不同供钾水平对平邑甜茶幼苗生长及NO3-吸收利用特性的影响

研究平邑甜茶幼苗NO₃^--N吸收和利用特性对不同供钾水平的响应,旨在明确钾肥对氮肥吸收利用的影响,从而为果园科学施肥提供理论依据.以平邑甜茶幼苗为材料进行砂培试验,设置K₀、K₁、K₂、K₃、K₄、K₅、K₆ 7个钾浓度处理,分别相当于0、2、4、6、8、10、12 mmol·L^-1 K⁺,运用¹⁵N同位素示踪技术和非损伤扫描离子选择电极技术,测定了不同供钾水平下平邑甜茶的氮素吸收和利用情况.结果表明: K₃处理平邑甜茶幼苗根系活力、硝酸还原酶活性以及根系形态指标均显著高于其他处理.与其他处理相比,K₃处理根、茎、叶从肥料中吸收分配到的¹⁵N 量对该器官全氮量的贡献率(Ndff)均达到最高,分别为K₀处理的1.36、1.33和1.47倍.随供钾水平的增加,植株氮素利用率呈现先增高后降低的趋势,且在K₃处理时最大,为23.3%,是K₀处理的3.04倍.非损伤微测技术结果显示,K₃处理时,平邑甜茶根系对NO₃^-有强烈吸收且内流速度达到最大,为19.34 pmol·cm^-2·s^-1;在缺钾(K₀)和高钾(K₆)处理时有明显外排趋势.因此,钾的亏缺或过量均抑制氮素的吸收和利用,适当供钾能够促进幼苗根系生长,增强硝酸还原酶活性,从而促进平邑甜茶对氮素的吸收.

Effects of different potassium levels on growth and NO3- uptake and utilization of Malus hupehensis seedlings

In order to explore the effects of potassium fertilizer on the absorption and utilization of nitrogen fertilizer, and provide theoretical basis for scientific fertilization in apple orchard, Malus hupehensis seedlings were used to study the effects of different potassium levels (K₀, K₁, K₂, K₃, K₄, K₅, and K₆ equivalent to 0, 2, 4, 6, 8, 10, and 12 mmol·L^-1 K⁺, respectively) on growth and NO₃^- uptake and utilization using the track technology of ¹⁵N and non-damage microtest technique. The results showed that root vigor, nitrate reductase activity and root morphological index of seedlings in K₃ treatment were significantly higher than those in the other treatments. The ¹⁵N derived from fertilizer (Ndff) in different organs of M. hupehensis seedlings was significantly different among treatments, and the Ndff values of root, stem and leaf appeared in K₃ treatment were the highest, being 1.36, 1.33 and 1.47 times as those of the K₀ treatment, respectively. With the increase of potassium application rate, the ¹⁵N utilization rate of seedlings were firstly increased and then decreased, and reached the highest value (23.3%) in K₃ treatment, which was 3.04 times as that of K₀ treatment. The results of non-damage microtest technique showed that there was a strong absorption of NO₃^- in K₃ treatment (19.34 pmol·cm^-2·s^-1), while a clear trend of outflow was observed in the potassium deficiency (K₀) and high potassium (K₆) treatments. Therefore, the deficit or excess of potassium could inhibit the uptake and utilization of nitrogen, while appropriate potassium could promote root growth, enhance the activity of nitrate reductase, and then increase the absorption of nitrogen by seedlings.