Changes in minimum winter temperature (MWT) and their potential effects on plant growth and development have been gaining increased scientific attention. To better understand these changes across long temporal scales, the present study used dendroclimatological techniques to assess variations in MWT in Southwestern China. Using data from Rhododendron species distributed in areas above the tree-line, a regional composite chronology was generated for a 341-year period. Based on the significant negative correlation between MWT values and ring-width, the most reliable parts of this chronological data were then used to reconstruct MWT values for the past 211 years. This reconstructed MWT series showed decadal to multi-decadal fluctuations. Three distinct cold periods prevailed during 1823–1858, 1882–1891 and 1922–1965, while four warm intervals occurred in 1800–1822, 1858–1881, 1892–1921 and 1966–2011. Our reconstructed MWT reveals a warming trend over the most recent eight decades, which is in agreement with instrumental observations. However, the MWT values and rate of warming over the past seven decades did not exceed those found in the reconstructed temperature data for the past 211 years. Spatial correlations reveal that the MWT in Southwest China is strongly associated with regional temperatures in the Eastern and Central Himalaya, Northern China, and the Indian Peninsula. Larger scale climate oscillations of the Western Pacific and Northern Indian Ocean as well as the North Atlantic Oscillation probably influenced the region’s temperature in the past.
Tag: plant growth
Partitioning the contributions of biochar properties to enhanced biological nitrogen fixation in common bean (Phaseolus vulgaris)
Studies document increases in biological nitrogen fixation (BNF) following applications of biochar. However, the underlying mechanisms for this response remain elusive. Greenhouse experiments were conducted to test the effects of biochar mineral nutrients, pH, and volatile matter (VM) on BNF in common beans (Phaseolus vulgaris L.). Biochars were produced from seven feedstocks pyrolyzed at either 350 or 550 °C. Biochars were treated with acid to reduce mineral nutrient contents, with acetone to remove acetone-soluble VM, with steam to reduce both the mineral and VM contents, or left untreated. The biochar additions at a rate of 15 t ha1 resulted in an average 262 % increase in shoot biomass, 164 % increase in root biomass, 3575 % increase in nodule biomass, and a 2126 % increase in N derived from atmosphere (Ndfa) over the control. Simple mineral nutrients and soil acidity amelioration from the biochar were only to a minimal extent responsible for these increases (r2=0.03; P=0.0298, n=201). Plant growth and Ndfa were significantly correlated with plant P uptake (r2=0.22; P0.05). Improved P nutrition resulted from 360 % greater mycorrhizal colonization with biochar additions. Removal of acetone-soluble VM increased plant growth and Ndfa, and VM extracted from the biochar produced at 350 °C reduced the growth of rhizobia in yeast extract mannitol agar (YMA) medium. In contrast, acetone-soluble VM extracted from seven biochars produced at 550 °C increased the growth of rhizobium in the YMA compared to an acetone-residue control, suggesting differential effects of VM forms on rhizobia.
Phytoremediation potential evaluation of three rhubarb species and comparative analysis of their rhizosphere characteristics in a Cd- and Pb-contaminated soil
Screening or breeding exceptional plant species for heavy metal phytoremediation is as important as adopting feasible measures to enhance phytoremediation efficiency, which are largely based on clarifying the mechanisms of heavy metal tolerance and accumulation by plants. In this study, cadmium (Cd) and lead (Pb) tolerance and accumulation characteristics of Rheum officinale, R. palmatum, and R. tanguticum were analysed to assess their phytoremediation potential. The seed germination test indicated that these three rhubarb species could tolerate 10 mg L−1 Cd and 100 mg L−1 Pb. However, when sown in Cd- and Pb-contaminated soil, all three rhubarb species exhibited a relatively high Cd accumulation capacity but a considerably low Pb accumulation capacity according to the bioconcentration factors of Cd (0.42–0.47 in shoots and 0.11–0.15 in roots) and Pb (0.004–0.008 in shoots and 0.007–0.013 in roots). The high Cd translocation factors (3.04–4.24) indicated that these three rhubarb species were suitable for Cd phytoextraction. The changes in rhizospheric physicochemical indices were generally similar among the three rhubarb plants in comparison with those of the unplanted soil. However, differential indicator rhizobacteria were identified for the three rhubarb plants, which may be primarily attributed to their different root system characteristics. These enriched rhizobacteria included many plant growth-promoting bacteria, and several of them were also involved in regulating heavy metal uptake by plants, indicating that three rhubarb species likely recruit differentially beneficial rhizobacteria to maintain plant growth and vitality and to regulate heavy metal uptake in the Cd- and Pb-polluted soil. This study identifies new candidate plant resources for the phytoremediation of Cd-polluted soils and provides novel insights into understanding the interactions among heavy metals, rhizobacteria, and plants.
