Grass Research Articles

Some unique anatomical scaling relationships among genera in the grass subfamily Pooideae

Abstract Members of the grass family Poaceae have adapted to a wide range of habitats and disturbance regimes globally. The cellular structure and arrangements of leaves can help explain how plants survive in different climates, but these traits are rarely measured in grasses. Most studies are focused on individual species or distantly related species within Poaceae. While this focus can reveal broad adaptations, it is also likely to overlook subtle adaptations within more closely-related groups (subfamilies, tribes). This study therefore investigated the scaling relationships between leaf size, Vein Length Area (VLA), and vessel size in five genera within the subfamily Pooideae. The scaling exponent of the relationship between leaf area and VLA was -0.46 (+/- 0.21), which is consistent with previous studies. In Poa and Elymus, however, minor vein number and leaf length were uncorrelated, whereas in Festuca these traits were positively correlated (slope = 0.82 +/- 0.8). These findings suggest there are broad-scale and fine-scale variation in leaf hydraulic traits among grasses. Future studies should consider both narrow and broad phylogenetic gradients.

GRASSIUS 2.0: A gene regulatory information knowledgebase for maize and other grasses

Grass species, which include the major cereal crops maize, wheat, rice, and sugarcane, are an integral part of our global agriculture and source of food and energy for a growing world population. GRASSIUS was established as a knowledgebase for transcription factors (TFs) and coregulators (CoRegs) in maize and several other species in the grass family. TFs are a primary component of the gene regulatory networks (GRNs) and the underlying gene regulatory grids (GRGs) that govern all aspects of plant growth and metabolism. GRASSIUS is the source for all information pertaining to the maize TFome collection, which serves as a powerful resource for the discovery of GRNs in maize and other cereals [1,2]. Here we describe the release of the GRASSIUS 2.0 knowledgebase (www.grassius.org) with updated data, query, and tool features, as well as the ability to expand to accommodate future datasets. The membership and annotation of all TF and CoReg families has been updated and revised to include gene models from v3, v4, and v5, of the maize B73 genome and recent genome versions of rice, sorghum, Brachypodium, and sugarcane. A translation tool enables cross referencing of Gene IDs between versions of the maize genome. Protein-DNA interactions (PDIs) have been added incorporating results derived from various gene- and TF-centered PDI discovery tools and visualized through a new web-based interface. A filtering tools permits the selection and visualization of PDIs within a ± 2 kb distance from the transcriptional start site (TSS) of a gene of interest. A new BLAST (Basic Local Alignment Search Tool) tool facilitates searching of the maize TFome as well as v3, v4, and v5 TF gene model sets. Lastly, we describe the methodology used to implement GRASSIUS 2.0 which can guide others in developing and updating similar plant gene regulatory knowledgebases.

Microhabitat preferences in the European green lizard (Lacerta viridis): implications for conservation management of isolated populations

The European green lizard (Lacerta viridis) populations in Bohemia, Czech Republic, are isolated by more than 150 km from the northern border of the continuous range of the species. These populations are fragmented and further isolated from each other. In this landscape mosaic, they are tied to specific habitats located in deeply incised river valleys (the so-called river phenomenon) and thus may be viewed as stenotopic. The research site is located on the northern edge of the city of Prague. Since 1998, this site has been the subject of long-term conservation management aimed at strengthening and maintaining the abundance of the local L. viridis population. To formulate recommendations for the management of other isolated L. viridis populations, we performed a spatial analysis of the localities with observed individuals to determine and evaluate the significance of the chosen biotic and abiotic factors for habitat discrimination. We applied principal components and discriminant function analyses and examined the effect of 24 variables on the species’ presence. The results revealed the principal role of the presence of rock debris and hiding places for lizard occurrence. The strongest negative predictors were the presence of tall grass and high vegetation coverage. We discuss the applicability of our findings in both the theory and practice of species conservation and population management.

Bigger genomes provide environment-dependent growth benefits in grasses.

