Photosynthetic Area Research Articles

Geo-Based Assessment of Vegetation Health Related to Agroecological Practices in the Southeast of Togo

In the context of climate change, the need to contribute to achieving Sustainable Development Goal (SDG) 2 is no longer in doubt, especially in sub-Saharan Africa. In this study of the landscape within 10 km of the Donomadé model farm, southeastern Togo, researchers sought to assess vegetation health in ecosystems and agrosystems, including their capacity to produce biomass for agroecological practices. Sentinel-2 sensor data from 2015, 2017, 2020, and 2022 were preprocessed and used to calculate the normalized vegetation fire ratio index (NBR), the vegetation fire severity index (dNBR), and CASA-SEBAL models. From these different analyses, it was found that vegetation stress increased across the landscape depending on the year of the time series. The research estimated that 9952.215 ha, 10,397.43 ha, and 9854.90 ha were highly stressed in 2015, 2017, and 2020, respectively. Analysis of the level of interannual severity revealed the existence of highly photosynthetic areas that had experienced stress. These areas, which were likely to have been subjected to agricultural practices, were estimated to be 8704.871 ha (dNBR2017–2015), 8253.17 ha (dNBR2020–2017), and 7513.93 ha (dNBR2022–2020). In 2022, the total available biomass estimated by remote sensing was 3,741,715 ± 119.26 kgC/ha/y. The annual average was 3401.55 ± 119.26 kgC/ha/y. In contrast, the total area of healthy vegetation was estimated to be 4594.43 ha, 4301.30 ha, and 4320.85 ha, in 2015, 2017, and 2022, respectively. The acceptance threshold of the net primary productivity (NPP) of the study area was 96%. The coefficient of skewness (0.81 ± 0.073) indicated a mosaic landscape. Productive and functional ecosystem components were present, but these were highly dispersed. These findings suggest a great opportunity to promote agroecological practices. Mulching may be an excellent technique for enhancing overall ecosystem services as targeted by the SDGs, by means of reconversion of plant biomass consumed by vegetation fires or slash-and-burn agricultural practices.

Effect of different levels of EDTA on phytoextraction of heavy metal and growth of Brassica juncea L.

Heavy metal pollution of soil is a major concern due to its non-biodegradable nature, bioaccumulation, and persistence in the environment. To explore the probable function of EDTA in ameliorating heavy metal toxicity and achieve the sustainable development goal (SDG), Brassica juncea L. seedlings were treated with different concentrations of EDTA (0, 1.0, 2.0, 3.0, and 4.0 mM Kg-1) in heavy metal-polluted soil. Plant samples were collected 60 days after sowing; photosynthetic pigments, H2O2, monoaldehyde (MDA), antioxidant enzymes, and ascorbic acid content, as well as plant biomass, were estimated in plants. Soil and plant samples were also examined for the concentrations of Cd, Cr, Pb, and Hg. Moreover, values of the phytoremediation factor were utilized to assess the accumulation capacity of heavy metals by B. juncea under EDTA treatments. In the absence of EDTA, B. juncea seedlings accrued heavy metals in their roots and shoots in a concentration-dependent manner. However, the highest biomass of plants (roots and shoots) was recorded with the application of 2 mM kg-1 EDTA. Moreover, high levels (above 3 mM kg-1) of EDTA concentration have reduced the biomass of plants (roots and shoots), photosynthetic area, and chlorophyll content. The effect of EDTA levels on photosynthetic pigments (chlorophyll a and b) revealed that with an increment in EDTA concentration, accumulation of heavy metals was also increased in the plant, subsequently decreasing the chlorophyll a and b concentration in the plant. TLF was found to be in the order Pb> Hg> Zn> and >Ni, while TF was found to be in the order Hg>Zn>Ni>Pb, and the best dose was 3 mM kg-1 EDTA for Hg and 4 mM kg-1 for Pb, Ni, and Zn. Furthermore, hyperaccumulation of heavy metals enhanced the generation of hydrogen peroxide (H2O2), superoxide anions (O2•-), and lipid peroxidation. It also interrupts mechanisms of the antioxidant defense system. Furthermore, heavy metal stress reduced plant growth, biomass, and chlorophyll (chl) content. These findings suggest that the exogenous addition of EDTA to the heavy metal-treated seedlings increases the bioavailability of heavy metals for phytoextraction and decreases heavy metal-induced oxidative injuries by restricting heavy metal uptake and components of their antioxidant defense systems.