Microplastics as an emerging threat to plant and soil health in agroecosystems
Microplastics (MPs, <5 mm in diameter) have been widely recognized as a critical environmental issue due to their extensive use and low degradation rate. Based on current evidence, our aim is to evaluate whether MPs represent an emerging threat to plant-soil health in agroecosystems. We assess the ecological risks to plant-microbe-soil interactions associated with MPs and discuss the consequences of MPs on soil carbon (C), nutrient cycling, as well as greenhouse gas emissions in agroecosystems. We also identify knowledge gaps and give suggestions for future research. We conclude that MPs can alter a range of key soil biogeochemical processes by changing its properties, forming specific microbial hotspots, resulting in multiple effects on microbial activities and functions. Mixed effects of MPs on plant growth and performance can be explained by the direct toxicity of MPs or the indirect alteration in soil physical structures and microbial communities (i.e. symbiotic arbuscular mycorrhizal fungi). Because of the diverse nature of MPs found in soils, in terms of polymer type, shape and size, we also see differing effects on soil organic matter (SOM) decomposition, nutrient cycling, and greenhouse gases production. Importantly, increased bioavailable C from the decomposition of biodegradable MPs, which enhances microbial and enzymatic activities, potentially accelerates SOM mineralization and increases nutrient competition between plant and microbes. Thus, biodegradable MPs appear to pose a greater risk to plant growth compared to petroleum-based MPs. Although MPs may confer some benefits in agroecosystems (e.g. enhanced soil structure, aeration), it is thought that these will be far outweighed by the potential disbenefits.
The influence of seed transfer distance on the growth of Calotropis procera (ait) provenances in dry lands of South Eastern Kenya
In a study to domesticate the species Calotropis procera, for wool production in drylands, investigations were done to determine the effects of seed transfer distance on the growth of the species in a typical farm setting. The objectives of the research were to determine the growth of three provenances of C. procera and to determine the influence of seed transfer distance on the growth parameters. Diameter and height data were used to generate horizontal and vertical growth curves respectively and further subjected to Duncan Multiple Range Test (DMRT) to isolate existence of significant differences across the three provenances. Pearson correlation analysis was used to establish existence of relationships across the growth parameters. Results showed that C. procera is a multi-stemmed plant. Duncan Multiple Range Test (DMRT) showed no significant statistical differences (p<0.5) in diameter growth though Pearson correlation analysis, showed strong positive correlations (Pearson, p<0.01) between branching and DBH Test of homogeneity of variances showed significant statistical differences (p<0.5) in vertical growth The study concluded that C. procera is a multi-stemmed plant that can reach a height of 4.48m and a diameter of 7.4cm in two years. It is recommended that C. procera seeds for raising nursery stock should be sourced from the nearest source possible. This will reduce the environmental and climatic effects associated with long distance seed transfers and ensure the species benefits from home-site advantages.
