ABSTRACT
A field experiment was carried out in a six-year old 'Fuji'3/M26/Malus hupehensis Rehd. apple with the 13C tracer method to examine the changes of chlorophyll fluorescence parameters, photosynthetic characteristics of leaf, sugar transporter gene expression, 13C assimilation capability and the characteristics of translocation and distribution of 13C-photoassimilates to fruit under different levels of potassium addition (K2O 0, 0.5%, 1.0%, 1.5%, 2.0%, expressed by CK, K1, K2, K3, K4, respectively). Potassium aqueous solution smear the leaves within 20 cm around the fruit at fruit enlargement stage. Compared with other treatments, K3 treatment significantly increased Rubisco enzyme activity, net photosynthetic rate, maximal photochemical efficiency of PSII, actual photochemical efficiency of PSII, coefficient of photochemical quenching, sorbitol and sucrose content, sorbitol 6-phosphate dehydrogenase (S6PDH) and sucrose phosphate synthase (SPS) enzyme activities and 13C assimilation capability of leaves. Furthermore, K3 treatment increased gene expression of sorbitol transporter MdSOT1 and MdSOT2 and sucrose transporter MdSUT4, and promoted the unloading of sugar in fruit. The 13C of self retention (self leaves and self branches) was the highest in CK (82.6%) and the lowest in K3 treatment (60.5%). With increasing potassium concentration, the 13C absorption of fruit first increased and then decreased, which was the highest in K3 treatment (1.31 mg·g-1) and the lowest in CK (0.57 mg·g-1). Our results indicated that foliage application of potassium solution improved PSII photochemical efficiency, activities of key enzymes related with carbon assimilation, synthesis ability, and outward transport ability of photosynthates in leaves, and consequently promoted the directional transportation of sugar to fruit. The amount of photoassimilates transported to fruit was the most under 1.5% K2O treatment (K3).
Subject(s)
Malus , Fruit , Photosynthesis , Plant Leaves , PotassiumABSTRACT
We examined nitrogen use efficiency of 15N-urea of 15-year-old 'Gala' apple trees by broadcast fertilization (T1), nitrogen fertilization with drip irrigation (T2) and nitrogen fertilization with subsurface irrigation (T3), to further improve the water and fertilizer integration technology for apple orchard and to improve nitrogen utilization efficiency. The results showed that leaf area, chlorophyll, and leaf nitrogen content of leaves were significantly higher in T3 treatment than those in T1 and T2 treatments. Soil mineral nitrogen content (20-40 cm) in each period followed the order of T3>T2>T1, while that in 0-20 cm followed an order of T2>T3>T1. The Ndff value at organ level (the contribution rate of the 15N amount absorbed by various organs of the tree to the total nitrogen content of the organ) was the highest in T3 treatment in each period, followed by T2 and T1 treatments. The utilization rate of 15N in the fruit ripening period followed an order of T3>T2>T1. The 15N utilization rate of T3 reached 24.2%, being 1.19 and 1.65 times of T2 and T1, respectively. The 15N distribution rate in the fruits during the fruit maturity stage was the highest in T1 treatment, while that in the storage organs was the highest in T2 treatment and that in the reproduction organs was the highest in T3 treatment. The single fruit weight, yield, soluble solids, hardness, soluble sugar and sugar-acid ratio were the highest in T3 treatment, followed by T2 and T1 treatments. In summary, nitrogen application by percolation irrigation (subsurface application) significantly promoted leaf growth and nitrogen utilization of apple tree, and improved fruit yield and quality.