First report of Neopestalotiopsis foedans causing pestalotia spot in leaf on coconut in Brazil.

The coconut (Cocos nucifera L., Arecaceae) is one of the most important tropical species used by humans. In Brazil, its cultivation has been expanding in the recent years (Souza et al. 2020) and many diseases have emerged. The pestalotia spot, caused by Pestalotiopsis guepinii (Desm.), is a leaf disease of the coconut characterized by elliptic lesions with defined dark borders varying in size from 3 to 5 mm (Cardoso et al. 2003). In January of 2018, leaves with symptoms of pestalotia spot were obtained from ten year old coconut plants "dwarf variety" in a commercial planting in the city of Neópolis (10°20'S/36°42'W), Sergipe, Brazil. Disease incidence was 80% on 60 plants observed. Twenty samples of symptomatic tissues were collected and disinfested for 2 min in 1% sodium hypochlorite, washed in sterile water, placed on PDA (potato dextrose agar), and incubated at 25 ± 1°C with a 12-h photoperiod for 4 days. Five isolates were obtained, and pure cultures deposited in Phytopathogen Collection of the Federal University of Alagoas, accession numbers: COUFAL0240 to COUFAL0244. Seven day old colonies grown on PDA at 25°C, were whitish with aerial mycelium on the surface and abundant production of black conidiomata. Conidia were fusiform, straight to slightly curved with five cells, three median cells with brown coloring being the second and third being darker and the apical and basal cells, hyaline. Fifty conidia were measured and varied in size from 20.02-24.26 x 5.37-7.50 μm. The conidia presented two to four apical appendages and one basal appendage (Fig. S1). The morphological characteristics coincide with the Neopestalotiopsis foedans (Sacc. & Ellis), Maharachchikumbura et al. (2014). Molecular identification was conducted using partial nucleotide sequences from the ITS (ITS1/ITS4) region (GenBank no. MT605375 to MT605379) and from the genes TUB2 (Bt2a/Bt2B) (no. MT634202 to MT634206) and TEF-1α (526F/1567R) (no. MT634197 to MT634201). Besides that, the isolates grouped with the ex-type N. foedans species (CGMCC 3.9123) in a phylogenetic tree of Bayesian inference using concatenated sequences (Fig. S2). The pathogenicity was confirmed on seedling from coconut plants "dwarf variety" maintained in a greenhouse. Four plants were used, being one as a control. Spore suspensions of 106 conidia mL-1 was prepared from a 7 days old culture (cultivated at 25ºC). Inoculations were performed by spraying the conidial suspension on two whole leaves per plant (wounded and unwounded). In the control, sterilized distilled water was used. Plants were incubated at 25 ± 1°C and 100% relative humidity. Ten days after inoculation, depressed and necrotic lesions were observed in 100% on the inoculated leaves with wound. No symptoms observed on unwounded leaves, nor in the control treatment. To complete Koch's postulates, the N. foedans fungus was successfully re-isolated from the symptomatic leaves and identified phenotypically in optical microscope. Neopestalotiopsis foedans has already been reported in Calliandra haematocephala (Hassk), Neodypsis decaryi (Jum.), Rhizophora mangle (L.), Thuja occidentalis and Psidium guajava (L.) (Saccardo, 1882; Maharachchikumbura et al. 2014, Solarte et al. 2018). However, this is first report of N. foedans causing leaf spot in coconut in the world. The pestalotia spot is commonly observed in Brazil in C. nucifera and should be considered an important disease for this culture, as this can significantly reduce its photosynthetic area.

