Physiology of medicinal and aromatic plants under drought stress

Drought poses a significant challenge,restricting the productivity of medicinal and aromatic plants.The strain induced by drought can impede vital processes like respiration and photosynthesis,affecting various aspects of plants’growth and metabolism.In response to this adversity,medicinal plants employ mechanisms such as morphological and structural adjustments,modulation of drought-resistant genes,and augmented synthesis of secondary metabolites and osmotic regulatory substances to alleviate the stress.Extreme water scarcity can lead to leaf wilting and may ultimately result in plant death.The cultivation and management of medicinal plants under stress conditions often differ from those of other crops.This is because the main goal with medicinal plants is not only to increase the yield of the above-ground parts but also to enhance the production of active ingredients such as essential oils.To elucidate these mechanisms of drought resistance in medicinal and aromatic plants,the current review provides a summary of recent literature encompassing studies on the morphology,physiology,and biochemistry of medicinal and aromatic plants under drought conditions.

Evaluating land subsidence by field survey and D-In SAR technique in Damaneh City, Iran

Based on the data from piezometers, well logs, geophysical surveys and the interferometric synthetic aperture radar（In SAR） technique, this study investigates the main causes of land subsidence in Damaneh City, Iran. The size, openings and direction of fissures were measured by micrometer and compass. The locations of fissures and wall cracks were determined by GPS. The geoelectrical data were used to determine the composition, thickness, depth and shape of lower parts of the aquifer. Groundwater fluctuations were evaluated by available piezometers. The In SAR technique was used to measure land deformation from space and to map the dense changes of surface displacements. The results indicate that the main cause of ground subsidence is the decline of groundwater heads and changes in composition and thickness of compressible lacustrine sediments. The subsidence map obtained from the radar data of ASAR sensor of ENVISAT satellite shows that the subsidence zone is mainly in northern city that is underlain by very thick fine sediments. The subsidence rates from March to December 2005 and from July 2011 to January 2012 are 6.7 and 7.0 cm/a, respectively. The results also show good correlations among the formation of earth features, decline in groundwater head and thickness of fine-grained sediments. We recommend that the groundwater withdrawal for agricultural and industrial sectors should be restricted and urban expansion in the northern part of the city should be constrained.

Effects of dietary fiber and threonine on performance,intestinal morphology and immune responses in broiler chickens

The present experiment was conducted to investigate the effects of fiber and threonine(Thr)on growth performance,intestinal morphology and immune responses of broiler chickens.A total of 420 one-dayold mixed sex broiler chicks(Ross 308)were randomly divided into 6 experimental diets and 5 replicates of 14 chicks based on a factorial arrangement(2 × 3)from 1 to 42 d of age.Experimental factors included dietary supplemental fiber type(no supplemental fiber[NSF],30 g/kg sugar beet pulp[SBP]or 30 g/kg rice hull[RH])and Thr inclusion level(100% or 110% of Thr requirement recommended by breeder company[Ross 308]).Growth performance of broilers was assayed at different periods of the experiment.Intestinal morphometric features were measured at 21 d of age.Antibody titer against sheep red blood cells(SRBC),Newcastle and influenza disease viruses were measured on d 30 of trial.Dietary inclusion of SBP and RH significantly decreased feed intake and weight gain during the entire rearing period(P<0.05).Interaction of fiber and Thr had no beneficial effects on the performance of chickens across the entire rearing phase.Dietary supplementation of 110% Thr required level improved jejunal morphometric features(P<0.05),whereas its inclusion with fibrous materials failed to show the same effects.Dietary supplemental Thr together with SBP significantly increased antibody production against SRBC(P<0.05).In conclusion,although supplemental 30 g/kg fibrous materials impaired growth performance,inclusion of SBP along with 110% Thr level improved the humoral immunity in broiler chickens.

Spatial downscaling of climate variables using three statistical methods in Central Iran

Spatial downscaling methods are widely used for the production of bioclimatic variables(e.g. temperature and precipitation) in studies related to species ecological niche and drainage basin management and planning. This study applied three different statistical methods, i.e. the moving window regression(MWR), nonparametric multiplicative regression(NPMR), and generalized linear model(GLM), to downscale the annual mean temperature(Bio1) and annual precipitation(Bio12) in central Iran from coarse scale(1 km × 1 km) to fine scale(250 m ×250 m). Elevation, aspect, distance from sea and normalized difference vegetation index(NDVI) were used as covariates to create downscaled bioclimatic variables. Model assessment was performed by comparing model outcomes with observational data from weather stations. Coefficients of determination(R2), bias, and root-mean-square error(RMSE) were used to evaluate models and covariates. The elevation could effectively justify the changes in bioclimatic factors related to temperature and precipitation. Allthree models could downscale the mean annual temperature data with similar R2, RMSE, and bias values. The MWR had the best performance and highest accuracy in downscaling annual precipitation(R2=0.70; RMSE=123.44). In general, the two nonparametric models, i.e. MWR and NPMR, can be reliably used for the downscaling of bioclimatic variables which have wide applications in species distribution modeling.