Subject(s)
Malus , Fertilizers , Fruit , Nitrogen , Soil , WaterABSTRACT
15N trace technique was used to explore the characteristics of 15N-urea absorption, utilization, loss and fruit quality of eight-year-old 'Yanfu3'/M26/Malus hupehensis Rehd. seedlings. There were three different nitrogen fertilization treatments: one-time nitrogen application in spring (1), two times nitrogen application (2), the intensive technique of nitrogen application with several times application and reduction in amount (3). The results showed that leaf area, chlorophyll content (SPAD value), photosynthetic rate (Pn), total N content of leaves and the total biomass per plant (except fruit), as well as the root-shoot ratio of treatment 3 were obviously higher than those in the treatments of 1 and 2. Treatment 3 significantly increased the protective enzymes (SOD, POD and CAT) activities and decreased the malondialdehyde (MDA) content in leaves. Significant differences were found on the 15N derived from fertilizer (Ndff value) of different organs, with the fruit Ndff showing the highest, followed by the one-year-old branches, leaves and roots of the three treatments. The Ndff values of each organ were the highest in the treatment 3. At fruit maturity stage, total N content of plant in treatment 3 was 93.0 mg·kg-1, which was obviously higher than that in the treatments 1 (70.2 mg·kg-1) and 2 (81.9 mg·kg-1). 15N nitrogen utilization ratio of treatment 3 was 33.6%, which was obviously higher than that in the treatments 1 (20.4%) and 2 (26.0%). The 15N loss rate was 46.9% in treatment 3, being obviously lower than that in the treatments 1 (56.5%) and 2 (52.9%). There were significant differences of fruit mass, soluble solid, fruit firmness, soluble sugar content, titratable acids and sugar-acid ratio among different treatments, with the highest values in the treatment 3 and the lowest values in treatment 1.
Subject(s)
Fertilizers , Malus/growth & development , Nitrogen , Fruit , Plant Leaves , TreesABSTRACT
Two-year-old potted Fuji 3 apple trees on different rootstocks [Fuji 3/M. micromalus Makin (joe), Fuji 3/M7 (semi-dwarf) and Fuji 3/M26/M. micromalus Makin (dwarf)] were used to study leaf morphology and photosynthesis and the characteristics of distribution and utilization of 13C and 15N at different nitrogen supply levels (0N, 25%N and 100%N, the N content in 100% N treatment was the same as that in Hoagland complete nutrient solution) under sand culture condition. The main results were as follows: At shoot growth cessation stage in autumn, the leaf chlorophyll content (SPAD), leaf nitrogen content and photosynthetic rate were found the highest in Fuji 3/M. micromalus Makin, followed by Fuji 3/M7, and the lowest was found in Fuji 3/M26/M. micromalus Makin under the same nitrogen stress treatments (0N and 25%N), however, under normal nitrogen treatment (100%N) Fuji 3/M26/M. micromalus Makin had the highest leaf SPAD value, photosynthetic rate and the nitrogen content, followed by Fuji 3/M7, and the lowest was found in Fuji 3/M. micromalus Makin. The leaf SOD and CAT activities showed Fuji 3/M. micromalus Makin > Fuji 3/M7 > Fuji 3/M26/M. micromalus Makin under the same nitrogen stress treatments, but showed Fuji 3/M26/M. micromalus Makin > Fuji 3/M7 > Fuji 3/M. micromalus Makin under the normal nitrogen treatment. There were significant differences in the distributions of 15N and 13C in root and leaf in the 3 scion-stock combinations, and the distribution rates of 15N and 13C in roots were the highest under nitrogen stress treatments and in the order of Fuji 3/M. micromalus Makin > Fuji 3/M7 > Fuji 3/M26/M. micromalus Makin. The distribution rates of 15N and 13C in leaves were the highest under the normal nitrogen treatment and in the order of Fuji 3/M26/M. micromalus Makin > Fuji 3/M7 > Fuji 3/M. micromalus Makin. The 15N utilization ratio differed significantly among the 3 scion-stock combinations under different nitrogen application levels and was in the order of Fuji 3/M. micromalus Makin (44.3%, 37.5% and 31.4%)> Fuji 3/M7 (38.8%,30.7% and 26.6%) > Fuji 3/M26/M. micromalus Makin (32.0%,27.2% and 22.5%).
