A simple assay for quantification of plant-associative bacterial nitrogen fixation

Accurate quantification of plant-associative bacterial nitrogen (N) fixation is crucial for selection and development of elite diazotrophic inoculants that could be used to supply cereal crops with nitrogen in a sustainable manner. Because a low oxygen environment that may not be conducive to plant growth is essential for optimal stability and function of the N-fixing catalyst nitrogenase, quantification of N fixation is routinely carried out on “free-living” bacteria grown in the absence of a host plant. Such experiments may not divulge the true extent of N fixation occurring in the rhizosphere where the availability and forms of nutrients such as carbon and N, which are key regulators of N fixation, may vary widely. Here, we present a modified in planta acetylene reduction assay, utilising the model cereal barley as a host, to quantify associative N fixation by diazotrophic bacteria. The assay is rapid, highly reproducible, applicable to a broad range of diazotrophs, and can be performed with simple equipment commonly found in most laboratories that investigate plant-microbe interactions.ImportanceExploiting “nitrogen-fixing” bacteria that reduce atmospheric dinitrogen into ammonia as inoculants of cereal crops has great potential to alleviate current inputs of environmentally deleterious fertiliser nitrogen and drive more sustainable crop production. Accurately quantifying plant-associative bacterial nitrogen fixation is central to the development of such inoculant bacteria, but most assays fail to adequately reproduce the conditions of plant root systems. In this work, we have validated and optimised a simple in planta assay to accurately quantify N fixation in bacteria occupying the root and surrounding soil of the model cereal barley. This assay represents a benchmark for quantification of plant-associative bacterial N fixation.

On soil and technological conditions impact on the parameters of soil moisture zones formed with drip irrigation of tree-fruit crops

Purpose: development of a graphic-analytical method for assessing the effect of soil conditions on moisture contours size formed during drip irrigation to select the parameters of drip modules for irrigating tree-fruit plants cultivated in garden plantations. Materials and methods: the planned dimensions of moisture contours of sub-drip soil space are taken as indicators for assessing and determining the parameters of irrigation modules for drip irrigation of row planted tree-fruit crops from along-row traced irrigation pipelines. When analyzing the parameters and location of moisture zones, the layout of plants in a garden with a distance between trees in a row equal to 2 m was considered, with a different number of drip emitters on the drip line within the inter-tree area. Results: using the author's dependence, the diameters and areas of moisture contours formed during drip irrigation in southern medium-thick chernozems were determined. For typical schemes for placing drip emitters along a row of traced drip lines that provide soil moistening in the undercrown space of fruit plants, moisture contours formed during drip irrigation are built. The obtained geometric parameters of moisture zones for different patterns of irrigation lines, characterized by different inter-emitters distances and different numbers and locations of drip emitters, are compared with the area of plant nutrition. Based on the results of comparing the areas of moisture zone and the zone of plant root systems distribution, a high degree of locality of the wetted space was noted. Conclusions: the graphic images and quantitative characteristics of drip moisture zones in the undercrown along the row space of plants created using the proposed graphic-analytical method allow assessing the state of its moisture content and making a decision on the parameters and schemes of the irrigation module for certain soil and technological conditions of the garden plantation.

Plant Philosophy and Interpretation: Making Sense of Contemporary Plant Intelligence Debates

Plant biologists widely accept plants demonstrate capacities for intelligence. However, they disagree over the interpretive, ethical and nomenclatural questions arising from these findings: how to frame the issue and how to signify the implications. Through the trope of ‘plant neurobiology’ describing plant root systems as analogous to animal brains and nervous systems, plant intelligence is mobilised to raise the status of plants. In doing so, however, plant neurobiology accepts an anthropocentric moral extensionist framework requiring plants to anthropomorphically meet animal standards to be deserving of moral respect. I argue this strategy is misguided because moral extensionism is an erroneous ontological foundation for ethics.

Trichoderma asal akar kopi dari Alor: Karakterisasi morfologi dan keefektifannya menghambat Colletotrichum Penyebab Penyakit Antraknosa secara in Vitro

Trichoderma of coffee roots from Alor: Morphological characteristic and in vitro efficacy to inhibit Colletotrichum, causing Anthracnose Trichoderma is a fungus capable of intimate associations with plant root systems including on coffee plants. This aim of study is to determine the characteristics of Trichoderma morphospecies from coffee roots of Alor origin, East Nusa Tenggara (NTT) and its ability to inhibit the growth of Colletotrichum causing anthracnose disease in-vitro. Root samples of healthy coffee plants were taken from the location of coffee plantations in Alor District, NTT. Isolation of Trichoderma fungi from coffee roots was done by incubating the sterilized coffee roots in a layer of moist filter paper in a Petri dish for seven days. Identification of Trichoderma by observing the characteristics of the colony on the medium of potato dextrose agar (PDA) and microscopic media using microcultures (slide culture). Inhibition of Trichoderma fungi against Colletotrichum was tested by multiple culture methods on PDA media. The results of root incubation in humid conditions showed that there was four morphospecies of Trichoderma fungi, each of which had different characteristic specifications. In vitro antagonism in test on PDA medium, the first three morphospecies against Colletotrichum showed that each Trichoderma could inhibit 70.2%, 65.8%, and 63.3%, respectively, five days after inoculation. This data shows that Trichoderma isolated from coffee roots from Alor has the potential to suppress the growth of anthracnose pathogens.

