests are characterized by the constant presence of clouds, and these are among the most threatened ecosystems by climate change worldwide. One of the main TMCF regions in Mexico is the Trans-Mexican Volcanic Belt (TMVB). This region has provided refugia during past climate-change events. We identify three current regions of distribution of TMCF in TMVB, Pacific, Center and Gulf. We used 60 years of climatic information, functional traits and plants databases. We proposed the following aims: to determine whether changes in climatic variation have occurred in the TMVB and how these changes can be related to functional trait variations for dominant tree species across the three TMCF regions, and to know the potential changes as a refuge of the TMCF of the TMVB. We found different rainfall and maximum temperature patterns among and within regions. We identified that the Pacific region forests were characterized by the lowest specific leaf area (SLA), wider leaf thickness and high leaf density, which indicates resources-conservative leaf economics and tolerance to low humidity. Center and Gulf forests were distinguished by the highest SLA, less leaf thickness, and higher leaf density values, which suggests that the leaves of dominant tree species tend to be resources-acquisitive rather than conservative-resources. Finally functional traits were associated with prevailing climatic conditions and suggested that SLA, leaf thickness and leaf density are the main functional traits that could be used to relate them to regional climate. Also, Central and Gulf regions could serve as a refuge for those species of trees demanding humidity.

Evaluation of Maize Varieties at Seedling Stage under Drought Stress Based on Morpho-physiological and Biochemical Attributes

A hydroponic pot experiment was driven to investigate the improvement of drought tolerance in six maize varieties (e.g. Gold Star, BHM 14, Paloan, Bharti 981, BHM 9, Pioneer) based on morpho-physiological and biochemical characteristics. Six Maize varieties were used as test crops and the experiment was laid out in a completely randomized design (RCBD) with three replications. Drought stress was imposed 14 days after sowing by using the PEG solution. The results revealed that BHM 14 possessed the longest root length (69.33 cm), higher shoot length (42.67 cm), longest total plant height (112.00 cm), highest fresh root weight (3.32 g), high leaf greenness found in BHM 14 measured by SPAD meter in both top and lower leaves, high amount of proline whereas, Paloan produced shortest total plant height (78.50 cm), lowest fresh root weight (1.52 g), lowest proline after 42 days of sowing under stress condition. The maximal photochemical efficiency (Fv/Fm) appeared to measure photosynthesis whereas Pioneer was comparatively higher in stress conditions. The fresh weight of root and shoot was significantly least affected in stress conditions, whereas BHM 14 performed better in stress conditions. On the other hand, varieties had a significant difference in total dry matter of control condition and stress condition. Therefore, it is suggested that BHM 14 showed maximum drought tolerance in respect of growth and morpho-physiological changes under drought conditions.

Partial Resistance Components and Morphological Traits Aid Selection of Resistant Wheat Genotypes against Spot Blotch

Spot blotch caused by Bipolaris sorokiniana results substantial yield losses (15-80%) in an Indian subcontinent. Wheat varietal improvement through breeding followed by evaluation of elite germplasms against a particular disease is crucial method to manage diseases. Fifty diverse wheat genotypes and two susceptible checks viz., Sonalika and Nepal 297 were evaluated under artificial epiphytotic condition against spot blotch at NWRP, Bhairahawa, Nepal in 2017-18 and 2018-19. Evaluation was based on partial resistance components viz., lesion sizes, lesion types (chlorotic/ necrotic), lesion characteristics (sporulating/ non-sporulating) and area under disease progress curve (AUDPC) and morphological traits viz. lesion mimic, leaf angle, leaf tip necrosis and plant height. Statistical analysis revealed that genotypes with smaller lesion size (&lt;1 cm), small dark brown to black lesions with or without chlorosis/ necrosis and non sporulating lesions had lower AUDPC (&lt;225). Similarly genotypes with erect to semi erect leaf (leaf angle 1-2), medium to high leaf tip necrosis (2-4), low percentage of lesion mimic (0-22.5%) were found resistant (AUDPC&lt;225) to moderately resistant (AUDPC value 226-315). Moreover AUDPC showed strong and positive correlation with lesion sizes (0.76), lesion types (0.84) and lesion characteristics (0.54). Twenty genotypes were found resistant (AUDPC&lt;225), could be used as new resistance sources in breeding program. However genotypes viz., KACHU/BECARD//WBLL1*2/BRAMBLING/3/ATTILA*2/PBW65//MURGA, FRET2*2/SHAMA//TNMU/3/FRET2*2/SHAMA/4/UP2338*2/KKTS*2//YANAC/5/FRET2*2/SHAMA//PARUS/3/FRET2*2/KUKUNA, KACHU#1//PI610750/SASIA/3/KACHU/4/MUU#1//PBW343*2/KUKUNA/3/MUU/5/KACHU#1//PI610750/SASIA/3/KACHU, BORL14//KFA/2*KACHU and KFA/2*KACHU//QUELEA were found excellent based on partial resistance components and morphological traits. These genotypes could be further evaluated for yield potential in multi environment and better performing genotypes could be released as resistant varieties for spot blotch.