Endophytic fungi from oncosperma sp. With promising in vitro plant growth promotion and antagonistic activities
This study was conducted to identify in vitro plant growth promoting traits and antagonistic activities of endophytic fungi from Oncosperma sp. Sixty-two endophytic fungi were isolated from leaves, roots, petioles, and spines of Oncosperma sp. Ten strains [Colletotrichum sp. (1), Daldinia spp. (6), and Diaporthe spp. (3)] showed efficient plant growth-promoting traits as well as in vitro antagonistic activities. Daldinia strains MFLUCC 20-0215, MFLUCC 20-0211, and MFLUCC 20-0210 produced higher Indole-3-acetic acid (IAA) concentrations of 120.3, 96.5, and 87.5 µg/mL, respectively. Quantitative estimation of phosphate solubilization for these taxa ranged between 2.6-3.6. A dual culture technique was used to determine the in vitro antagonistic activities against pathogenic strains of Colletotrichum sp. isolated from oil palm and coffee, and Corynespora sp. from tomato. Daldinia strains MFLUCC 20-0207 and MFLUCC 20-0216 showed strong antifungal activities with 60.6-87.3% inhibition. Diaporthe strains MFLUCC 20-0206, MFLUCC 20-0208 and MFLUCC 20-0214, and Daldinia strains MFLUCC 20-0210, 20-0211, and 20-0215 exhibited moderate antifungal activity against all test pathogens. Endophytic fungi associated with Oncosperma produced positive results in plant growth activities and biocontrol potential, providing a base for further investigation. Three isolates of Daldinia (MFLUCC 20-0210, MFLUCC 20-0211, MFLUCC 20-0125) were especially promising due to their significantly high IAA production, highest phosphate solubilization, and moderate antagonistic activities. Thus, future research should focus on Daldinia as they possess great potential for a wide range of applications. © 2021, Chiang Mai University. All rights reserved.
Population dynamics of Hippophae rhamnoides shrub in response of sea-level rise and insect outbreaks
The coastal vegetation of islands is expected to be affected by future sea-level rise and other anthropogenic impacts. The biodiverse coastal vegetation on the eastern part of the Dutch Wadden Island of Ameland has experienced land subsidence caused by gas extraction since 1986. This subsidence mimics future sea-level rising through increased flooding and raising groundwater levels. We studied the effects of this relative sea-level rise and other environmental factors (i.e. insect outbreaks, temperature and precipitation) on the population dynamics (i.e. cover and age structure and annual growth) of the shrub seabuckthorn (Hippophae rhamnoides L.) in young (formed after 1950) and old (formed before 1950) dune areas over a period of 56 years (1959–2015). We found an increase in seabuckthorn cover in the young dune areas since 1959, while over time the population in the old dunes decreased due to successional replacement by other species. With the increasing age of the young dunes, we found also a decrease in sea-buckthorn after 2009. However the sharp decrease indicated that other environmental factors were also involved. The most important determinant of annual shrub growth appeared to be five outbreaks of the brown-tail moth (Euproctis chrysorrhoea L.), in the last decade. Relative sea-level rise caused more frequent flooding and reduced growth at lower elevations due to inundation or soil water saturation. This study clearly indicates that sea-buckthorn is affected by relative sea-level rise, but that other ecological events better explain its variation in growth. Although shrub distribution and growth can be monitored with robust methods, future predictions of vegetation dynamics are complicated by unpredictable extreme events caused by (a)biotic stressors such as insect outbreaks.
Effects of Climate Smart Agricultural practices and Planting Dates on Maize Growth and Nutrient Uptake in Semi-Arid Tanzania
The shift of growing season’s onset due to rainfall and seasonal variability are among the climate change impacts affecting agricultural productivity in semi-arid. Previous studies have also noted the seasonal variations in planting windows in semi-arid Tanzania. Because of such rainfall variability due to uncertainties of climate change, farmers face difficulties in determining the appropriate planting dates. Though, climate-smart agriculture (CSA) practices are reinforced to mitigate such climatic extremes and sustain crop production, there is limited information on the performance of CSA practices under the uncertainty of planting windows due to unpredictable rainfall on-set and patterns. This study assessed the effects of CSA practices at different planting windows on maize growth and nutrient uptakes at Mlali village of Dodoma, Tanzania. A split-plot experimental design was adopted, treatments involved CSA practices (Chololo pits, tied ridges, intercropping and Ox-cultivation – as a control) and/at planting windows (Early, Normal and Late planting). The planting windows were determined based on previous studies and Tanzania national weather forecasts. The results showed that, CSA practices had a significant (p < 0.05) effect on maize height and N nutrient uptake. Similar biomass and Mg nutrient uptake were significantly affected (p < 0.05) by both CSA practices and planting dates though Leaf Area Index (LAI) were significantly affected (p < 0.05) by planting windows. Chololo pits and tied ridges and late planting dates had the highest soil moisture, plant heights, and biomass. Ox-cultivation had a slight high N, K and Mg nutrient uptake followed with Chololo pits and tied ridges.