Increasing genome size (GS) has been associated with slower rates of DNA replication and greater cellular nitrogen (N) and phosphorus demands. Despite most plant species having small genomes, the existence of larger GS species suggests that such costs may be negligible or represent benefits under certain conditions. Focussing on the widespread and diverse grass family (Poaceae), we used data on species' climatic niches and growth rates under different environmental conditions to test for growth costs or benefits associated with GS. The influence of photosynthetic pathway, life history and evolutionary history on grass GS was also explored. We found that evolutionary history, photosynthetic pathway and life history all influence the distribution of grass species' GS. Genomes were smaller in annual and C4 species, the latter allowing for small cells necessary for C4 leaf anatomy. We found larger GS were associated with high N availability and, for perennial species, low growth-season temperature. Our findings reveal that GS is a globally important predictor of grass performance dependent on environmental conditions. The benefits for species with larger GS are likely due to associated larger cell sizes, allowing rapid biomass production where soil fertility meets N demands and/or when growth occurs via temperature-independent cell expansion.

Age- and Sex-Specific Differences in Lyme Disease Health-Related Behaviors, Ontario, Canada, 2015-2022.

We investigated differences in risk factors and preventive behaviors by age and sex among persons with reported Lyme disease in Ontario, Canada, during 2015-2022. Incidence rates peaked among children 5-9 and adults 50-79 years of age. Median age was higher for female than male case-patients (54 vs. 51 years). Male case-patients reported more activity in wooded and tall grass areas than did female case-patients; fewer male case-patients reported sharing living space with outdoor-exposed companion animals. As age increased, more case-patients reported activity in blacklegged tick habitats, exposure to ticks, and wearing adequate clothing, but fewer reported sharing living space with outdoor-exposed companion animals. Adoption of preventive behaviors was relatively low and did not differ by sex. Male case-patients, children 5-9 years of age and their parents or caregivers, and adults >59 years of age represent populations that would benefit from tailored public health messaging on Lyme disease prevention.

The effect of bubbling on the germination of Sudan grass seeds

In the article the results of experiments to study the effect of bubbling on the germination of Sudan grass seeds before and after cryopreservation were presented. The obtained statistical data were processed using the R-studio program. We calculated the indicators of humidity and germination energy of Sudan grass seeds, and determined the statistically reliable significance between the control and experimental varieties. To conduct the experiment, a bubbler installation was created from a cylindrical container filled with water and a bubbler to supply oxygen. The results of pre-sowing seed treatment were obtained for 4 varieties of Sudan grass: Nika, Tugai, Alina, Novosibirskaya 84. Bubbling increases seed germination compared to the control by 13 % for the Nika variety, by 7 % for the Novosibirskaya 84 variety. While bubbling after cryopreservation significantly reduces the germination of seeds in the Tugai variety by 25 %, in the Alina variety by 32 %, in the Novosibirskaya 84 variety by 33 %, and in the Nika variety by 7 %. Thus, bubbling, in general, had a positive effect on the germination of Sudan grass seeds and may be one of the methods of pre-sowing seed treatment. As a recommendation for improving the germination of Sudan grass seeds, we suggest using bubbling without cryopreservation.

Risk factors for Lyme disease among residents of rural, suburban, and urban areas in the United States: A Case-Control Study

Abstract lyme disease (LD) is the most common vector-borne disease in the United States, with 476,000 cases estimated each year. It is unclear how LD risk factors vary by residential setting. We conducted a case-control study on LD risk by rural, urban, and suburban residential settings. Individuals from 15 high-incidence states and the District of Columbia in the Optum Research Database were identified as cases (LD medical claim) or controls (no LD medical claim, matched by county of residence and census block group population density). Participants were surveyed about LD history, outdoor activities, and residential characteristics. The final analytic dataset had 750 LD cases and 965 controls. Residence in a rural setting had increased LD risk (OR 1.41, 95% CI 1.16, 1.72). In multivariable analyses, activities associated with LD were hiking/walking/running or having an occupation in forests, wooded areas, or areas of tall grass (all respondents), and spending time in a yard (rural and urban residents only). Public health interventions can help prevent LD in high-incidence jurisdictions by reinforcing the nearuniversal LD risk for rural residents, and highlighting activities that lead to increased LD risk for those in areas with less ubiquitous tick exposure like in urban and suburban settings.

Genome sequence of the sugarcane aphid, Melanaphis sacchari (Hemiptera: Aphididae).

