Abstract
Nitrogen is one of the most important macro-nutrients for plant growth and crop productivity. The amount of synthetic nitrogen fertilizers supplied to crops has dramatically increased, leading to a notable rise in crop yields. However, excessive nitrogen use has an enormous negative impact on ecosystems and human health through the emission of intense greenhouse gases, such as nitric oxide derived from the nitrate (NO3–) assimilation cascade. Additionally, owing to the development of extensive irrigation in agriculture, crops are known to suffer from high salt stress. The effect of excessive nitrogen fertilizer application has been studied in some crops, but the effect of high nitrate level and salt stress on plant stress tolerance has not been studied in detail. Therefore, in this study we aimed to study the effects of high concentrations of NO3– on salt stress tolerance in Arabidopsis. In addition, since anthocyanin functions as a reactive oxygen species (ROS) scavenger under abiotic stress conditions, we investigated whether enhanced anthocyanin content helps Arabidopsis to withstand higher salt stress levels under high NO3– concentrations by using pap1-D/fls1ko double mutant plants, which accumulate excessive amount of anthocyanin. We found that Col-0 plants are more sensitive to salt stress under high NO3– concentrations. Although both the pap1-D/fls1ko and fls1ko plants accumulated higher anthocyanin levels and radical scavenging activities than Col-0 plants under both normal and salt stress conditions, the fls1ko plants exhibited much better growth than the pap1-D/fls1ko plants. It appears that the enhanced NR activities and transcript levels of NIA1 and NIA2 in pap1-D/fls1ko and fls1ko plants led to an increase in the synthesis of proteins and proline, which increases osmolytes against salt stress. Our results demonstrate that optimal levels of anthocyanin accumulation can enhance growth performance of plants under high NO3– and salt stress conditions.
Highlights
The demand for high quality vegetable crops has steadily increased due to global population growth and the rapid pace of economic development
As shown in Figure 1C), treatment with high NO3− concentration and 175 mM NaCl resulted in decreased chlorophyll contents in all plant types we examined, PRODUCTION OF ANTHOCYANIN PIGMENT 1-dominant (pap1-D)/fls1ko and fls1ko plants accumulated more chlorophyll contents compared with Col-0 and ttg1ko plants
We aimed to investigate whether the mutant plants that over-produce anthocyanins were better than Col0 in terms of tolerance to high-salt stress in the presence of high NO3−
Summary
The demand for high quality vegetable crops has steadily increased due to global population growth and the rapid pace of economic development. Constant single crop cultivation and, excessive nitrogen fertilizer application change the transformation process of soil nitrogen and accelerate the accumulation of NO3− (Shen, 2010; Li et al, 2015). This causes serious environmental pollution (Schlesinger, 2009), but may impact the stress tolerance and productivity of the plant itself. As the development and use of smart farm systems in plant factory technology progress, it is necessary to study the optimization of nitrogen fertilizer application required for the production of crops suitable for a specific purpose
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