Uncovering the potentials of long-term straw return and nitrogen supply on subtropical maize (Zea mays L.) photosynthesis and grain yield

ContextCrop straw is a significant byproduct of agricultural production and a rich source of nutrients, but it is carelessly disposed of, potentially harming the environment and wasting valuable resources. In China, returning straw to the soil as a means of disposing of agricultural waste is a crucial management technique that not only makes use of agricultural waste but also enhances soil quality and grain yield. ObjectiveA five-year (2018–2022) field experiment was designed to study the effect of straw treatment methods and optimal nitrogen (N) application rate on the photosynthesis process and grain yield of maize. MethodsThe different straw methods (straw return (SR) and traditional practice (TP) — no straw return) were assigned to main plots while the N levels such as N100 (100 kg ha−1), N150 (150 kg ha−1), N200 (200 kg ha−1), N250 (250 kg ha−1), and N300 (300 kg ha−1) were allotted to sub-plots. ResultsThe results showed the photosynthesis rate (Pn), intercellular carbon dioxide concentration, stomatal conductance, transpiration rate, relative chlorophyll content (SPAD), leaf area index (LAI), dry matter (DM), soil nitrogen content, maize grain nitrogen accumulation, and grain yield were increased with an increase in N levels. Similarly, SR also showed a promotion effect on the aforementioned parameters compared with TP. After five years, SR with an optimum N level (250 kg ha−1) increased the SPAD values (2%) and Pn (8%) which resulted in higher LAI (27%) compared with TPN300. As a result, more DM (15%) was formed and finally increased the grain yield (7%). It was revealed that the SPAD, Pn, LAI, DM, and grain yield were maximum at a higher 300 kg N ha−1 level but it was found statistically similar with 250 kg N ha−1. So in this study, SR with 250 kg N ha−1 is optimum for better photosynthetic efficiency, dry matter production, and grain yield. The correlation analysis also showed a positive correlation (i) of SPAD values with Pn (ii) LAI with SPAD values and Pn, (iii) DM with SPAD values, Pn, and LAI, and (iv) grain yield with DM under SR compared with TP. Conclusion and implicationIn summary, SRN250 resulted in better chlorophyll content and photosynthesis process that yielded more photosynthetic area for higher DM production and subsequently higher maize grain yield. The SR reduced the amount of N fertilizer and improved the grain yield and it is the best approach to improve grain yield and minimize agricultural waste production. Long-term trials are needed to understand the effects of straw incorporation and nitrogen application in different regions and locations.

Entomopathogenic fungi associated with cultivated honeybush, Cyclopia spp., in South Africa and their pathogenicity towards a leafhopper pest, Molopopterus sp. (Hemiptera: Cicadellidae)

The southern and eastern parts of the African Fynbos region favour the production of honeybush tea. Honeybush biomass and extracts are used to prepare a beverage both locally and internationally, mainly as herbal tea with health benefits. Honeybush tea is mostly grown organically requiring natural control measures for pests and diseases. The leafhopper, Molopopterus sp., is one of the most important pests of cultivated honeybush in South Africa, as its feeding compromises the quality and quantity of the yield through leaf discolouration and reduction of the photosynthetic area. Local entomopathogenic fungi (EPF) can provide a pool of potential biocontrol agents for this pest. Therefore, a total of 98 soil samples were collected from organically grown honeybush fields and vegetation surrounding the honeybush fields in the Western Cape province of South Africa. Entomopathogenic fungi were isolated using the insect bait method and were characterised using molecular techniques. Twenty fungal isolates of Metarhizium anisopliae and Fusarium oxysporum were recovered from soil samples, of which 70% were from honeybush fields and 30% were from surrounding vegetation. Fusarium oxysporum isolates comprised 20% of the recovered isolates; M. anisopliae the remainder. Laboratory bioassays of the recovered isolates against adults and nymphs of the leafhopper, showed that F. oxysporum isolates caused 10–45% mortality and M. anisopliae isolates 30–80% mortality. Metarhizium anisopliae isolates J S1, KF S3, KF S11, KF S13, LS1 and LS2 were the most virulent and induced over 60% mortality in both nymphs and adults at a concentration of 1 × 107 conidia/ml.

