How does nitrate affect plant growth

Figure 1. Each treatment had three biological replicates and the assays were repeated three times. As shown in Figure 1D , K levels also significantly affected root activity. The highest root activity appeared in 6 mM K treatment, and inappropriate K levels had a negative effect on root activity. Potassium content in the roots, stems, and leaves of seedlings increased with the increasing in K supply Figure 2.

The K content of all organs was the highest under K12 treatment. In K0 and K3 treatments, the K content of each organ was the highest in leaves, second-highest in the stems, and lowest in roots. Under the other K level treatments, the K content of each organ was highest in the roots and lowest in the stems. So, K was preferentially supplied to the shoot under low K conditions. Figure 2. We monitored photosynthetic rate and gas exchange parameters to determine possible effects of different K levels.

With increasing K supply, P n and G s increased first and then decreased Table 3 , reaching the maximum value in K6 treatment. However, C i was the highest in K0 treatment and the lowest in K6 treatment. Table 3. Chlorophyll fluorescence was further investigated to understand the internal causes of the effects of different K levels on photosynthesis.

This indicates that unsuitable K levels can inhibit photosynthetic electron transfer, increase heat dissipation and even damage the light system K0 treatment. As shown in Figure 3 , after 30 days, seedlings subjected to K6 treatments acquired the highest activities of Rubisco, SPS and SS, followed by K9 treatments, and K0 treatments obtained the lowest activities. These results indicate that low or high K levels can significantly inhibit the activity of C metabolizing enzymes in leaves, and the inhibition effect is more significant under low K levels than that under high K levels.

Figure 3. The 13 C accumulation rate in all organs of seedlings under the K6 treatment were significantly higher than those under of other treatments Figure 4A. Figure 4. The distribution ratio of 13 C to each organ is related to its competitive ability but also chiefly to its transport capacity within the plant. The 13 C distribution rates for each treatment were consistent in both years, among which the leaves had the highest values followed by the stems, and roots Figure 4B.

K supply increased the 13 C distribution rate in roots, which increased first and then decreased with increasing K levels. An different trend was, however, observed for leaves. No significant effect was observed on the 13 C distribution ratio in stems under K treatments. The NO 3 — ion flow velocity in roots increased at first as K supply rose, but then decreased, which implied that a moderate K supply level will promote nitrate ions to be take up by roots Figure 5.

In and , the average NO 3 — flux rates within 10 min of seedling root exposure to K6 treatment increased by Figure 5. A Net NO 3 — fluxes in the root of apple seedlings for 10 min.

B Mean rate of NO 3 — fluxes during the entire 10 min. Compared with roots, NR activities in leaves were significantly affected by K levels Figure 6 , and NR activities in leaves under the K6 treatment were significantly higher than the other treatments for all three stages Figure 6A , which improved nitrate assimilation capacity.

In contrast, NR activities in the leaves under the K0 and K12 treatments were relatively lower. Unlike NR activities, differences in GS activities in roots was greater between different K treatments than that in leaves Figures 6C,D , and the higher values appeared in the K6 treatment.

Figure 6. We compared the effects of the different K supply levels on NRT1. As expected, we found that NRT1. Figure 7. After 30 days of treatment, the 15 N absorption rate of seedlings in K6 treatment was significantly higher than that of the other treatments, and the 2-year average was 1.

Figure 8. The 15 N use efficiency was calculated from the 15 N absorption content divided by the total 15 N application rate. Potassium has a significant effect on the growth and development of plant roots. Jung et al. Therefore, plants can cope with short-term K deficiency by promoting root growth. However, compared with the lack of N and phosphorus, the growth of plant roots is strongly inhibited under conditions of prolonged K deficiency, and the root-shoot ratio will be significantly reduced Hermans et al.

However, root growth was significantly inhibited by unsuitable K supply levels, which may be due to an increase in ethylene and a decrease in indoleacetic acid IAA in the roots Zhang et al. At the same time, the limited transport of photosynthetic products from leaves to roots may also explain why unreasonable K supply hinders root growth Figure 4B. The percentage of 15 N in each organ accounting for the total 15 N content reflects the distribution of N fertilizer in the seedlings and the migration regularity in the organs.

And, the opposite trend exhibited in the leaves Figure 8B. This suggested that the K level can affect root-to-leaf transportation. Potassium status of plants has a significant effect on the transport and distribution of photosynthetic products Pettigrew, Sufficient K supply can establish osmotic potential in the phloem and help to transfer photosynthates from source to sink organs Cakmak, However, the loading of photosynthates in phloem of K deficient plants is inhibited and the transport to roots is significantly reduced Gerardeaux et al.

In this study, the 13 C isotope labeling results showed that the 13 C assimilation rate and distribution ratio in roots were higher under an appropriate K supply level. This indicates that insufficient or excessive K supply can inhibit the C assimilation of leaves and the photosynthetic products transport from leaves to roots.