The sugarcane aphid, Melanaphis sacchari (Zehntner, 1897), is an agricultural pest that causes damage to plants in the Poaceae (the grasses) family, such as sorghum and sugarcane. Here, we used Nanopore long reads and Hi-C interaction map to generate a chromosome-level assembly with a total length of 356.1 Mb, of which 85.5% (304.6 Mb) is contained within the three autosomes and the X chromosome. Repetitive sequences accounted for 16.29% of the chromosomes and a total of 12,530 protein-coding genes were annotated, achieving 95.8% benchmarking universal single-copy orthologs (BUSCO) gene completeness. This offers a substantial improvement compared to previous low-quality genomic resources. Phylogenomic analysis by comparing M. sacchari with twenty-four published aphid genomes representing three aphid tribes reveals that M. sacchari belongs to the tribe Aphidini and maintained a conserved chromosome structure with other Aphidini species. The high-quality genomic resources reported in this study will be useful for understanding the evolution of aphid genomes and studying pest management of M. sacchari.

One goodness, many goodnesses, and the Divine Ideas Imitation Theory

Abstract Some theories of goodness are descriptively rich: they have much to say about what makes things good. Neo-Aristotelian accounts, for instance, detail the various features that make a human being, a dog, a bee good relative to facts about those forms of life. Famously, such theories of relative goodness tend to be comparatively poor: they have little or nothing to say about what makes one kind of being better than another kind. Other theories of goodness – those that take there to be absolute goodness – are comparatively rich: they offer grounds for judging some types of things better than others because they have more absolute goodness. Moorean accounts, for example, can tell us that humans and human experiences are superior to bees and blades of grass. But such theories tend to be descriptively poor: they struggle to tell us in virtue of what this is so. In this article we motivate and flesh out a view that splits the difference between accounts of goodness as relative and accounts of goodness as absolute. Such a view holds promise only if the mechanics of this kind of metaphysics of goodness can be worked out. Here we present a view on which the paradigm for absolute goodness is God and the paradigm for each kind of relative goodness is a divine idea.

A system for efficient and sustainable cogeneration of water and electricity: Temperature difference induced by photothermal conversion and evaporative cooling

Solar energy, with its sustainable properties, has garnered considerable attention for its potential to produce green electricity and clean water. This paper proposes a multistage energy transfer co-generation system (MWCNTs-covered thermoelectric module with aerogel and cooler, AC-CTEM) combining power generation and evaporative cooling. On the light-absorbing surface, the hot side of a thermoelectric module is covered with a hydrophobic coating made of PDMS and MWCNT. The cold side transfers heat to the evaporation zone using a heat sink. Aerogel evaporators are cross-linked with chitosan and polyurethane, which reduces the enthalpy of evaporation and facilitates efficient interfacial evaporation to remove heat and return it to refrigeration. Additionally, with the addition of Fresnel lenses and wind energy to the enhancement device, the system achieved an evaporation rate of 3.445 kg m−2 h−1 and an open-circuit voltage of 201.12 mV under 1 kW m−2 solar irradiation. The AC-CTEM system also demonstrated long-term stability and effectiveness in treating various types of non-potable water. Furthermore, we demonstrated the practical utility of the system by successfully cultivating grass seeds and powering electronic equipment. The AC-CTEM system exemplifies a practical energy-saving approach for the development of highly efficient co-generation systems.

Reduced seed viability in exchange for transgenerational plant protection: Does the defensive mutualism concept pass the fitness test?

Epichloë endophytes are vertically transmitted via grass seeds and chemically defend their hosts against herbivory. Endophyte-conferred plant defence via alkaloid biosynthesis may occur independently of costs for host plant growth. However, fitness consequences of endophyte-conferred defence and transgenerational effects on herbivore resistance of progeny plants, are rarely studied. The aim of this study was to test whether severe defoliation in mother plants affects their seed production, seed germination rate, and the endophyte-conferred resistance of progeny plants. In a field study, we tested the effects of defoliation and endophyte symbiosis (Epichloë uncinata) on host plant (Festuca pratensis) performance, loline alkaloid concentrations in leaves and seeds, seed biomass and seed germination rates. In a subsequent greenhouse study, we challenged the progeny of the plants from the field study to aphid herbivory and tested whether defoliation of mother plants affects endophyte-conferred resistance against aphids in progeny plants. Defoliation of the mother plants resulted in a reduction of alkaloid concentrations in leaves and elevated the alkaloid concentrations in seeds when compared with non-defoliated endophyte-symbiotic plants. Viability and germination rate of seeds of defoliated endophyte-symbiotic plants were significantly lower compared to those of non-defoliated endophyte-symbiotic plants and endophyte-free (defoliated and non-defoliated) plants. During six weeks growth, seedlings of defoliated endophyte-symbiotic mother plants had elevated alkaloid concentrations, which negatively correlated with aphid performance. Endophyte-conferred investment in higher alkaloid levels in seeds -elicited by defoliation- provided herbivore protection in progenies during the first weeks of plant establishment. Better protection of seeds via high alkaloid concentrations negatively correlated with seed germination indicating trade-off between protection and viability.