Simultaneous Application of Red and Blue Light Regulate Carbon and Nitrogen Metabolism, Induces Antioxidant Defense System and Promote Growth in Rice Seedlings under Low Light Stress.

The purpose of this study is to determine the effect of light quality on growth, carbon and nitrogen metabolism, and antioxidant defense system of rice seedlings. Six light conditions were employed, including white (W), red (R), blue (B), combined LED of R and B at 3:1 (R3B1), combined LED of R and B at 1:1 (R1B1), as well as combined LED of R and B at 1:3 (R1B3). Combined application of red light and blue light could promote the growth of rice seedling leaves and roots under low light stress to varying degrees, increase the photosynthetic area by increasing the leaf area, improve the root characteristics by increasing the root volume, and increase the dry matter accumulation of rice seedlings. In addition, the combination of red light and blue light could increase carbon and nitrogen metabolites in rice seedling leaves, regulate the expression of genes related to carbon and nitrogen metabolism and enzyme activity, and enhance the antioxidant enzyme activity of rice seedlings. These results indicate that red light and blue light directly have synergistic effects which can regulate the carbon and nitrogen metabolism of rice seedlings, promote the morphogenesis of rice seedlings under low light stress, and promote growth, which has never been reported in previous studies. This study is a new discovery in the application of light quality in crop production and provides new avenues to enhance crop stress resistance. However, further study is needed to explore the physio-biochemical and molecular mechanisms of light quality in crop production.

Potential Biocontrol Agents of Corn Tar Spot Disease Isolated from Overwintered Phyllachora maydis Stromata.

Tar spot disease in corn, caused by Phyllachora maydis, can reduce grain yield by limiting the total photosynthetic area in leaves. Stromata of P. maydis are long-term survival structures that can germinate and release spores in a gelatinous matrix in the spring, which are thought to serve as inoculum in newly planted fields. In this study, overwintered stromata in corn leaves were collected in Central Illinois, surface sterilized, and caged on water agar medium. Fungi and bacteria were collected from the surface of stromata that did not germinate and showed microbial growth. Twenty-two Alternaria isolates and three Cladosporium isolates were collected. Eighteen bacteria, most frequently Pseudomonas and Pantoea species, were also isolated. Spores of Alternaria, Cladosporium, and Gliocladium catenulatum (formulated as a commercial biofungicide) reduced the number of stromata that germinated compared to control untreated stromata. These data suggest that fungi collected from overwintered tar spot stromata can serve as biological control organisms against tar spot disease.

Prevalence and Severity of Sigatoka Disease of Banana in Cameroon

Sigatoka Disease (SD) represents the major pre-harvest fungal disease of banana and also appear as the major constraint of banana production. This diseaseis caused by two major pathogenic fungi, Pseudocercospora fijiensis and P. musicola. It provokes necrotic lesions on leaves and serious infestations leads to a substantial reduction in the green leaf area of infected plants and thus the photosynthetic area of the plant and consequently leads to yield loss. In the present work, three plantations were surveyed and experiments conducted in Southwest Cameroon to assess the prevalence and severity of sigatoaka disease in the banana plantations. Our results revealed a 100 % prevalence of Sigatoka in the field with an incidence of 59 %. In a severe manner, the severity in all the plantations was seen to have a constant increase with the highest severity at 23.83 % observed in plantation 1. In a nutshell, the incidence and severity of the disease was seen to increase with respect to time and season.

