الفهرس | Only 14 pages are availabe for public view |
Abstract SUMMARY Two field experiments were carried out during 2012 and 2013 seasons at Agricultural Experimental Station in Ras Sudr Research Station, Desert Research Center, at South Sinai Governorate, Egypt, to study the effect of interaction between three periods of irrigation (4 day - 8 day – 12 day ) and four soil additives ( Potassium humate, silicon, mixture of both and control tap water) on the growth, yield and chemical composition of two pearl millet cultivars (Shandawyl 1 and Sudan pop I) under saline condition. The main results could be summarized as follows: 1. Growth Traits Irrigation intervals had significant effect on growth parameters (plant height, number of tillers/ plant, fresh weights, dry weights and leaf area) of pearl millet cultivars. The increase in growth was achieved with irrigation every 4 day treatment as compared with the other two irrigation treatments (8 day and 12 day) during 1st cut and 2nd cut in both growing seasons. All growth traits significantly increased with all soil additives as compared with the control during both seasons. However, silicon treatment recorded the higher mean values for plant height, number of tillers/m2, fresh and dry weights as well as leaf area during 1st cut and 2nd cut in both growing seasons. Meanwhile, potassium humate and the mixture (silicon + Potassium humate) recorded the 2nd and 3rd order, respectively. Generally, significant response was shown in all growth characters of the two pearl millet cultivars. However, Sudan pop I Summary 203 cultivar exhibited the highest mean values for all growth traits during 1st cut and 2nd cut in both growing seasons. Concerning the effect of interaction between irrigation intervals X soil additives X pearl millet cultivars on growth traits under Ras Sudr conditions, the interaction between 4 day irrigation interval with silicon as a soil additive for Sudan pop I cultivar gave the highest mean values of plant height, number of tillers/m2, fresh and dry weights as well as leaf area during 1st cut and 2nd cut in both growing seasons. Also, application of potassium humate as a soil additive with 4 day irrigation interval for Sudan pop I cultivar recorded the 2nd order during 1st cut and 2nd cut in both growing seasons. Generally, plant height, number of tillers/m2, fresh and dry weights of pearl millet plant recorded the highest mean values during the 1st cut in 1st season while leaf area recorded the highest mean values during the 1st cut in 2nd season. 2. Chemical composition Plant hormones: Concerning endogenous phytohormones, the interaction between 4 day irrigation intervals with silicon as a soil additive for Sudan pop I cultivar gave the highest mean values of IAA and GA3 followed by The interaction between 4 day irrigation interval with silicon as a soil additives for Shandawyl 1 cultivar. Also, application of tap water as a soil additive with 12 day irrigation interval for Shandawyl 1 cultivar recorded the lowest mean values of IAA and GA3. Concerning ABA level, the highest mean value for ABA was produced from the interaction between tap water as a soil additive with 12 day irrigation interval for Shandawyl 1 cultivar followed by the interaction between 12 day irrigation interval with tap water as a soil additive for Sudan pop I Summary 204 cultivar. However, the lowest mean value for ABA was produced from the interaction between 4 day irrigation interval with silicon as a soil additive treatment for Sudan pop I cultivar. Photosynthetic pigments: Irrigation interval treatments increased significantly pigment contents as compared with the control. Chlorophyll (a), chlorophyll (b), carotenoids, chlorophyll (a+b) and total pigments recorded the highest mean value due to 4 day irrigation interval, whereas the lowest value of these parameters were recorded due to irrigation interval every 12 day. All soil additives increased significantly pigment contents as compared with the control. Silicon treatment recorded the highest mean values for chlorophyll (b) contents compared with other treatments. However, Potassium humate produced the highest mean values for chlorophyll (a), chlorophyll (a+b), carotenoids and total pigments. Sudan pop I cultivar significantly exceeded Shandawyl 1 cultivar in chlorophyll (a), chlorophyll (b), chlorophyll (a+b), carotenoids and total pigments. The interaction between 8 day irrigation interval with potassium humate as a soil additive for Sudan pop I cultivar gave the highest mean values of chlorophyll a, chlorophyll a+b and total pigments. Also, application of potassium humate as a soil additive with 4 day irrigation interval for Sudan pop I cultivar recorded the highest mean values of chlorophyll b. However, the interaction between 4 day irrigation interval with control as a soil additive for Sudan pop I cultivar gave the highest mean values of carotenoids. Summary 205 Carbohydrate contents: Irrigation interval treatments had significant effect on carbohydrate contents. It is clearly shown that 4 day irrigation interval produced the highest mean values for total carbohydrate and nonsoluble carbohydrate contents. While, 12 day irrigation interval treatment marked the highest mean values for soluble sugars. All soil additives had significant effect on carbohydrate contents as compared with the control (tap water). It is clearly shown that silicon produced the highest mean values for carbohydrate contents (total carbohydrate, soluble sugars and non-soluble carbohydrate contents) followed by soil additive with potassium humate. Sudan pop I cultivar