Bamboo’s Role in Climate Change Adaptation and Mitigation: An Analysis of Biomass, Carbon Stock, and Economic Potential in Tanzania

Bamboo, a rapidly growing member of the grass family, thrives across diverse climates worldwide and offers vital ecosystem services essential for human well-being and economic development. Notably, bamboo releases 35% more oxygen than other trees and sequesters an average of 12 tons of carbon dioxide per hectare, highlighting its significant ecological benefits. This study analyses the contribution of bamboo to climate change adaptation and mitigation, focusing on Tanzania as a case study. Specifically, the study aims to determine the amount of biomass and carbon stock of bamboo in Tanzania, and estimate the financial benefits from including bamboo in carbon payment projects like REDD+. Utilizing adapted allometric models and data from the National Forest Resources Monitoring and Assessment (NAFORMA) of 2015, the study reveals that Tanzania possesses 4.04 billion tons of stored bamboo biomass and 1.9 billion tons of stored bamboo carbon, translating to an estimated 7.6 billion US dollars in unutilized conservation profit from carbon trading. The findings indicate that 51.4% of the stored bamboo biomass, carbon, and potential conservation profit are concentrated in the genus Bambusa, with nearly half of these resources located in the southern regions of Lindi and Mtwara. These results underscore the substantial ecological and economic benefits of bamboo ecosystem services, emphasizing the need for stakeholders to formulate strategies for the sustainable production, conservation, and management of bamboo in Tanzania. The study provides a benchmark for developing policies and plans that leverage bamboo's potential in climate change adaptation and mitigation, promoting environmental sustainability and economic growth.

Investigating How Nontariff Measures Impact the Turfgrass Seed Trade

Turfgrass seed, a living organism, is facing more stringent trade regulations compared with nonliving products. We applied multiple empirical approaches to explore the impact of these regulations on trade flows in grass seeds. We constructed a series of novel variables to measure these regulations, such as environment regulation stringency, pre-shipment inspections, market conditions, and product requirements. Our results showed that nontariff trade measures had substantial impacts on the trade of grass seeds. These measures sometimes worked as barriers to trade and at other times worked as catalysts for trade.

Genetic divergence and truncation and simultaneous selection in inbred families (S1) of elephant grass for bioenergetic purposes via mixed models

The State University of North Fluminense Darcy Ribeiro (UENF) has been developing for fifteen years a breeding program that aims at the development of new cultivars of elephant grass due to its high potential and the low availability of cultivars developed by genetic breeding programs that meet the needs of producers in the State of Rio de Janeiro. In this sense, inbred families were also obtained as a way of fixing potential alleles for traits related to production, as the inbreeding process apparently does not strongly affect elephant grass in aspects related to inbreeding depression. This study aimed to estimate genetic diversity, variance components and prediction of genotypic values in 11 (S1) elephant grass families, and perform the truncation and simultaneous selection of traits using the selection index, by mixed models. The experimental design consisted of randomized blocks with 11 (S1) families, three replications, and six plants per plot. For variables dry matter production, percentage of dry matter, plant height, stem diameter, number of tillers and leaf blade width, was performed the estimation of genetic parameters and selection of the best genotypes based selection index using mixed model. The descriptors were subjected to correlation analysis, distance matrices were generated by the Mahalanobis method, and individuals were grouped by the UPGMA method. In the selection via mixed models (REML/BLUP), families 6, 11, 8, 1, 3, 7, and 9 contributed most of the genotypes selected for the evaluated traits, indicating their high potential to generate superior genotype. The selection indices via mixed models indicated that the multiplicative index presented a greater selection gain.The phenotypic correlations showed the possibility of performing an indirect selection from six evaluated traits.The genotypes were separated into 18 groups by the Mahalanobis distance, allowing the observation of a wide genetic diversity. The most divergent and productive genotypes were self-fertilized to obtain the second generation (S2), continuing the development program.