Evaluating the Losses and Recovery of GPP in the Subtropical Mangrove Forest Directly Attacked by Tropical Cyclone: Case Study in Hainan Island

The gross primary production (GPP) of the mangrove ecosystem determines the upper limit of the scale of its “blue carbon” sink. Tropical cyclones (TCs) are among the most important extreme events that threaten the subtropical mangrove ecosystem and have a serious impact on mangrove ecosystem GPP. However, there are somewhat insufficient scientific findings on regional-scale mangrove ecosystem GPP responding to large-scale weather events such as TCs. Therefore, we selected the subtropical Hainan Island mangrove ecosystem, where more than two TCs pass through per year, as the research area; selected direct-attack TCs as the research object; and took the mangrove vegetation photosynthesis light-use efficiency model established based on the eddy covariance observation data as the tool to evaluate the loss and recovery of mangrove ecosystem GPP after TCs attacked at a regional scale. We found that the TC impacted the mangrove ecosystem GPP through the photosynthetic area and rate, and the recovery of the rate occurred prior to the recovery of the area; the loss of mangrove ecosystem GPP is inversely proportional to the distance to the center of the TC and the distance to the coastline; and the canopy height, diameter at breast height, and aspect where the tree stands significantly influence the response of the mangrove ecosystem GPP to TCs. However, the response varies for different mangrove community compositions, soil conditions, and planting densities as well as different frequencies and intensities of TCs, and they should be analyzed in detail. This study is expected to provide technical and data support for the protection of blue carbon in a subtropical island mangrove ecosystem in response to extreme events and post-disaster recovery.

Identification of a Rice Leaf Width Gene Narrow Leaf 22 (NAL22) through Genome-Wide Association Study and Gene Editing Technology.

Rice leaf width (RLW) is a crucial determinant of photosynthetic area. Despite the discovery of several genes controlling RLW, the underlying genetic architecture remains unclear. In order to better understand RLW, this study conducted a genome-wide association study (GWAS) on 351 accessions from the rice diversity population II (RDP-II). The results revealed 12 loci associated with leaf width (LALW). In LALW4, we identified one gene, Narrow Leaf 22 (NAL22), whose polymorphisms and expression levels were associated with RLW variation. Knocking out this gene in Zhonghua11, using CRISPR/Cas9 gene editing technology, resulted in a short and narrow leaf phenotype. However, seed width remained unchanged. Additionally, we discovered that the vein width and expression levels of genes associated with cell division were suppressed in nal22 mutants. Gibberellin (GA) was also found to negatively regulate NAL22 expression and impact RLW. In summary, we dissected the genetic architecture of RLW and identified a gene, NAL22, which provides new loci for further RLW studies and a target gene for leaf shape design in modern rice breeding.

Photosynthetic capacity of Erigeron canadensis L. may be more critical to its growth performance than photosynthetic area

Photosynthetic capacity of Erigeron canadensis L. may be more critical to its growth performance than photosynthetic area

Stemphylium vesicarium (wallr.) E.G. Simmons: An onion plant pathogen and options for suppression

Onion (Allium cepa L.) is one of the most important vegetable species grown worldwide, including the Republic of Serbia. Leaf blight, caused by the fungus Stemphylium vesicarium, is a serious and destructive disease of onion leaves around the world, which limits the quality and quantity of bulbs and seeds. Yield decrease occurs due to a reduced photosynthetic area, which leads to the formation of smaller bulbs of poorer quality. The recommended strategy for control and reduction of SLB inoculum includes crop rotation with other vegetable species or cereals that are not hosts of these fungi, the use of resistant onion genotypes, weed removal, adequate use of nitrogen fertilizers, control of thrips (Thrips spp.), as well as seed treatment, considering that seeds play a significant role in the spread of pathogens. Timely and correct application of foliar fungicides is certainly the key strategy. The timing of application of fungicides with different modes of action is crucial for controlling Stemphylium vesicarium in onion.

