A field experiment was conducted to determine the sensitivity of wheat to water stress and changes in water relations and yield of wheat (Triticum aestivum L.) under water stress conditions applied at different growth stages. The experiment comprised of two wheat cultivars and four water stress treatments, maintained by withholding water at tillering, anthesis, and at both stages. Water stress caused reduction in leaf relative water contents, water potential, osmotic potential, turgor potential, growth and yield components of both the wheat cultivars. The results indicated that high value of relative water contents were associated with increased yield and yield components. Consecutive stresses at both growth stages caused severe reduction in yield and yield components in both cultivars of wheat. Keywords: Water stress; water relations; growth; Triticum aestivum; yield components. DOI: http://dx.doi.org/10.3329/bjar.v36i3.9264 BJAR 2011; 36(3): 455-468
Limited water availability hampers the sustainability of crop production. Exogenous application of glycinebetaine (GB) and salicylic acid (SA) has been found very effective in reducing the adverse effects of water scarcity. This study was conducted to examine the possible role of exogenous GB and SA application in improving the growth and water relations of hybrid sunflower (Helianthus annuus L.) under different irrigation regimes. There were three levels of irrigation, viz. control (normal irrigations), water stress at budding stage (irrigation missing at budding stage) and water stress at flowering stage (FS) (irrigation missing at FS). GB and SA were applied exogenously at 100 and 0.724 mm respectively, each at the budding and FS. Control plants did not receive application of GB and SA. Water stress reduced the leaf area index (LAI), leaf area duration (LAD), crop growth rate (CGR), leaf relative water contents, water potential, osmotic potential, turgor pressure, achene yield and water use efficiency. Nevertheless, exogenous GB and SA application appreciably improved these attributes under water stress. However, exogenous GB application at the FS was more effective than other treatments. Net assimilation rate was not affected by water stress as well as application of GB and SA. The protein contents were considerably increased by water stress at different growth stages, but were reduced by exogenous GB and SA application. The effects of water stress and foliar application of GB were more pronounced when applied at FS than at the budding stage. Moreover, exogenous GB application was only advantageous under stress conditions.
A field experiment was conducted to study the response of two maize hybrids to external K application under saline field conditions (ECe 5.71-8.91 dS m-1). The data showed that there was an increase in the different growth and yield components with the increase in the external K. The increase was more pronounced when K was applied at the rate of 175 kg ha-1 with respect to control treatment. The enhanced growth and yield of these hybrids under saline conditions might be due to the response of K application, resulting in reduced Na uptake. The results indicated that the hybrids Pioneer 32B33 perform better than Dekalb 979 and economical yield can be obtained when potassium was applied at the rate of 125 kg ha-1.
INTRODUCTIONSalinity stress reduces the plant growth productivity and efficiency of crops around the world (Machado & Serralheiro, 2017) and affects more than 800 million ha of land in the world which is equal to 6% of the whole world (FAO, 2011). Crops grown on salt affected areas undergo high osmotic stress, ionic toxicities, poor physical conditions of soil and decreased production (Shrivastava & Kumar, 2015). Salinity is one of the major environmental issue influencing plant development and efficiency (Ahanger et al., 2017;Allakhverdiev, Sakamoto, Nishiyama, & Murata, 2000). It has been estimated that in salinity stressed soils, the concentration of Na + and Clis higher accompanied with the decreased concentration of K + and K + : Na + ratio thus adversely affecting the plant growth (Saqib, Akhtar, & Qureshi, 2004). Salt stress affects plant ARTICLE INFO
Aeolesthes sarta (Solsky 1871) (Coleoptera: Cerambycidae) is a polyphagous longhorned beetle species that primarily damages broadleaved tree species. This pest is distributed in the western and northern regions of Pakistan, where it caused serious damage to Populus spp. plantations. However, the growth and dispersal patterns of insects and pests are changing due to climate change. Modeling the range expansion or contraction of A. sarta development regions in Pakistan was the goal of the current study, assuming climate change might influence the geographical distribution of A. sarta in Pakistan. Under historical and future climatic conditions, A. sarta distribution areas were estimated using the CLIMEX model. Three time periods, 2030 (early century), 2070 (late century), and 2100 (end century), were forecasted for habitat suitability using the two climate change scenarios (CCSs) A1B and A2. Under the historic climatic condition (HCC), A. sarta was distributed in most areas of Pakistan, and its optimum habitat accounted for 71.67% of its total potential distribution. In the early-century period, optimum habitat dropped to 50.60% and 52.22% under A1B and A2 scenarios in the suitable condition. In the late-century period, optimum habitat further reduced to 31.76% and 30.60% under A1B and A2 scenarios. Moreover, at the end-century period, severe range shrinkage was predicted in the optimum habitat (19.99% under both CSSs). The model predicted a shift in the suitable habitat areas for A. sarta to the west and north. Furthermore, most climatically suitable areas under historic conditions became unsuitable during the end-century period. These projected results will assist in identifying the impacts of global warming on the possible distribution of A. sarta, thereby offering vital information for developing early forecasting and pest-prevention techniques to prevent further loss of forest and woodland trees.
