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Root aeration improves growth and nitrogen accumulation in rice seedlings under low nitrogen.

ABSTRACT: In wetland soils, changes in oxygen (O2) level in the rhizosphere are believed to influence the behaviour of nutrients and their usage by plants. However, the effect of aeration on nitrogen (N) acquisition under different N supply conditions remains largely unknown. In this study, the rice cultivars Yangdao 6 (YD6, with higher root aerenchyma abundance) and Nongken 57 (NK57, with lower root aerenchyma abundance) were used to evaluate the effects of aeration on rice growth and N accumulation. Our results showed that the number of adventitious roots and the root surface area increased significantly, and ethylene production and aerenchyma formation decreased in both cultivars after external aeration (EA). Five N treatments, including no N (-N), 0.125 mM NH4NO3 (LN), 1.25 mM Ca(NO3)2 (NO3-N), 1.25 mM (NH4)2SO4 (NH4-N) and 1.25 mM NH4NO3 (N/N), were applied to YD6 and NK57 for 2 days under internal aeration or EA conditions. External aeration increased the root biomass in both cultivars and the shoot biomass in NK57 by 18-50 %. The total N concentrations in roots of YD6 grown under -N and LN and of NK57 grown under NO3-N were increased by EA. Expression of OsPAD4, one of four putative genes regulating aerenchyma formation, showed a similar pattern alongside changes in the ethylene level in the EA-treated rice irrespective of the N treatments. Furthermore, expression of the high-affinity nitrate transporter gene OsNRT2.1 was increased by EA under -N, LN and NO3-N conditions. Our data provide evidence of an interaction between O2 and the supply of N in ethylene production, aerenchyma formation and N nutrition through modification of the expression of OsPAD4 and OsNRT2.1.

SUBMITTER: Zhu J

PROVIDER: S-EPMC4685170 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature

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Root aeration improves growth and nitrogen accumulation in rice seedlings under low nitrogen.

Zhu Jingwen J Liang Jing J Xu Zhihui Z Fan Xiaorong X Zhou Quansuo Q Shen Qirong Q Xu Guohua G

AoB PLANTS 20151116

In wetland soils, changes in oxygen (O2) level in the rhizosphere are believed to influence the behaviour of nutrients and their usage by plants. However, the effect of aeration on nitrogen (N) acquisition under different N supply conditions remains largely unknown. In this study, the rice cultivars Yangdao 6 (YD6, with higher root aerenchyma abundance) and Nongken 57 (NK57, with lower root aerenchyma abundance) were used to evaluate the effects of aeration on rice growth and N accumulation. Our ...[more]

PMID: 26578743

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Project description:Low temperature and overcast rain are harmful to directly seeding early rice, it can hinder rice growth and lower rice biomass during the seedling stage, which in turn lowers rice yield. Farmers usually use N to help rice recuperate after stress and minimize losses. However, the effect of N application on the growth recovery for rice seedlings after such low temperature stress and its associated physiological changes remain unclearly. Two temperature settings and four post-stress N application levels were used in a bucket experiment to compare B116 (strong growth recovery after stress) with B144 (weak growth recovery). The results showed that the stress (average daily temperature at 12°C for 4 days) inhibited the growth of rice seedlings. Compared to the zero N group, the N application group's seedling height, fresh weight and dry weight significantly increased after 12 days. In particular, the increases in all three growth indicators were relatively higher than that of N application at normal temperature, indicating the importance of N application to rice seedlings after low temperature stress. The antioxidant enzyme activity of rice seedlings increased significantly after N application, which reduced the damaging effect of ROS (reactive oxygen species) to rice seedlings. At the same time, the soluble protein content of seedlings showed a slow decrease, while the H2O2 and MDA (malondialdehyde) content decreased significantly. Nitrogen could also promote nitrogen uptake and utilization by increasing the expression of genes related to NH4+ and NO3- uptake and transport, as well as improving the activity of NR (nitrate reductase) and GS (glutamine synthetase) in rice. N could affect GA3 (gibberellin A3) and ABA (abscisic acid) levels by regulating the anabolism of GA3 and ABA. The N application group maintained high ABA levels as well as low GA3 levels from day 0 to day 6, and high GA3 levels as well as low ABA levels from day 6 to day 12. The two rice varieties showed obvious characteristics of accelerated growth recovery and positive physiological changes by nitrogen application after stress, while B116 generally showed more obvious growth recovery and stronger growth-related physiological reaction than that of B144. The N application of 40 kg hm-2 was more conducive to the rapid recovery of rice growth after stress. The above results indicated that appropriate N application promoted rice seedling growth recovery after low temperature stress mainly by increasing the activities of antioxidant enzymes and nitrogen metabolizing enzymes as well as regulating the levels of GA3 and ABA. The results of this study will provide a reference for the regulation of N on the recovery of rice seedling growth after low temperature and weak light stress.