High plant density increases sunlight interception and yield of direct-seeded winter canola in China

Summary Rationally higher population density is crucial for seeking a balance that meets lodging resistance and maximizes seed yield in mechanized direct-seeded winter canola. In this study, a split-plot experiment with two cultivars (Huayouza9 and Zhongshuang11) and eleven planting densities (12–105 plants m-2) was conducted in a two-season field experiment to evaluate the high planting density in this cropping system and improve its production efficiency. Seed yield noticeably increased in planting density up to 80 plants m-2 in Zhongshuang11 (2187 kg hm-2) and 60 plants m-2 in Huayouza9 (2943 kg hm-2). The seed yield of Huayouza9 did not differ significantly from the local target seed yield. Higher plant density curtailed the luxurious vegetative growth of individual canola plants at the density of no less than 60–80 plants m-2, and high seed yield was derived from the increased ratio of main raceme and branch seed weight in winter canola. An increase in plant densities contributed to the reinforced sunlight interception at the pod-filling stage, providing a larger canopy photosynthetic area for the rapid growth of more canola pods at higher densities (60–105 plants m-2). Lodging resistance and breaking resistance decreased sharply with the plant density increasing from 12 to 60 plants m-2 while remaining almost steady as it further increased from 60 to 105 plants m-2 for Huayouza9 and Zhongshuang11. Hence, the population density of 60 plants m-2 reached a balance between lodging resistance and maximized seed yield in mechanized direct-seeded winter canola in China.

Phenotypic and Molecular Identification of Green Pea Powdery Mildew Pathogen from Alborz, Iran

Green pea (Pisum sativum.) is an important consumable vegetable crop worldwide rich in protein, vitamins, and nutrition. It is cultivated in many parts of Iran, particularly during the summer season, and recently under protected greenhouse. Powdery mildew is an important disease of green pea, especially during the pod fill and maturation stage and decreases the photosynthetic area of leaves which causes crop loss. This experiment was conducted in order to identify fungi associated with powdery mildews on some accessions under regeneration of green pea collection at the genetic department and national plant gene bank of Iran, seed, and plant improvement institute during the year 2021. Powdery mildew became epidemic on the plants at the pod stage from the end of July to August. The formation of white, floury patches initially on the leaf progressing towards tendrils, pods, and stems observed that on susceptible accessions covered the most aerial part of the plants. The Erysiphe pisi, Erysiphe trifolii and Erysiphe baeumleri were reported causing disease on pea. The infected plant samples were collected and transferred to the lab for morphological studies, then, the genomic DNA was isolated and used for amplification and sequencing using the internal transcribed spacers (ITS) regions. Based on morphological characteristics of asexual and sexual stages as well as rDNA-ITS sequence analyses, the fungus was identified as Erysiphe pisi. Due to the presence of accessions with high levels of resistance to this disease, further investigation is recommended to breed resistant cultivars for cultivation in this province.

Evaluation of two artificial defoliation methods to simulate damage by the cereal leaf beetle (Oulema melanopus) larvae in winter wheat

AbstractDefoliation reduces photosynthetic area, negatively effecting overall plant vitality, which at the end, severely impacts seed quality and production. The economic importance of the loss in winter wheat (Triticum aestivum L.) due to larvae of the cereal leaf beetle (Oulema melanopus, CLB) generated studies investigating the significance of the flag leaf. Simultaneously, the role of other leaves remains rather undiscovered. We simulated herbivory caused by CLB larvae in a two-year study between 2017 and 2018. We removed different amounts of leaf material from two winter wheat cultivars, either from the flag leaves only, or from all leaves. The impact of artificial defoliation was measured in grain production per ear, and related to natural CLB larval herbivory. Removing all leaves simulated CLB larval herbivory more closely than the artificial defoliation of flag leaves only. Our results suggest that the relative importance of flag leaves in seed production may be lower than previously assumed. Further studies involving various cultivars are invited to enhance the knowledge on the significance of the damage done by CLB larvae.