Taxonomic and environmental significance of Poaceae and Cyperaceae phytoliths from the Northern Territory, Australia

Phytoliths are a valuable tool for reconstructing past grassy ecosystems. However, they are not commonly utilised as a palaeoecological proxy in Australia due to a lack of modern reference material from plants, particularly grasses. This study analyses phytolith reference material from 49 grass and 4 sedge species from the Northern Territory, Australia. This is used to develop a detailed classification scheme and multivariate morphospace analysis to examine taxonomic and ecological patterns of grass silica short cell phytolith (GSSCP) production within the Poaceae (grass) family. The results of detrended correspondence analysis show that grass subfamilies, tribes, and genera in this region can be differentiated through phytolith assemblages, and that these assemblages reflect the environmental conditions associated with various grass taxa. The developed detailed classification system and examination of co-occurrence patterns reduces redundancy of phytolith morphotypes across subfamilies, improving taxonomic and palaeoecological resolution of phytolith assemblages. Finally, based on the results of this study, a detailed scheme is presented for palaeoecological reconstructions in grassy ecosystems of northern Australia.

Genomic and Transcriptomic Insights into the Evolution of C4 Photosynthesis in Grasses.

C4 photosynthesis has independently evolved over 62 times within 19 angiosperm families. The recurrent evolution of C4 photosynthesis appears to contradict the complex anatomical and biochemical modifications required for the transition from C3 to C4 photosynthesis. In this study, we conducted an integrated analysis of genomics and transcriptomics to elucidate the molecular underpinnings of convergent C4 evolution in the grass family. Our genome-wide exploration of C4-related gene families suggests that the expansion of these gene families may have played an important role in facilitating C4 evolution in the grass family. A phylogenomic synteny network analysis uncovered the emergence of C4 genes in various C4 grass lineages from a common ancestral gene pool. Moreover, through a comparison between non-C4 and C4 PEPCs, we pinpointed 14 amino acid sites exhibiting parallel adaptations. These adaptations, occurring post the BEP-PACMAD divergence, shed light on why all C4 origins in grasses are confined to the PACMAD clade. Furthermore, our study revealed that the ancestor of Chloridoideae grasses possessed a more favorable molecular preadaptation for C4 functions compared to the ancestor of Panicoideae grasses. This molecular preadaptation potentially explains why C4 photosynthesis evolved earlier in Chloridoideae than in Panicoideae and why the C3-to-C4 transition occurred once in Chloridoideae but multiple times in Panicoideae. Additionally, we found that C4 genes share similar cis-elements across independent C4 lineages. Notably, NAD-ME subtype grasses may have retained the ancestral regulatory machinery of the C4 NADP-ME gene, while NADP-ME subtype grasses might have undergone unique cis-element modifications.

Fungi associated with seeds of the invasive grass Nassella trichotoma (serrated tussock) in its native range as prospective biological control agents

Context The South American grass Nassella trichotoma (serrated tussock) is widely distributed in central Argentina and one of the most damaging invasive species in Australia, New Zealand, and South Africa. In Australia, it is a weed of national significance. Aims Our aim was to characterise the fungi able to colonise N. trichotoma seeds buried at a site in south-western Buenos Aires province, Argentina, and measure their impact on seed survival and germination. Methods We tested the germination of healthy seeds at the beginning of the experiment (control). We buried 10 mesh bags containing 100 disinfected N. trichotoma seeds each, during 3 months in spring and autumn. At the end of each experiment, the contents of five of the bags were counted and classified as germinated, healthy, damaged, or disintegrated. Germination tests were then conducted with seeds of the latter three categories. The remaining seeds were used for recording fungal signs/symptoms, and the isolation of fungi. Key results We identified and described a diverse group of fungi associated with the seeds and a seasonal variation in the specific composition. Seeds showing fungal signs and/or symptoms germinated less than the control. Conclusions This is the first study on fungi associated with seeds of this species in the native range, which can affect their survival and longevity. Implications It is expected that studies on the seed microbiome may help us understand the differences in behaviour of the plant between ranges, and test the enemy-release hypothesis.