Aeolesthes sarta or Trirachys sarta is a polyphagous long-horned beetle that has caused severe damage to the Populus alba forests/plantations in its regions of origin. Climate change could accelerate the introduction and spread of invasive pest species, potentially causing ecological damage and economic losses. Furthermore, globalization and increased trade can inadvertently transport pests across borders into regions where they do not already occur. Hence, it is crucial to identify areas where the climate is most suitable for the establishment of A. sarta’s and which areas of the world are suitable for the growth of P. alba under climate change scenarios. This study employed the CLIMEX model to estimate the potential global distribution of A. sarta and its correlation with its dominant host, P. alba, under current climatic conditions and potential future scenarios, namely the A1B and A2 climate change scenarios (CCSs). Under current climatic conditions, the model indicates that the establishment of a climatically suitable habitat for A. sarta extends beyond its current known range. The model estimated that, under the world’s current climatic conditions, 41.06% of the world can provide suitable areas (EI > 0) for the survival of A. sarta. For P. alba, under the current climatic conditions, suitable regions for the growth of P. alba are present in all continents (excluding Antarctica); under the world’s current climatic conditions, 53.52% of the world can provide suitable areas for the growth of P. alba (EI > 0). Climate change will significantly alter the number of suitable habitats for A. sarta development and P. alba growth globally. In future climatic conditions, the number areas capable of supplying suitable habitats (EI > 0) for A. sarta will slightly decrease to 40.14% (under A1B and A2 CCSs), while, for P. alba, the number areas capable of supplying suitable habitats will also marginally decrease to 50.39% (under A1B scenario), and this figure is estimated to drop to 48.41% (under A2 scenario) by the end century (2100). Asia, Europe, North America, South America, and Oceania have a high percentage of highly suitable areas for A. sarta development and P. alba growth under current climatic conditions; however, according to estimates of future climatic conditions, by the end century, only Asia, Europe, North America, and Oceania will have a high percentage of highly suitable areas for A. sarta development and P. alba growth. The range of highly suitable habitats is likely to increase in the northern hemisphere; however, this range is expected to shrink with regards to the southern hemisphere. The range contraction was higher under the A2 climate change scenario due to a higher warming trend than in the A1B scenario. Due to climate change, the range of A. sarta development shifted, as did the P. alba growth range, which, thanks to the suitable environmental conditions for the growth of P. alba, makes all those regions vulnerable to the introduction and development of A. sarta. Strict monitoring, prevention, and control measures at borders, airports, and seaports before the trade of P. alba and other suitable host species wood (logs/billets) are highly recommended to prevent the spread of A. sarta and ensure biodiversity security. It is expected that the A. sarta and P. alba climate models presented here will be useful for management purposes since both can be adapted to guide decisions about imparting resources to regions where the threat of pest invasion remains and away from regions where climate suitability is predicted to decrease in the future.
Limited water availability is a severe threat to the sustainability of crop production. Exogenous application of glycinebetaine (GB) has been found very effective in reducing the adverse affects of water scarcity. This study was conducted to examine the role of exogenous GB application in improving the yield of hybrid sunflower (Helianthus annuus L.) under different irrigation regimes. There were three levels of irrigation: Control (four irrigations), three irrigations (irrigation missing at budding stage) and two irrigations (irrigation missing at budding and grain formation stage) in the experiment. While GB was applied exogenously at 100 mM GB each at budding and grain formation stages, the Control treatment did not receive any GB application. Data regarding yield, yield components and quality parameters showed that water stress reduced the head diameter, number of achene per head, 1000-achene weight and yield. Nonetheless, it was significantly improved by the exogenous GB application. Among the qualitative characteristics, protein contents were significantly increased by water stress at different growth stages but were reduced by exogenous GB application. Whilst oil contents were reduced by drought at different stages, GB application, however, did not ameliorate the negative effect of drought stress on achene oil contents. The effects of water stress and foliar application of GB were more pronounced when applied at vegetative stage than at the reproductive stage. Moreover, exogenous GB application was only advantageous under stress conditions.
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