BIO-MANAGEMENT OF FUNGAL LEAF SPOT OF TOMATO (SOLANUM LYCOPERSICUM L.) USING INDIGENOUS TRICHODERMA ISOLATES

One of the main obstacles to feeding the world is the fungal leaf spot disease, which has a negative impact on plants' photosynthetic areas and significantly lowers crop quality and output. To manage fungi that pose a serious hazard to both humans and the environment, various chemical fungicides are utilized. The goal of the current study was to determine whether local isolates of three Trichoderma spp. (Trichoderma viride, Trichoderma harzianum, and Trichoderma asperellum) had any antagonistic effects in vitro against the pathogenic fungi Alternaria alternata, Fusarium solani, Fusarium oxysporum, Aspergillus flavus, Aspergillus sydowii, and Alternaria sp. Trichoderma viride showed the greatest growth inhibition against all of the tested pathogenic fungi, followed by Trichoderma harzianum and Trichoderma asperellum. It was shown that all three Trichoderma species strongly inhibited the mycelial growth of fungal pathogens. Compared to other isolated fungi, Trichoderma species inhibited Alternaria alternata mycelial growth more, whereas in Fusarium oxysporum least amount of mycelial growth inhibition was observed. These findings imply that Trichoderma species can function as an effective biocontrol agent against the fungi responsible for tomato leaf spot disease.

Rhus typhina L. triggered greater allelopathic effects than Koelreuteria paniculata Laxm under ammonium fertilization

Most of the allelopathic studies have concentrated on the allelopathic effects of invasive herbaceous plants on the natives, particularly on seed germination and seedling growth (Sge&Sgr), but have ignored the allelopathic effects of invasive trees and the differences in the allelopathic effects of invasive plants (particularly invasive trees) and the natives. Nevertheless, the variations in the ratio of different nitrogen (N) forms in N fertilization can change the differences in the allelopathic effects of the invasive plants and the natives. Thus, it is important to evaluate the differences in the allelopathic effects of invasive plants (particularly invasive trees) and the natives under N fertilization, particularly with different N forms. However, the recent process in this area is limited. This study aimed to estimate the differences in the allelopathic effects (using aqueous leaf extracts) of one of the most destructive invasive trees in China (Rhus typhina L.) and the native tree (Koelreuteria paniculata Laxm) on Sge&Sgr of the horticultural species Lactuca sativa L. under N fertilization with different forms (i.e., N-NH4, N-NO3, urea, and a mixture of the three N forms at a 1:1:1 ratio). The two deciduous Sapindales trees generated significantly allelopathic effects on Sge&Sgr of L. sativa. R. typhina created stronger allelopathic effects on leaf photosynthetic area, plant growth competitiveness, and plant water content of L. sativa than K. paniculate. N solution can intensify the allelopathic effects of the two deciduous Sapindales trees on seedling growth of L. sativa. The allelopathic effects of R. typhina on seedling growth of L. sativa were significantly greater than those of K. paniculata under N-NH4. Thus, the growth competitiveness of R. typhina may be higher than that of K. paniculata under N-NH4 via the stronger allelopathic effects on adjacent species.

