Effects of localized high nitrate supply on maize roots morphology and N accumulation
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DOI:10.7606/j.issn.1000-7601.2019.04.12
Key Words: maize  primary root  seminal root  nitrate supply  water stress
Author NameAffiliation
ZHAI Xiao-fang College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, Yangling, Shaanxi 712100, China 
ZHOU Jun-xi College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, Yangling, Shaanxi 712100, China 
SUN Hao-ran College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China 
TANG Liang College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, Yangling, Shaanxi 712100, China 
SHEN Yu-fang State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, Yangling, Shaanxi 712100, China 
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Abstract:
      The root system development displays a high plasticity to heterogeneous distribution of N in soil. Nitrate is the most common N source used by higher plants in arid environment. How maize roots coordinate the growth of primary roots (PR) and seminal roots (SR) in response to heterogeneous localized high nitrate supply remains unclear. Maize seedlings, Zhengdan 958 and Ludan 981, were grown in split-root systems for three weeks by hydroponic culture. The roots received a uniform low nitrate supply of 0.5 mM nitrate (LPR-LSR), or a high nitrate supply of 5 mM nitrate for primary roots and low for seminal roots (HPR-LSR), or low nitrate supply for primary roots and high for seminal roots (LPR-HSR) under the normal water supply and water stress environment. Morphology, biomass, and N accumulation in roots were measured. The results showed that Zhengdan 958 had greater root length and surface area of primary roots, root biomass, shoot biomass, and N accumulation than Ludan 981. The length, surface area, volume of primary roots, shoot biomass and N accumulation were lower under water stress treatment than that of normal water treatment. Maize primary roots and seminal roots responded differently to local high nitrate supply. Localized high nitrate treatments could promote the growth of primary and seminal roots, especially root length and surface area, under the normal water supply. Under the normal water condition, the increment of root length and surface area of primary roots ranged from 6.8% to 27.3% and 1.9% to 21.9%, respectively; except the Zhengdan 958 under the HPR-LSR treatment, the increment of root length and surface area of seminal roots ranged from 30.4% to 92.7% and 10.5% to 135.1%, respectively. However, under the water stress condition, the increment of root length and surface area of primary roots ranged from 24.6% to 152.9% and 62.1% to 229.9%, respectively, but the reduction of length of seminal roots randge from 10.0% to 29.9%, suggesting that water stress could affect the response of seminal roots to localized high nitrate supply. Localized high nitrate treatments increased the biomass and N accumulation of roots in both sides at the same time except for the LPR-HSR treatment under the water stress condition. Localized high nitrate could enhance the biomass and N accumulation of shoot both under the normal water supply and water stress environment compared with LPR-LSR treatment, under the LPR-HSR treatment, the increment ranged from 35.0% to 107.9% and 162.9% to 291.1% respectively, under the HPR-LSR treatment, the increment ranged from 56.7% to 109.4% and 204.1% to 377.0%, respectively. And the increment of HPR-LSR treatment was higher than LPR-HSR treatment. It indicated that the enhancement effects were more significant when the primary root was in the localized high nitrate supply.
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