光照强度减弱对刺梨吸收硝态氮和铵态氮的影响

Effect of Reduced Light Intensity on Nitrate and Ammonium Uptake of Rosa roxburghii Seedlings

探究光照强度减弱对刺梨(Rosa roxburghii Tratt.)实生苗根系的氮素吸收及相关生理特性的影响,为刺梨栽培的氮素营养调控提供科学依据。以‘贵农5号’刺梨品种实生苗为材料,以自然光照强度为对照(R0,CK),采用遮光的方法,在自然光照强度下和光照强度减弱20%(R20%)、40%(R40%)、60%(R60%)的条件下对刺梨苗进行培养,30 d后测定植株的氮含量。采用离子耗竭法,对不同光照强度下分别供给硝态氮和铵态氮的刺梨苗根系吸收NO_(3)^(-)和NH_(4)^(+)的动力学参数进行测定,并同时测定叶和根中的硝酸还原酶(NR)和谷氨酰胺合成酶(GS)的活性和植株中的碳水化合物含量,分析NO_(3)^(-)和NH+4吸收的动力学参数与叶、根中NR、GS活性的相关性。结果表明,在不同光照强度下,刺梨苗根系对NO_(3)^(-)和NH_(4)^(+)的吸收规律均可用Michaelis-Menten动力学方程进行描述。不同光照强度下的刺梨苗根系对NO_(3)^(-)的最大吸收速率(I_(max))、亲和力表征的参数Km和NO_(3)^(-)流入根系的速率参数α都始终比NH_(4)^(+)的大。随光照强度的减弱,分配到根中的可溶性糖和淀粉减少,根系对NO_(3)^(-)和NH+4的Imax值和α值不断降低,叶和根中的NR、GS活性也随之减弱。刺梨苗根系吸收NO_(3)^(-)和NH_(4)^(+)的I_(max)值、α值与叶、根中NR和GS的活性呈极显著正相关,Km与叶、根中的NR和GS活性的相关性不明显。光照强度减弱会严重降低刺梨苗中的氮含量,无论供给硝态氮或铵态氮,光照强度减弱都没有改变刺梨偏好吸收硝态氮的特性,但当光照强度减弱的程度达到比自然光照强度低20%的条件下,会严重抑制刺梨根系对NO_(3)^(-)和NH_(4)^(+)的吸收。生产中可通过改善光照条件促进刺梨对氮的吸收。

Exploring the effect of reduced light intensity on nitrogen absorption and related physiological characteristics of Rosa roxburghii Tratt. seedling root, this research provides a scientific basis for nitrogen nutrition regulation in the cultivation of Rosa roxburghii. In this experiment, the seedlings of ‘Guinong 5’ were used as the material, the natural light intensity was used as the control(R0 CK), and the method of light-blocking was applied. The Rosa roxburghii seedlings were cultivated under natural light intensity and light intensity of only 20%(R20%), 40%(R40%), 60%(R60%) of natural light intensity, then the nitrogen content in the Rosa roxburghii seedlings were determined after 30d of cultivation. Using the method of ion-depletion, the kinetic parameters of the absorption of NO_(3)^(-)and NH_(4)^(+) in the roots of Rosa roxburghii seedlings were determined under different light intensities supplied with nitrate and ammonium nitrogen, and meanwhile the activity of NR and GS in leaves and roots, the carbohydrate content in the Rosa roxburghii seedlings were determined, then the correlation of absorption kinetic parameters of NO-3and NH+4with the NR and GS activity in leaves and roots was also analyzed. The results showed that the absorption rules of NO-3and NH+4of Rosa roxburghii seedlings root could be described by the Michaelis-Menten kinetic equation under different light intensities. Under different light intensities, the maximum absorption rate(Imax), parameters of the affinity characterization(Km) and rate parameters of NO_(3)^(-)inflow into root(α) were always greater than that of NH_(4)^(+). As the light intensity decreased, soluble sugars and starch allocated to the roots were reduced, the Imaxand α of NO_(3)^(-)and NH_(4)^(+)in roots were reduced, and the NR and GS activities in the leaves and roots were also diminished. The Imaxand α of NO_(3)^(-)and NH_(4)^(+)absorbed by Rosa roxburghii seedlings roots were extremely significantly positive correlated with the activity of NR and GS in leaves and roots, while the correlation between Kmand NR and GS activity in leaves and roots was not apparent. The weakened light intensity seriously reduced the nitrogen content of Rosa roxburghii seedlings. Whether supplied with nitrate or ammonium nitrogen, the preference of Rosa roxburghii to absorb nitrate was not changed with light intensity reduction. However, when the light intensity was weakened to less than 20% of the natural light intensity, the absorption of NO_(3)^(-)and NH_(4)^(+)in the root would be severely inhibited. Therefore, improving light conditions can promote nitrogen absorption of Rosa roxburghii in production.