| Under the natural conditions, the growth of citrus rootstocks mainly depends on the mycorrhiza which formed in plant roots.Since there is no mycorrhizal roots in the soilless culture, how to create a conducive environment for the rootstocks to grow becomes the focus of attention of many scholars.Besides,it's not convenient for us to observe the root morphology of the rootstocks which are planted in the soil, hydroponics can be used without harm to see the shape changes of the root visually and clearly.Nutrient deficiency environment can be formed rapidly by changing the nutrient solution formula appropriately.Researches for the growth of citrus under the nutrient deficiency conditions are universal,but for the morphology are few. So,we investigate physiological and biochemistry index of the citrus aurtantium seedlings growing in the nutrient solution with different dissolved oxygen concentrations,in order to find out the effect caused by the dissolved oxygen to the growth of citrus aurtantium.We also investigate the root morphology index of the seedlings under the nitrogen-deficiency and iron-deficiency nutrient solution. The main results show that:1 Optimization of a hydroponic culture system for citrus(1)Effect of different dissolved oxygen concentrations on growth of the seedlingsCompared to the citrus seedlings with no air aeration to the nutrient solution(control), the height of the plants of the different aeration treatments increases by the time,and the height of T1 increases considerably in the late period.The growth of leaf area of the plants with different aeration treatments enhances slowly in the first 8 weeks,from the 8th to 12th week it enhances significantly.The leaf area of T1 has significant increase during the experiment,from 4.395cm2 to 60.383 cm2.The fresh and dry weight of the plants with different aeration treatments increases slowly in the previous period, the seedlings grow faster and the accumulation of dry matter was significantly increases in the late period(2)Effect of different dissolved oxygen concentrations on physiological and biochemistry indexCompared to control,relative electronical conductivity of the treatments with different aeration is significantly lower,Tland T2 have a lesser extent in the relative electronical conductivity,but the values of T3 and T4 are higher.Content of MDA increases gradually from T1 to T4,because of the decrease frequency of aeration,as a result,oxygen can inhibit the production of MDA and increase the vigor of the plant eith anti-aging.Values of the root activity of the different aeration treatments are all higher than CK dealed with the same number of days.The values of the root activity of T1 and T2 have no significant defference.Content of soluble protein basically has no change in Tl,changes of T2 to T4 are also not significant,they all in a certain range.The peak of soluble sugar content in T1,T2,T3 all appear 8 weeks after treatment,with an increase of 42.65%,61.10% and 70.61% compared with it before the treatment respectively.Tl maintains high levels of photosynthetic pigment content between the different aeration treatments. The maximum values of Chlorophyll a, total chlorophyll and carotenoid content in T1 appear 8 weeks after treatment, the photosynthetic pigment content of T2,T3,T4 changed little, fluctuating within a certain range.2 Study on root morphology response to nitrogen-deficiency and iron-deficiency of Poncirus seedlings(1)Effect of nitrogen-deficiency and iron-deficiency on growth of the seedlingsCompared to the citrus seedlings growing in the full nutrient solution(control),height of the nitrogen-deficiency and iron-deficiency plant is only 16.4cm and 27.6cm,while the height of control is 44.0cm. Plant leaf area of control were significantly higher than those of nitrogen deficiency and iron-deficiency plant.Dry matter accumulation of nitrogen-deficiency plants are significantly lower than control,the biomass of iron-deficiency plant is between the control and nitrogen treatments.(2) Effect of nitrogen-deficiency and iron-deficiency on root morphology of the seedlingsMain root diameter of nitrogen-deficiency and iron-deficiency plants decrease slightly,there is no difference of lateral root average diameter in all treatments and control, nitrogen-deficiency plant has significantly larger root volume.Main root length and total root length of nitrogen-deficiency plants increases with significantly reduced the number of lateral roots. iron-deficiency plant has the largest main root length,but the total root length was inhubited and the number of its lateral roots reduced significantly.Root activity of nitrogen-deficiency and iron-deficiency plants decreases significantly, nitrogen-deficiency plants have the larger root surface area than control,but decline has been observed in iron-deficiency plants.(3)Effect of nitrogen-deficiency and iron-deficiency on nutrient content of the seedlingsContent of N and P of nitrogen-deficiency plants is all lower in roots,stems and leaves.Only the content of N of iron-deficiency plants in root is less than control, K concentrations of nitrogen-deficiency and iron-deficiency plants in root are significantly lower than control,with little difference in stems and leaves.Content of Fe of iron-deficiency plants in root is significantly lower than that of control and nitrogen treatment,but little difference is observed in stems and leaves.Content of Ca and Mg does not change in all treatments and control,indicating that there is little effect on absorption of Ca and Mg in those both nutrient deficiency. |