Correlation analysis also showed that the 13 C distribution ratio was positively correlated with root biomass. Meanwhile, the 13 C distribution ratio of roots was significantly positive related to photosynthesis and C metabolizing enzyme activity SS and SPS activities.

We also measured the gas exchange parameters of leaves, and found that the P n and G s of seedling decreased significantly under the treatment of low and high K supply, which indicates that inappropriate K supply would limit photosynthesis through stomatal restrictions.

C i increased significantly under K0 treatment, therefore, the decrease of P n may also be related to limitations of the optical system. These results clearly show that K deficiency or excess can inhibit the photochemical efficiency and electron transfer efficiency of PSII reaction center. Lu et al. In conclusion, we showed that K affected C assimilation and distribution by regulating photosynthesis and C metabolizing enzymes.

The increase in the distribution of photosynthetic products to the root system will promote growth and development of the root system, then improving the absorption ability of N, thus increasing NUE. Parker and Newstead showed that NRT1. Li et al. In addition, an ideal root morphology and activity were important for nutrient absorption Sattelmacher et al. As a result, a higher 15 N absorption content appeared under appropriate K supply conditions Figure 8.

In addition, K also affected the distribution of NO 3 — between root and shoot Ruiz and Romero, Our results show that higher 15 N distribution ratio in roots were found in K deficient or excess treatments, while the highest 15 N distribution ratio in leaves appeared under appropriate K supply treatments. This suggests that appropriate K supply not only increases NO 3 — absorption in roots, but also promotes the transport from roots to shoots.

Rufty et al. So it is necessary to focus on the effect of K on N assimilation in roots and leaves. The inhibition of K deficiency on NR activity has been verified in cotton, cucumber, and Arabidopsis Ruiz and Romero, ; Balkos et al. Consistent with previous results, we also found that for a certain range, with the increase of K supply, GS activity of roots and NR activity of leaves of M9T seedlings gradually increased, which promoted the assimilation of NO 3 —.

However, when the K supply is too high, the activity of these enzymes will decrease, which may be related to the inhibition of photosynthesis and the reduction of energy supply. The absorption and distribution of nitrate also depends on the energy and C skeleton from photosynthesis Liu et al. As the amount of fertilizer is increased, the amount of extra yield is reduced There comes a point where the value of the extra crop is less than the cost of the extra fertilizer.

Another reason to only apply the right amount of fertilizer and not too much. John Hewitson. Nitrate accumulation in vegetables and its residual in vegetable fields. Ikemoto Y. Plasma level of nitrate in congenital heart disease: Comparison with healthy children. Donner S. Evaluating the impacts of land management and climate variability on crop production and nitrate export across the Upper Mississippi Basin.

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Food Agr. Mensinga T. Health implications of exposure to environmental nitrogenous compounds. Gardner W. Water Content. In: Klute A. Thomas G. Soil pH and Soil Acidity. In: Sparks D. Rhoades J. Gee G. Particle-size Analysis. Nelson D. Sumner M. Cation Exchange Capacity and Exchange Coefficient. Bremner J. In: Page A. Juang C. Rationalization Application of Fertilizers in Vegetable Farmlands; pp. Testing Soils for Salinity and Sodicity. In: Westerman R. Soil Testing and Plant Analysis.

Soil Science Society of America Inc. Lee S. Application effect of food waste compost abundant in NaCl on the growth and cationic balance of rice plant in paddy soil. Lee J. Effect of food waste compost on microbial population, soil enzyme activity and lettuce growth. Chen B. Effects of nitrate supply on plant growth, nitrate accumulation, metabolic nitrate concentration and nitrate reductase activity in three leafy vegetables.

Plant Sci. Petropoulos S. The effect of nitrogen fertilization on plant growth and the nitrate content of leaves and roots of parsley in the Mediterranean region. Herencia J. Comparison of nutritional quality of the crops grown in an organic and conventional fertilized soil. Malmauret L. Those are divided into macronutrients, which plants need a lot of, and micronutrients, which plants need in trace amounts. The primary macronutrients are nitrogen N , phosphorus P , and potassium K.

Plants do absorb these nutrients from soil, but the soil can quickly become depleted of these major nutrients because the plants use large amounts.

Gardeners typically replace these nutrients through fertilizer. Bags of plant fertilizer are labeled with numbers such as , or other numbers. These numbers indicate the percentage of N, P and K is in each bag of fertilizer. N, P and K is crucial to a plant's growth, and each element controls and affects a different phase of plant growth. According to the Old Farmer's Almanac , nitrogen promotes leaf growth and the green color in plants.

Phosphorus promotes root development, which is important to help plants grow strong over time. Potassium, also listed on fertilizer bags as potash, helps the plant fight off disease and keeps it resilient to withstand things like temperature fluctuations.