Prevalence and Diversity of Aphid-Vectored Yellow Dwarf Viruses in Oregon Perennial Grass Seed Crops

Oregon produces 70% of the world's cool-season grass seed, many species of which are susceptible to yellow dwarf viruses (YDVs). This virus complex has numerous defined virus species vectored by multiple aphid species. The diversity of YDVs associated with Oregon grass seed production has not been determined and is needed to provide insight to develop a risk prediction framework and improve management guidelines to mitigate disease severity. Commercial grass seed fields ( n = 57) across the Willamette Valley and central and eastern Oregon were surveyed across 2021 and 2022 to determine the incidence and diversity of YDVs associated with crop species (perennial ryegrass, tall fescue, and Kentucky bluegrass) and the abundance and incidence of YDVs associated with aphid vectors. Virus incidence and diversity were determined using multiple previously published endpoint reverse-transcriptase multiplexes specific for YDV genera and species. Across commercial grass seed crop hosts and growing seasons, 82% of fields had at least one plant sample detection of a luteovirus-type YDV, and 65% had at least one detection of a polerovirus-type YDV. Both perennial ryegrass and tall fescue crops hosted diverse YDV populations, which was especially apparent during the spring sampling season, when similarly diverse YDV communities were found associated with alate aphids. Only polerovirus-type YDVs were detected in Kentucky bluegrass, reflecting a variable landscape compared to Oregon's western Willamette Valley. This study provides a current understanding of the spatial composition and diversity of the aphid–YDV virus–vector system in grasses grown for seed in Oregon. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2024.

Niche separation of three species of tree-rat (black-footed tree-rat, M. gouldii, golden-backed tree-rat, Mesembriomys macrurus, and brush-tailed rabbit-rat, Conilurus penicillatus) on the Mitchell Plateau, Western Australia

Context Distribution and abundance of the three northern Australian tree-rat species, Conilurus penicillatus, Mesembriomys macrurus and M. gouldii, have contracted significantly since European settlement. All three species were recorded from the Mitchell Plateau, Western Australia, in the 1980s, enabling their niche separation to be assessed. Despite this study being conducted in 1987, the results remain relevant for conservation strategies for these species. Aims To determine the ecological separation among three tropical tree-rat species by documenting habitat preferences, habitat use and diet. Methods Live-trapping, radiotracking and spotlighting were used to assess relative abundance, habitat preference and movements of each species at nine sites on the Mitchell Plateau. Diet was determined using scat analysis; vegetation communities were described and characterised by pattern analysis. Key results C. penicillatus (number of individuals trapped (n) = 24) was most abundant, followed by M. macrurus (n = 8) and M. gouldii (n = 2). Mature open forest with a well-developed understorey was preferred by the predominantly arboreal M. gouldii (1 site), M. macrurus occupied more varied habitats (four sites), especially ecotones between vine thicket and open eucalypt forest and the boulder edges of the plateau, and C. penicillatus occupied the greatest variety of habitats (four sites) in open eucalypt woodland with a diverse shrub layer and ground cover almost absent to very dense, tall grass. Diet analysis identified M. gouldii as a frugivore (fruits, some flowers), M. macrurus as an omnivore (seeds, fruits, flowers, termites, other invertebrates), and C. penicillatus as a generalist (monocot and dicot leaves, seeds, flowers, fruits, some arthropods). Conclusions The largest of the species, M. gouldii, appeared to have the narrowest ecological niche, preferring more stable, structurally diverse, mature open forest that is infrequently burnt. The mid-sized M. macrurus occupies a broader range of habitats, particularly ecotones between vine thickets and eucalypt forest/woodland and woodland. C. penicillatus preferred open eucalypt woodland with a variable understorey. Implications With a changing climate, increased fire frequency, habitat degradation by introduced herbivores and predation by cats across the tropical savanna distribution of these threatened tree-rats, this study provides data to underpin actions that may ensure their survival.

Parameter Design and Optimization of Grass Aerial Seeding Tower Based Computational Fluid Dynamics

Unstable airflow driven by natural wind forces inside a grass aerial seeding tower is a technical problem that needs to be improved. The authors used FLUENT 2020 R2 to simulate a basic nozzle unit, which is the fundamental component of a grass aerial seeding tower. The interior flow characteristics of the tower were first analyzed. Then, an optimization was undertaken to enhance the internal airflow’s uniform stability, taking the cross-sectional inclination angle as the design parameter. The coefficient of variation, uniformity index, and velocity direction index were considered as constraints. The simulation results indicate that, subsequent to traversing the Laval nozzle unit, the grass seeds undergo a considerable acceleration. At an inclination angle of 15°, while ensuring the attainment of desired exit velocities, a commendable balance of uniformity and directional consistency was achieved.