Project description:Background and aimsDomesticated maize (Zea mays ssp. mays) generally forms between two and six seminal roots, while its wild ancestor, Mexican annual teosinte (Zea mays ssp. parviglumis), typically lacks seminal roots. Maize also produces larger seeds than teosinte, and it generally has higher growth rates as a seedling. Maize was originally domesticated in the tropical soils of southern Mexico, but it was later brought to the Mexican highlands before spreading to other parts of the continent, where it experienced different soil resource constraints. The aims of this study were to understand the impacts of increased seminal root number on seedling nitrogen and phosphorus acquisition and to model how differences in maize and teosinte phenotypes might have contributed to increased seminal root number in domesticated maize.MethodsSeedling root system architectural models of a teosinte accession and a maize landrace were constructed by parameterizing the functional-structural plant model OpenSimRoot using plants grown in mesocosms. Seedling growth was simulated in a low-phosphorus environment, multiple low-nitrogen environments, and at variable planting densities. Models were also constructed to combine individual components of the maize and teosinte phenotypes.Key resultsSeminal roots contributed ~35 % of the nitrogen and phosphorus acquired by maize landrace seedlings in the first 25 d after planting. Increased seminal root number improved plant nitrogen acquisition under low-nitrogen environments with varying precipitation patterns, fertilization rates, soil textures and planting densities. Models suggested that the optimal number of seminal roots for nutrient acquisition in teosinte is constrained by its limited seed carbohydrate reserves.ConclusionsSeminal roots can improve the acquisition of both nitrogen and phosphorus in maize seedlings, and the increase in seed size associated with maize domestication may have facilitated increased seminal root number.

Project description:BACKGROUND:The trehalose (Tre) pathway has strong effects on growth and development in plants through regulation of carbon metabolism. Altering either Tre or trehalose 6-phosphate (T6P) can improve growth and productivity of plants as observed under different water availability. As yet, there are no reports of the effects of modification of Tre orT6P on plant performance under limiting nutrition. RESULTS:Here we report that nitrogen (N) metabolism is positively affected by exogenous application of Tre in nitrogen-deficient growing conditions. Spraying foliage of tobacco (Nicotiana tabacum) with trehalose partially alleviated symptoms of nitrogen deficiency through upregulation of nitrate and ammonia assimilation and increasing activities of nitrate reductase (NR), glycolate oxidase (GO), glutamine synthetase (GS) and glutamine oxoglutarate aminotransferase (GOGAT) with concomitant changes in ammonium (NH4+) and nitrate (NO3-) concentrations, glutamine and amino acids. Chlorophyll and total nitrogen content of leaves and rates of photosynthesis were increased compared to nitrogen-deficient plants without applied Tre. Total plant biomass accumulation was also higher in Tre -fed nitrogen-deficient plants, with a smaller proportion of dry weight partitioned to roots, compared to nitrogen-deficient plants without applied Tre. Consistent with higher nitrogen assimilation and growth, Tre application reduced foliar starch. Minimal effects of Tre feeding were observed on nitrogen-sufficient plants. CONCLUSIONS:The data show, for the first time, significant stimulatory effects of exogenous Tre on nitrogen metabolism and growth in plants growing under deficient nitrogen. Under such adverse conditions metabolism is regulated for survival rather than productivity. Application of Tre can alter this regulation towards maintenance of productive functions under low nitrogen. This has implications for considering approaches to modifying the Tre pathway for to improve crop nitrogen-use efficiency and production.

Dataset Information

Root aeration improves growth and nitrogen accumulation in rice seedlings under low nitrogen.

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Root aeration improves growth and nitrogen accumulation in rice seedlings under low nitrogen.

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