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
A field experiment was carried out in a six-year old 'Fuji3'/M26/Malus hupehensis Rehd. apple with 15N and 13C labeled tracers, to understand 13C assimilation capability and the characteristics of translocation and distribution of 13C-photosynthate and 15N to fruit under different nitrogen application levels (urea 0%, 0.6%, 1.2%, 1.8%, 2.4%, CK, N1, N2, N3, N4, respectively) to smear the leaves within 20 cm around the fruit at late stage of fruit enlargement. The results showed that, with the increases of urea application, the chlorophyll content, nitrogen content, net photosynthetic rate, sorbitol and sucrose content, sorbitol 6-phosphate dehydrogenase (S6PDH) and sucrose phosphate synthase (SPS) activities, 13C assimilation capability of leaves were first increased and then decreased, with the highest value in 1.8% urea smear treatment and the lowest value with the treatment of clear water. The 13C of self retention (self leaves and self branches) was the highest in clear water (81.6%) and the lowest in 1.8% urea smear treatment (63.5%). The 13C was mainly allocated to fruit, followed by unlabeled perennial branch, and the lowest in unlabeled leaves. With the increases of urea application, the 13C absorption of fruit was first increased and then decreased, with the highest value in 1.8% urea smear treatment (1.21 mg·g-1) and the lowest value in clear water (0.51 mg·g-1). The 15N absorption of fruit was enhanced with the increases of urea application. These results indicated that foliage application of urea solution improved translocation and distribution of leaf photosynthate and nitrogen to fruit with varying degrees, which was the highest in 1.8% urea smear treatment and could avoid excessive intake of nitrogen to fruit.
Subject(s)
Agriculture/methods , Carbon Radioisotopes/metabolism , Malus/physiology , Nitrogen/metabolism , Fertilizers , Fruit , Malus/growth & development , Malus/metabolism , Photosynthesis , Plant LeavesABSTRACT
To clarify the effects and underlying mechanism of ABA on sugar accumulation in apple fruits, 13C trace technique was used to examined the effects of different ABA levels (0, 50, 100 and 150 mg·L-1) and fluoridone (ABA biosynthesis inhibitor) on translocation of photosynthate to fruit during late stage of fruit rapid-swelling in five-year-old 'Yanfu3'/M26/Malus hupehensis Rehd. The results showed that the activities of related enzyme in sugar metabolism, the relative expression of sucrose transporter gene MdSUT1, MdSUT2.2 and sorbitol transporter gene MdSOT3 tended to increase first and then decrease with increasing ABA concentration, with a peak in 100 mg·L-1ABA treatment. Fluridone treatment significantly inhibited the enzymes activities of sugar metabolism and the relative expression of sugar transporters. The treatment of 100 mg·L-1ABA significantly reduced leaf 13C content, increased fruit 13C content and increased the transport rate of photosynthate from leaves to fruits compared with other treatments. Our results indicated that exogenous ABA enhanced sink strength of fruit and promoted the transportation of more photosynthate to fruits, which increased the soluble sugar content in fruits.
Subject(s)
Abscisic Acid/metabolism , Fruit/physiology , Malus , Carbohydrate Metabolism , Carbohydrates , Fruit/chemistry , Plant LeavesABSTRACT
Taking a six-year old 'Orin' apple tree plantation ('Orin'/SH6/ Malus micromalus Makino) as test material, the effects of common urea treatment (CU), bag-controlled release ferti-lizers treatment (BCRF) and controlled-release nitrogen fertilizer treatment (CRNF) on 15N-urea absorption, utilization, loss and accumulation dynamics of nitrogen content in 0-80 cm soil layer were investigated by 15N labeled tracer method. The results showed that compared with CU treatment, both CRNF and BCRF treatments increased the inorganic nitrogen content in soil at the late stage of apple growth, the leaf SPAD value, leaf nitrogen content, net photosynthetic rate and 15N derived from fertilizer (Ndff value) of different organs at fruit maturity stage, with CRNF showing stronger effects than BCRF. The amount of 15N residue in 0-40 cm soil layer showed a decreasing trend in different phenological stages. The amount of 15N residue was the highest in CRNF, followed by BCRF, and the lowest in CU, among which CRNF declined gently with 15N residue mainly concentrated in the 0-40 cm soil layer. 15N residue in 40-80 cm soil layer showed an increasing trend in different phenological stages, which was the highest in CU, followed by BCRF, and the lowest in CRNF, and that of CRNF increased gently. The 15N fertilizer utilization rate of CRNF was 32.6% at fruit maturity stage, which was 1.11 and 1.56 times as high as that of BCRF and CU, whereas its 15N loss rate was 21.6%, being obviously lower than BCRF (35.6%) and CU (59.6%). CRNF significantly improved fruit yield and quality and increased economic benefits.
Subject(s)
Fertilizers , Malus/chemistry , Nitrogen/analysis , Delayed-Action Preparations , Malus/growth & development , Nitrogen Isotopes/analysis , Soil , UreaABSTRACT
Three kinds of potted one-year-old pear rootstocks (Pyrus calleryana, P. pashia, and P. xerophila) and 15N trace technique were used to examine the effects of different phosphorus application rates (P0, P1, P2, P3 and P4 equivalent to 0, 50, 100, 150 and 200 kg·hm-2 P2O5, respectively) on plant growth and the characteristics of 15N-urea absorption and utilization. The results showed that, with the increases of phosphorus levels, plant height, ground diameter, dry mass, root surface area, root length, number of root tips, root activity, root respiration rate, Ndff values, and nitrogen use efficiency of rootstocks first increased and then decreased. However, the range of rise and fall of different rootstocks were distinct, and each index reached the highest level at different phosphorus levels. The plant height, diameter, dry mass of P. xerophila were the highest under the same phosphorus level, followed by P. pashia, and P. calleryana was the lowest. The root architecture parameters and root respiration rate showed the same trend, but Ndff values and nitrogen use efficiency performed different. Under different phosphorus levels, each index of P. xerophila reached the highest level at P3, but those of P. pashia and P. calleryana appeared at P2 and P1 rates, respectively. The Ndff values in stem were the highest among different organs of rootstocks at diffe-rent phosphorus levels, and the highest nitrogen use efficiency of P. xerophila, P. pashia and P. calleryana was 9.6%, 8.9% and 8.3%, respectively. The variations of plant growth and N absorption and utilization of different pear rootstocks across different phosphorus levels indicated that phosphorus fertilizer should be carry out reasonably in practice and give full consideration of phosphorus demands of plants.