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以霍格兰营养液为培养基质,采用~(15)N同位素示踪技术,研究不同浓度~(15)NO_3~--N(0、2.5、5、10和20 mmol·L~(-1),分别以N_0、N_1、N_2、N_3和N_4表示)对平邑甜茶幼苗生长、光合作用、~(15)N吸收、利用及分配的影响。结果表明:与其他处理相比,N_2处理的幼苗叶绿素含量、叶面积及各器官干质量最大。叶片净光合速率(Pn)随~(15)NO_3~--N浓度的增加显著增大,但~(15)NO_3~--N浓度超过N_2处理后Pn略有下降。处理20 d时,N_2处理的幼苗根系活力最大,根系长度、根系总表面积和根尖数也显著高于其他处理。各处理间~(15)N分配率差异显著,N_2处理下幼苗各器官间~(15)N分配率最均衡,~(15)N利用率也较高;随~(15)NO_3~--N浓度增加,各处理幼苗全氮量和~(15)N吸收量呈先升高后降低的趋势,且在N_2处理时最大,分别为103.77 mg和21.57 mg。处理12 d后,叶片硝酸还原酶(NR)活性以N_2处理最高,N_4处理最低,至第16天时,N_4处理较N_2处理降低了84.9%。因此,~(15)NO_3~--N供应过低抑制幼苗光合作用及氮素吸收,~(15)NO_3~--N供应过高则抑制幼苗体内硝态氮同化及根系生长,均不利于苹果幼苗生长及氮素营养吸收利用,适量供氮有利于苹果幼苗的生长、光合作用的提高及氮素的吸收、利用和分配。
Using Hoagland nutrient solution as culture medium, ~ (15) N isotope tracing technique was used to study the effects of different concentrations of NO_3 ~ - N (0,2.5,5,10 and 20 mmol·L -1 ), Respectively, N_0, N_1, N_2, N_3 and N_4) on the growth, photosynthesis, absorption and utilization of ~ (15) N and the distribution of The results showed that compared with other treatments, the content of chlorophyll, leaf area and dry weight of all organs of N 2 treatment were the highest. The net photosynthetic rate (Pn) of leaves increased significantly with the increase of ~ (15) NO_3 ~ - N concentration, but Pn slightly decreased after ~ (15) NO_3 ~ - N concentration exceeded N_2 treatment. When treated for 20 days, the root activity of N 2 -treated seedlings was the highest, and the length of root system, total surface area of root system and root tip number were also significantly higher than those of other treatments. The distribution rate of ~ (15) N in each treatment was significantly different. The distribution of ~ (15) N in all organs under N_2 treatment was the most balanced and the utilization rate of ~ (15) N was also higher. N concentration increased, the total nitrogen content and the uptake of 15 N in the seedlings increased firstly and then decreased, and reached the maximum at the N 2 treatment of 103.77 mg and 21.57 mg, respectively. Nitrate reductase (NR) activity of leaves was highest in N_2 treatment and lowest in N_4 treatment after 12 days of treatment. By the 16th day, N_4 treatment decreased 84.9% compared with N_2 treatment. Therefore, the supply of ~ (15) NO_3 ~ - N inhibited the photosynthesis and nitrogen absorption of seedlings, and the excessive supply of ~ (15) NO_3 ~ - N inhibited the nitrate nitrogen assimilation and root growth in seedlings, Apple seedling growth and nitrogen absorption and utilization of nutrients, adequate nitrogen supply is conducive to the growth of apple seedlings, photosynthesis and nitrogen uptake, utilization and distribution.