两种供钾水平下不同铵硝比对烟株幼苗生长和钾吸收的影响

Effects of Different Ammonium/Nitrate Ratios on Seedling Growth and Potassium Uptake of Tobacco Plants under Two Potassium Supply Conditions

为探明有利于烤烟生长和钾素吸收的铵硝配比,以豫烟6号为材料,水培条件下研究了2种供钾浓度下(1.5、5.0mmol/L)不同铵硝配比对烟株根系生理生长、叶片光合特征、烟株钾含量和吸收动力学的影响。结果表明,(1)低钾抑制烟草幼苗根系生长。两个钾水平下,随着铵硝配比下降,根干质量、根系构型和生理特征等指标数值呈先增后降,在铵硝配比为25/75时含量最高。(2)适当铵硝配比可提高两个钾水平下烟株叶片光合效率。低钾条件下随铵硝配比的下降,烟草叶片的叶绿素含量及光合效率呈先上升后下降的趋势,当铵硝配比为25/75时净光合速率比纯铵态氮和纯硝态氮处理显著提高152.35%和56.08%。(3)随着铵硝配比降低,烟株钾素含量和钾吸收动力学Vmax值升高,正常钾水平下铵硝配比为25/75时钾素含量及Vmax最高,低钾水平下烟株钾含量随着铵硝配比降低而持续增加。综上,降低铵硝比例可改变烟株根系构型和促进根系生长,提高植株钾素含量,缓解钾缺乏对烟株生长和钾吸收的抑制作用,以铵硝配比为25/75时烟株幼苗综合性状最优。

In order to find out the appropriate ratio of ammonium/nitrate for plant growth and potassium absorption of flue-cured tobacco,the effects of different ratios of ammonium/nitrate on physiological growth of root,leaf photosynthesis,potassium content and absorption kinetics of tobacco plants at two potassium supply conditions were studied under hydroponic conditions with Yuyan No.6 as the material.The results showed that(1)Low potassium inhibited root physiological growth of tobacco seedlings.Root dry weight,root configuration indexes and physiological characteristics of tobacco seedlings increased first and then decreased with the decrease of ammonium/nitrate ratio at both potassium levels,and the highest content was found when the ammonium/nitrate ratio was 25/75.(2)The photosynthetic efficiency of tobacco plants under two potassium levels could be improved at an appropriate ratio of ammonium/nitrate.Under low potassium level,the chlorophyll content and photosynthetic efficiency of tobacco leaves increased first and then decreased with the decrease of ammonium/nitrate ratio.When the ammonium/nitrate ratio was 25/75,the net photosynthetic rate of tobacco leaves was significantly increased by 152.35%and 56.08%compared with that of pure ammonium and pure nitrate treatments.(3)With the decrease of ammonium and nitrate ratio,the potassium content and potassium absorption kinetics Vmax values increased.The potassium content and Vmax were the highest when the ammonium/nitrate ratio was 25/75 at the normal potassium supply level.Under low potassium level,the potassium content in tobacco plants continued to increase with the increase of nitrate/ammonium ratio.Therefore,reducing ammonium/nitrate ratio could change root architecture,promote root growth,and increase plant potassium content of tobacco plants.Meanwhile the inhibition effect of potassium deficiency on the growth and potassium absorption of tobacco plants could be alleviated.When the ammonium/nitrate ratio was 25/75,the comprehensive character of the tobacco plants was optimal.