Seasonal Regulation of Soil Microbial Carbon and Phosphorus Metabolisms in an Apple Orchard: Evidence from the Enzymatic Stoichiometry Method

Soil microbial carbon (C), nitrogen (N), and phosphorus (P) nutrient requirements and metabolic limitations are closely related to the availability of environmental nutrients. However, it is unclear how manure and chemical fertilization shift nutrient limitations for microbes in terms of the soil enzymatic stoichiometry in an apple orchard. Therefore, based on the long-term experiment located in an apple orchard established in 2008, this study applied the theory and method of soil enzyme stoichiometry to systematically investigate the effects of the combined application of manure and chemical fertilizers on soil C, N, and P turnover-related enzyme activities (β-1,4-glucosidase, BG; leucine aminopeptidase, NAG; β-1,4-N-acetylglucosaminidase, LAP; and acid or alkaline phosphatase, PHOS) and their stoichiometric characteristics and analyzed their relationships with environmental factors and microbial carbon use efficiency. The experiment was designed with four treatments, such as, no fertilization input as the control (CK), single application of chemical fertilizer (NPK), combined application of manure and chemical fertilizer (MNPK), and single application of manure (M). The results revealed that:① at different growth stages of fruit trees, the soil microbial biomass C (microC) content of manure fertilizer treatments (MNPK and M) was significantly higher than that of no manure fertilizer treatments (CK and NPK). The content of microbial biomass N (microN) in the NPK, MNPK, and M treatments increased by 89%, 269%, and 213%, respectively, compared with that in CK (P<0.05). ② Compared with those in the fertilization treatments, CK had higher leaf N and P contents (29.8 g·kg-1 and 2.17 g·kg-1) at the germination stage, and the leaf P content at the germination stage alone was significantly negatively correlated with soil available phosphorus (AP) content. ③ Soil enzyme stoichiometry analysis demonstrated that all data points in this study were above the 1:1 line, indicating that microbial communities had a strong phosphorus limitation. The range of vector length and angle was 0.56-0.79 and 59.3°-67.7°, respectively, in the growth period of fruit trees, and the vector angle was >45° in this study, which also reflected the strong phosphorus limitation of microorganisms. ④ RDA and random forest model analysis showed that organic carbon and available nitrogen (AN) were the main physical and chemical factors affecting vector length; AP, AN, and soil water content were the main physical and chemical factors affecting vector angle. Combined with SEM analysis, AN and dissolved organic carbon (DOC) directly affected microC and microN, AP directly affected microP and microN, DOC and AP directly affected vector length, and AP and microN directly affected vector angle. In addition, microbial carbon utilization was positively correlated with vector length and negatively correlated with vector angle. In summary, the combined application of manure and chemical fertilizers regulated microbial carbon and phosphorus metabolism by affecting soil carbon and phosphorus content at different growth stages of fruit trees, thereby affecting microbial carbon utilization. This study provides a scientific basis for manure and chemical fertilizers to improve soil quality and maintain soil health.