A New Approach of Canopy Temperature based Irrigation Scheduling of Wheat in Humid Subtropical Climate of India

Proceedings of the National Academy of Sciences, India Section B: Biological Sciences - The aim of the study is to develop a new canopy temperature based index named plant stress index (PSI) as an...     

Assessment of Water Status in Wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) Using Ground Based Hyperspectral Reflectance

Field experiments were conducted with four levels of irrigation and nitrogen on wheat for 2 years (2009–2010 and 2010–2011) to quantify and predict the crop water status using hyperspectral remote sensing. Hyperspectral reflectance in 350–2500 nm range was recorded at five growth stages. Based on highest correlation between relative leaf water content (RLWC) and reflectance in five water bands, the booting stage was identified as the most suitable stage for water stress evaluation. Ten hyperspectral water indices were calculated using the first year booting stage reflectance data and prediction models for RLWC and equivalent water thickness (EWT) based on these ten indices were developed. The prediction models for RLWC based on moisture stress index (MSI), normalized difference infrared index (NDII), normalized difference water index₁₆₄₀ (NDWI₁₆₄₀) and normalized multi-band drought index (NMDI) were identified as the most precise and accurate models as indicated by different validation statistics. The models developed for EWT based on water band index (WBI), MSI, NDWI₁₆₄₀ and NMDI were found to be most suitable and accurate. These indices were found to be insensitive to N stress treatments indicating their ability to detect water deficiency as the cause of plant stress. Thus, the study identified four hyperspectral water indices to assess the wheat crop water status at booting stage and developed their respective predictive models.     

Determination of anthelmintic activity of the leaf and bark extract of tamarindus indica linn

The aim of the present study was to evaluate the anthelmintic activity of ethanolic and aqueous extract of leaves and bark of Tamarindus indica Linn using Pheretima posthuma and Tubifex tubifex as test worms. The time of paralysis and time of death were studied and the activity was compared with piperazine citrate as reference standard. The alcohol and aqueous extract of bark of Tamarindus indica exhibited significant anthelmintic activity as evidenced by decreased paralyzing time and death time. The results thus support the use of Tamarindus indica as an anthelmintic agent.     

Patterns of bacterial motility in microfluidics-confining environments

Understanding the motility behavior of bacteria in confining microenvironments, in which they search for available physical space and move in response to stimuli, is important for environmental, food industry, and biomedical applications. We studied the motility of five bacterial species with various sizes and flagellar architectures (Vibrio natriegens, Magnetococcus marinus, Pseudomonas putida, Vibrio fischeri, and Escherichia coli) in microfluidic environments presenting various levels of confinement and geometrical complexity, in the absence of external flow and concentration gradients. When the confinement is moderate, such as in quasi-open spaces with only one limiting wall, and in wide channels, the motility behavior of bacteria with complex flagellar architectures approximately follows the hydrodynamics-based predictions developed for simple monotrichous bacteria. Specifically, V. natriegens and V. fischeri moved parallel to the wall and P. putida and E. coli presented a stable movement parallel to the wall but with incidental wall escape events, while M. marinus exhibited frequent flipping between wall accumulator and wall escaper regimes. Conversely, in tighter confining environments, the motility is governed by the steric interactions between bacteria and the surrounding walls. In mesoscale regions, where the impacts of hydrodynamics and steric interactions overlap, these mechanisms can either push bacteria in the same directions in linear channels, leading to smooth bacterial movement, or they could be oppositional (e.g., in mesoscale-sized meandered channels), leading to chaotic movement and subsequent bacterial trapping. The study provides a methodological template for the design of microfluidic devices for single-cell genomic screening, bacterial entrapment for diagnostics, or biocomputation.

Many motile bacteria live in confining microenvironments (e.g., animal or plant tissue, soil, waste, granulated, and porous materials) and consequently are important to many applications like health [infectious diseases (1, 2), pharmaceuticals (3), and nutrition (4)], agriculture [veterinary (5) and crops (6)], environmental science [photosynthesis (7), biodegradation (8), and bioremediation (9)], and industrial activities [mining (10) and biofouling (11)]. Bacterial motility is essential in the search for available physical space as well as for enabling bacterial taxis in response to external stimuli, such as temperature (12), chemical gradients (13, 14), mechanical cues (15), or magnetic fields (16).To thrive in environments with diverse geometrical and physical characteristics, from open spaces to constraining environments, motile bacteria have evolved a multitude of propelling mechanisms (17), with flagellum-driven being the most common (18, 19). Flagellum-based machinery features various numbers of flagella (20) and designs: monotrichous, lophotrichous, amphitrichous, or peritrichous. The mechanics of this machinery, coupled with cell morphology (21) (e.g., coccus, rod-like, or curved) translates into several motility modes (e.g., turn angle, run-and-tumble, or run-and-flick) (22), and various motility behaviors (e.g., swimming, tumbling, and swarming) (17, 23). Environmental factors (24, 25) (e.g., chemical composition, viscosity, temperature, pH, and the chemistry and the roughness of adjacent surfaces) also influence bacterial motility.“Pure” bacterial motility, unbiased by chemotaxis or fluid flow, was reported near simple flat surfaces (26, 27) and in channels (28–30). Simulations of model bacteria in analogous conditions were also undertaken (31–37), but owing to the complexity of bacterial mechanics (38), modeling from first principles did not provide sufficient understanding to accurately predict movement patterns of different species in complex, confined environments. Consequently, studies of the effects of bacterial geometry in confined geometries were limited to models of simple, monotrichous bacteria with an assumed rigid flagellum (32, 39).Microfluidic devices (40, 41) are commonly used for the manipulation of individual or small populations of cells in micrometer-sized channels for medical diagnostics (42), drug screening (43), cell separation (44, 45), detection and sorting (46), and single-cell genomics (47). While microfluidic structures are used for the study of the motility of mammalian cells (48, 49), and microorganisms [e.g., fungi (50, 51), algae (52), or bacteria (29, 53–56)], these studies typically focus on a single species.To make progress toward a more general understanding of the motility of individual bacterial cells in confining microenvironments, as well as to assess the extent to which the behavior of bacteria with complex architectures can be assimilated with that of the more predictable monotrichous bacteria, the present work investigated the movement of five species (i.e., Vibrio natriegens, Magnetococcus marinus, Pseudomonas putida, Vibrio fischeri, and Escherichia coli) in microfluidic geometries with various levels of confinement and geometrical complexity.