Restricted Effect of Two Plant Root Systems on the Crack Expansion of China Yunnan Laterite under Dry-wet Cycle

In order to research the restricted effect of hedera nepalensis root systems and heteropogon contortus root systems on the crack expansion of Yunnan laterite under dry-wet cycle, this paper prepares Yunnan laterite with certain moisture content, and makes the compacted samples of pure laterite and composite soil mixed with root systems by adopting hedera nepalensis root systems and heteropogon contortus root systems respectively, and then simulates the dry-wet cycle of laterite in engineering (i.e., rainfalls and evaporations), measures the crack width of samples experiencing different cycles, and makes statistical analysis on the average maximum crack width of samples in all groups by adopting the method of indoor spraying and natural drying. The result indicates that, 10% and 20% mixed hedera nepalensis root systems can exert obvious restrictions on the crack expansion of Yunnan laterite after dry-wet cycle, while 30% mixed hedera nepalensis root systems and 10% mixed heteropogon contortus root systems can also restrict the crack expansion of Yunnan laterite, but the restricted effect is weaker. As for 20% and 30% mixed heteropogon contortus root systems, composite soil samples will disintegrate after the 2nd dry-wet cycle.

Microwave Transmittance Technique Using Microstrip Patch Antennas, as a Non-Invasive Tool to Determine Soil Moisture in Rhizoboxes

Investigating the growth behavior of plant root systems as a function of soil water is considered an important information for the study of root physiology. A non-invasive tool based on electromagnetic wave transmittance in the microwave frequency range, operating close to 4.8 GHz, was developed using microstrip patch antennas to determine the volumetric moisture of soil in rhizoboxes. Antennas were placed on both sides of the rhizobox and, using a vector network analyzer, measured the S parameters. The dispersion parameter S21 (dB) was also used to show the effect of different soil types and temperature on the measurement. In addition, system sensitivity, reproducibility and repeatability were evaluated. The quantitative results of the soil moisture, measured in rhizoboxes, presented in this paper, demonstrate that the microwave technique using microstrip patch antennas is a reliable, non-invasive and accurate system, and has shown potentially promising applications for measurement of rhizobox-based root phenotyping.

Plant Root Systems Preserved in the Permian Cedar Mesa Sandstone at Moki Dugway, Southeastern Utah

Rooted green plants represent the base of the food chain for most terrestrial ecosystems, but, compared to animal burrows, root systems are relatively rarely recognized in ancient sedimentary rocks. Plant roots that penetrate unconsolidated sand dunes, especially those containing not only quartz grains, but also abundant grains of calcite (CaCO) are commonly replaced by fine crystals of calcite (Klappa, 1980). These structures (known by geologists as rhizoliths from the Greek for “root rock”) are one form of calcite cemented soil and sediment called caliche. Caliche crystallizes well above the water table and its calcite crystals are tiny because of rapid evaporation of soil water. One source of the calcium (Ca) and carbonate (CO) ions necessary for making the calcite of caliche is falling dust, and another source is the dissolution of calcite grains already in the soil.

A multi-seasonal model of plant-nematode interactions and its use to identify optimal plant resistance deployment strategies

SummaryRoot-knot nematodes (RKNs) are soil-borne polyphagous pests with major impact on crop yield worlwide. Resistant crops efficiently control avirulent RKNs, but favour the emergence of virulent forms. Virulence being associated with fitness costs, susceptible crops counter-select virulent RKNs. In this study we identify optimal rotation strategies between susceptible and resistant crops to control RKNs and maximize crop yield.We developed an epidemiological model describing the within-season dynamics of avirulent and virulent RKNs on susceptible or resistant plant root-systems, and their between-season survival. The model was fitted to experimental data and used to predict yield-maximizing rotation strategies, with special attention to the impact of epidemic and genetic parameters.Crop rotations were found to be efficient under realistic parameter ranges. They were characterised by low ratios of resistant plants, and were robust to parameter uncertainty. Rotations provide significant gain over resistant-only strategies, especially under intermediate fitness costs and severe epidemic contexts.Switching from the current general deployment of resistant crops to custom rotation strategies could not only maintain or increase crop yield, but also preserve the few and valuable R-genes available to us.