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Anatomical features in avocado root and shoot vascular tissue. A) Root section from a plant in the H 2 O 2 soil injection treatment (100X). B) Spring shoot section from a plant in the H 2 O 2 soil injection treatment (40X). “X” indicates xylem tissue; “P” indicates phloem tissue.
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Commercial avocado production in Chile has expanded to areas with poorly drained soils presenting low oxygenation over significant periods of time throughout the year. In many of these areas, irrigation management is difficult because plantations are often placed on slopes of hills. Poorly aerated soils combined with irrigation design and managemen...
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... in either O 2 and CO 2 composition or ODR, during a day with several irrigation pulses. It may therefore be presumed that changes would be momentary and that those specific changes in the concentration of O 2 in the soil could generate a better root oxygenation and thus ATP production. The xylem/phloem ratio in roots and shoots, the number and mean area of root xylem vessels, and the total root xylem areas are shown in Table 5. An example of the anatomical features of xylem vessels in roots and spring shoots is shown in Figure 1. Although for almost all histological variables measured the roots and shoots of treated plants had a larger xylem system, the differences were only statistically significant for the spring shoot xylem/phloem ratio (P ≤ 0.15). Histological examination of avocado roots revealed larger xylem mean vessel diameters for plants in the H 2 O 2 injection treatment than those in the control treatment, indicating that H 2 O 2 soil injection leads to root anatomy improvement in avocado more than growth of the root system. However, the difference in xylem anatomy between treatments was not statistically significant, probably due to the high variability in the size of xylem vessels in individual plants. Larger xylem vessels would increase the water conduction capacity allowing for better development of the aerial portion of the plant. According to Poiseuille’s law, the water flow in a vascular conduit is related to its radius by a factor to the fourth power, meaning that a slight ...
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Citations
... However, incorporating a large quantity of clay-rich materials may negatively affect plant growth, as stated in this study, when the PS concentration exceeded 40% and mainly at 60%. Excess of clay fraction into the soil may cause several adverse effects when irrigated, such as waterlogging, which has led to roots asphyxiation and the reduction respiration activity of soil microorganisms (Gil et al., 2011). As reported in this study, smectite is the major fraction of PS clay minerals, which, due to its physical properties such as fine particle size, high surface area, and variable interlayer spacing, it could be the main responsible for clay effect on plant growth at 60% of PS (Dixon, 1991). ...
Phosphate sludge (PS) is an industrial by-product produced in huge quantities by the phosphate beneficiation plants in Morocco. In order to valorize this by-product, it was examined for its potential use as a soil fertilizer. The physicochemical properties, elemental and mineral content, morphological structure, and component stability of raw PS were investigated. In addition, pathogenicity, phytotoxicity, and the capacity of PS to promote plant growth in deficient sandy soil have been studied. The obtained results showed that PS was characterized by low values of moisture (2.10%), electrical conductivity (EC) (0.77 mS/cm), and organic matter (OM) (0.61%), with a slightly alkaline pH (8.20). Nevertheless, this material carried interesting content of fertilizing elements such as phosphorus (P2O5) of 20.01%, calcium (CaO) of 39.72%, and magnesium (MgO) of 2.33%. Thus, PS did not present any pathogenic or phytotoxic risk with a high increase in tomato plant growth than the control of only soil. In conclusion, the results of this study could provide the primary practical guidance for the PS application in deficient soils characterized by sandy texture.
... In the case of crop plants, oxygen-rich peroxides have been used, mainly as a seed treatment, to provide oxygen and to improve crop performance in wetland rice, and to improve germination of seeds [15]- [18]. In addition, use of hydrogen peroxide has been found to improve crop performance of avocado in poorly drained soils [19]. However, very little is known as to the relative effectiveness of these oxygen-rich compounds used in improving germination or plant performance under hypoxic conditions. ...
... Similar response was also observed with regard to various root growth characteristics. However, hydrogen peroxide has been traditionally used as a seed treatment to reduce the adverse effects of hypoxia in plants and in soil bioremediation [14] [15] [19]. Previous studies have shown that peroxide salts are more stable and may release oxygen more slowly than hydrogen peroxide [14] [28]. ...
Oxygen limiting conditions are a common occurrence in root zones of most crop plants and can adversely affect nearly all aspects of plant growth and development including its survival. The ob-jective of this study was to determine the effectiveness of a novel redox cycling agent, vitamin K 3 , and various peroxides including hydrogen peroxide, calcium peroxide and magnesium peroxide in alleviating the effects of hypoxia in bean seedlings grown in nutrient culture. All the anti-hypoxic agents including vitamin K 3 had a positive impact on the overall growth of bean seedlings under hypoxic conditions, but their responses were variable depending on the concentration. With re-gard to shoot growth, vitamin K 3 (5 μM) increased the leaf area significantly, by more than 58% over the hypoxic control plants and produced the highest stem fresh weight similar to calcium peroxide (20 μM) and magnesium peroxide (10 μM). In addition, the use of vitamin K 3 resulted in the highest accumulation of chlorophyll (chla + chlb) in the leaves, an increase of nearly two-fold over the hypoxic control plants. Furthermore under hypoxia, calcium peroxide (20 μM) and mag-nesium peroxide (10 μM) produced the highest leaf biomass (FW) followed by vitamin K 3 . Vitamin K 3 (1 μM) also favored root growth in bean seedlings under hypoxia; it produced the largest in-crease in root length and root biomass (DW) similar to calcium peroxide and magnesium peroxide. Based on the overall shoot and root growth response of bean seedlings to various anti-hypoxic substances under hypoxic conditions, calcium peroxide, magnesium peroxide and vitamin K 3 per-formed better than hydrogen peroxide. These findings show that vitamin K 3 and peroxide salts are * Corresponding author. C. B. Rajashekar et al. 3397 effective in alleviating hypoxic stress in bean seedlings and also, further highlight their potential for dealing with hypoxia in wide ranging situations.
