عنوان الرسالة/ معالجة أصول الحمضيات بالميلاتونين المعرضة للأجهاد الملحي وتأثيره في الصفات الفسلجية والكيموحيوية

Treatment of citrus rootstocks with melatonin exposed to salt stress and its effect on physiological and biochemical characteristics

Abstract:
The study was conducted in the plant canopy of the Department of Horticulture and Landscape at the College of Agriculture at Karbala University for the period from the beginning Until the middle of September2021, with three factors in order to know the effect of spraying with the growth regulator melatonin on the tolerance of some citrus rootstocks to salt stress. The first factor was the rootstocks (Swingle Citrumelo, Sour Orange and Volkamer lemon). As for the second factor, irrigation with three different salt concentrations (1.7, 4, and 8 d.s-1), and the third factor, spraying with the growth regulator melatonin with three concentrations (0, 50, and 100 mg.L-1), at a rate of 27 experimental units. The results were analyzed statistically using an analysis of variance table (A nova table) according to the Genstat (2010) program, and the Rates were compared using the least significant difference (L.S.D) under the probability level of 0.05.
The results can be summarized as follows:
The orange rootstock was significantly superior to the rest of the citrus rootstocks, and recorded the highest increase in the Rate plant height, which amounted to (85.960 cm), the diameter of the stem, which reached (8.214 mm), the number of leaves, which reached (77.09 leaf plant-1), and the leaf area, which amounted to (1692,000). cm2) As for the Volkamer lemon rootstock, it was significantly superior by registering the highest Rate dry weight in the vegetative shoots, which amounted to (29.380 gm), and the highest Rate in the dry root total, which amounted to (17.203 gm). The Rate content of leaves of chlorophyll, which reached (5.295 mg gm-1 fresh weight), the concentration of carbohydrates, which reached (18.635%), the concentration of nitrogen, which reached (1.518%), the concentration of potassium, which reached (1.425%), and the activity of the catalase enzyme, which reached (0.442). mg gm-1 fresh weight), and the activity of the peroxidase enzyme, which amounted to (90.413 IU gm fresh weight), and the content of ascorbic acid, which amounted to (96.287 mg in 100 gm-1 fresh weight). Proline, which reached (91.410 mg gm-1), the sodium concentration, which reached (0.216%), and the concentration of Chloride, which amounted to (1.005%), while the rootstock Swingle Citrumelo recorded a significant superiority by registering the highest Rate in the content of phosphorous in the leaves, which amounted to (0.301%).
Irrigation with electroconducting water (1.7 d.s-1) resulted in a significant increase in the Rate vegetative and root characteristics of the plant height, which reached (82.740 cm), the diameter of the stem, which reached (7.638 mm), and the number of leaves, which reached (88,630 leaf plant-1). The leaf area amounted to (2114 cm2), the Rate dry weight of the vegetative Shoots amounted to (034.72 gm), the Rate dry weight of the root system reached (19.827 gm), and the Rate root length reached (39.740 cm). Obtaining the highest values in the Rate of the biochemical growth characteristics in the leaves, which are the chlorophyll content, which amounted to (6.354 mg per 100 gm-1 fresh weight), the carbohydrate concentration, which reached (19.567%), the nitrogen concentration, which reached (1.734%), and the phosphorus concentration, which reached (1.734%). (0.397%), and the concentration of potassium, which amounted to (1.380%), while irrigation with electrolyte water (8 d.s-1) resulted in obtaining the highest values in the Rate biochemical characteristics, which is the activity of the catalase enzyme, which amounted to (0.475 mg g-1 fresh weight). And the activity of the peroxidase enzyme, which reached (101.340 IU gm fresh weight) and the content of ascorbic acid, which reached (95.113 mg). m 100 gm-1 fresh weight), the proline content amounted to (115.177 mg gm-1), the sodium concentration reached (0.248%), and the chloride concentration reached (1.332%).
The treatment of foliar spraying with the growth regulator melatonin at a concentration of (100 mg L-1) showed the highest Rate in the characteristic of plant height, which reached (382.83 cm), stem diameter, which reached (8.127 mm), and number of leaves, which reached (76,410 leaves plant-1), and The leafy area amounted to (1603.333 cm 2), the dry weight of the vegetative Shoots amounted to (28.180 gm), the dry weight of the root system reached (16.077 gm), and the root length reached (36.407 cm). mg L-1) the highest Rate in the biochemical characteristics, which is chlorophyll, giving the highest Rate (4.672 mg gm-1 fresh weight), carbohydrates (17.162%), nitrogen (1.507%), phosphorus (0.290%), potassium (1.359%), catalase reached (0.405 mg gm-1 fresh weight), and ascorbic acid reached (90.127 mg 100 gm-1 fresh weight).
The binary and triple interactions between the study factors led to a clear significant superiority in the studied traits compared to the comparison treatment. Plant height, stem diameter, leaf area, leaf chlorophyll content, carbohydrate concentration, nitrogen, potassium, peroxidase activity, catalase, ascorbic acid content amounted to (111.880 cm), (9.477 mm), (2848 cm2), and (7.819 mg gm-1). fresh weight),(24.733%), (2.097%), (1.549%), (63.230 IU gm-1 fresh weight), (0.286 mg gm-1 fresh weight) and (91.370 mg gm-1 fresh weight), respectively, while the triple overlap treatment (Swingle Citrumelo rootstock + Melatonin at a concentration of 100 mg L-1 + Irrigation water salinity at a concentration of 1.7 d.s-1) recorded the highest Rate leaf concentration of phosphorus, which amounted to (0.439%). 1 + Irrigation water salinity with a concentration of 1.7 d.s-1), the highest mean in the number of leaves, which reached (95,170 leaf plant-1). The Rate root length reached (42.670 cm), the Rate dry weight of the shoot reached (38.960 gm), and the Rate dry weight of the root total reached (72.290 gm). While the treatment of triple interaction (Volkamer lemon rootstock + melatonin at a concentration of 0 mg L-1 + irrigation water salinity at a concentration of 8 ds-1) recorded the highest Rate in the leaf content of proline, which reached (180.330 mg gm-1).