Early leaf development of Typha domingensis Pers. (Typhaceae)

ABSTRACT Typha domingensis Pers. (cattail) is a globally widespread aquatic plant that causes significant impacts as an invasive species; this ability is dependent on its photosynthetic capacity that is related to leaves. Thus, understanding leaf development is essential for interpreting shoot growth and the formation of its photosynthetic area. This study investigates leaf ontogeny in T. domingensis from early stages until complete development of primary tissues. Plants were collected from natural wetlands and cultivated in a greenhouse. Rhizomes were then selected, and leaves were removed to enable the emergence of new shoots. Rhizome fragments containing leaves were collected at 1-day intervals until day 7 and were subjected to routine procedures in plant microtechnique. New leaves emerged from lateral buds located along the rhizome. The anatomy of scale leaves differs from that of photosynthetic leaves since they contain solid inclusions without palisade parenchyma. Leaf primordia arose laterally from the shoot apical meristem, which was organized as a tunica-corpus. Final leaf shape was influenced by different meristematic zones: the leaf apical meristem, the marginal meristem, the rib meristem, and intercalary meristems. Most leaf tissues developed basipetally, except for xylem and phloem. Within seven days following leaf initiation, all primary tissues were developed and morphologically functional. Leaf formation of Typha domingensis is similar to that of other monocot species. Leaves of T. domingensis develop very early, providing fully functional photosynthetic tissues, which may have implications for its invasive capacity.

Bio-efficacy of new fungicide, Tebuconazole- 430SC against coffee leaf rust disease, Hemileia vastatrix Berk and Broome

Coffee is an important plantation crop cultivated worldwide and used as stimulating drink. Coffee leaf rust (CLR) disease is one of the devastating disease affecting foliage of Coffee, limiting Coffee production worldwide. It is caused by an obligate parasite Hemileia vastatrix, which reduce photosynthetic area in turn results in heavy defoliation and die-back of branches. In India CLR management is accomplished with one contact fungicide spray (Bordeaux mixture @ 0.5%) and effective systemic fungicide spray during pre and post monsoon periods respectively. However, to find an alternative to the recommended fungicide the studies were conducted to know the efficacy of new fungicide Tebuconazole 430 SC against CLR. The results revealed that, in the laboratory conditions, complete inhibition of the uredospore germination was observed in Tebuconazole 430 SC @ 0.5 ml/L and 0.75 ml/L and Hexaconazole 5 EC @ 2 ml/L. However, in lower concentration Tebuconazole 430 SC @0.25 ml/L there was 98.97 per cent inhibition and in Copper Oxychloride 50 WP @ 5.5 g/L 87.49 per cent inhibition was observed over control. Field trials indicated that, at all the locations, Tebuconazole 430SC @ 0.75ml/L was found very effective which recorded maximum disease reduction followed by Tebuconazole 430SC @ 0.5ml/L which was found on-par with the currently recommended fungicide Hexaconazole 5 EC @ 2 ml/L and minimum disease reduction was observed in Copper oxychloride 50 WP @ 5.5g/L.

Less Than the Sum of Its Parts: Blade Clustering Reduces Drag in the Bull Kelp, Nereocystis luetkeana (Phaeophyceae).

Nereocystis luetkeana is a large, canopy-forming kelp that is commonly found in nearshore waters between Alaska and California. Despite regularly reaching lengths in excess of 30 m, this alga demonstrates a remarkable ability to endure hydrodynamically stressful environments without being dislodged by waves or currents. While morphological aspects of this kelp, including its long flexible stipe, have been shown to reduce drag, blade clustering has never been directly tested. In this study, we examined how the distinctive multi-bladed morphology of Nereocystis thalli limits drag in flow. We measured drag on whole kelps in a large recirculating flume and quantified how drag was affected by serial removal of blades. We then compared measured drag with predictions of "additive drag", which we defined as the sum of the drag that each blade experiences in isolation. We found that, on average, intact thalli experience only 37% of the predicted additive drag when subjected to a flow rate of 0.40-0.50 m · s-1 . Our results indicate that the subdivision of the photosynthetic area into multiple blades has a drag-reducing effect on Nereocystis thalli. We found drag increases less than proportionally with the cumulative area, meaning the contribution of individual blades to overall drag decreases with increasing blade number. That is, as thalli develop, each additional blade incurs a reduced hydrodynamic cost, perhaps lending insight into how thalli can grow so large.