produced the maximum value of total carbohydrate and non-soluble carbohydrate contents. While, Shandawyl 1 cultivars marked the highest mean values for soluble sugars. It is evident from these results that the interaction between 4 day irrigation interval with silicon as a soil additive for Sudan pop I cultivar recorded the highest mean values of total carbohydrate and non-soluble carbohydrate contents followed by the interaction between 4 day irrigation interval with silicon as a soil additive treatment for Shandawyl 1 cultivar. Meanwhile, the interaction between 12 day irrigation interval treatment with silicon as soil additives treatment for Shandawyl 1 cultivar recorded the highest mean value for total soluble sugars contents followed by the interaction between 12 day irrigation interval with silicon as a soil additive for Sudan pop I cultivar. Summary 206 Protein and proline contents: Irrigation interval treatments had significant effect on total protein, soluble and non-soluble protein and proline contents. Irrigation every 12 day marked the highest mean values for proline content and irrigation every 4 day recorded the highest mean values for total protein, soluble and non-soluble protein in pearl millet plants. All soil additives had significant effect on proline and Proteins (total, soluble, non-soluble) contents as compared with the control (nontreated). It is clearly shown that silicon produced the highest mean values for proteins (total, soluble, non-soluble) contents as compared with the other treatments. Generally, significant response was found in proline and proteins contents of the two pearl millet cultivars. However, pearl millet Sudan pop I cultivar exhibited the highest mean values of proline and proteins (total, soluble, non-soluble) contents. The highest values of total protein, soluble and non-soluble protein contents were recorded by the interaction between 4 day irrigation intervals with silicon as soil additive for Sudan pop I pearl millet cultivars as compared with the other treatments. While, the interaction between 12 day irrigation interval with silicon as a soil additive for Shandawyl 1 cultivar recorded the highest mean value of proline content. Summary 207 Amino acids content: Seventeen amino acids were detected in shoots of pearl millet plant. They are aspartic acid, glutamic acid, arginine, alanine, proline, leucine and valine appeared in higher amounts in the shoots of pearl millet plant. Water stress induced a massive increase in total amino acids detected in the shoot of two pearl millet cultivars. Soil additives with potassium humate, silicon and mixture of potassium humate and silicon and their interaction induced additional increases in the detected amino acids content when compared with control (tap water) in shoots of two pearl millet cultivars. The interaction between silicon as soil additive with 12 day irrigation interval treatment for Sudan pop I cultivar recorded the highest value of total amino acids content followed by the interaction between potassium humate as soil additive with 12 day irrigation interval treatment for Sudan pop I cultivar. Whears, the interaction between tap water as soil additive with 4 day irrigation interval treatment for Shandwyl 1 cultivar recorded the lowest value of total amino acids content. Minerals composition: Irrigation interval treatments had significant effect on minerals composition. It is clearly shown that 4 day irrigation interval produced the highest mean values for Mg, Ca, P and and K contents. While, 12 day irrigation intervals treatment marked the highest mean value for Na contents. Mg, K, Ca and P contents were significantly increased with all soil additive treatments as compared with the control . On the contrary, Na content was decreased with all soil additive treatments. Soil additives Summary 208 with silicon produced the maximum value of Mg, K, Ca and P contents as compared with the other treatments. On the other hand, control marked the highest mean value for Na content. Sudan pop 1 cultivar produced the maximum value of Mg, Ca, K and P contents. A reverse effect was observed for Na content. It is evident from present results that 12 day irrigation interval with control as a soil additives treatment for Shandawyl 1 cultivar recorded the highest mean value of Na content. Meanwhile, 4 day irrigation interval treatment with silicon as soil additives treatment for Sudan pop I cultivar recorded the highest mean value for P, Ca and Mg contents. Also, 4 day irrigation interval treatment with potassium humate as soil additive treatment for Sudan pop I cultivar recorded the highest mean value for K contents. The above results revealed that soil additives with potassium humate, silicon and mixture of potassium humate + silicon and their interaction with irrigation interval treatments increased Mg, K, Ca, and P contents, while, decreased Na level when compared with control . This response is much more pronounced in Sudan pop I cultivar indicating that Sudan pop I cultivar is more tolerant than Shandawyl 1 cultivar. Antioxidant enzymes: The activities of catalase (CAT), ascorbate peroxidase (APX) and peroxidase (POX) were increased in response to drought stress. Irrigation at 12 day interval treatment recorded the highest main value of these enzymes as compared to 8 and 4 day irrigation interval treatments. In general, all soil additives increased the activities of catalase (CAT), Summary 209 ascorbate peroxidase (APX) and peroxidase (POX) as compared to the control. SOD patterns revealed the presence of three bands for the two pearl millet cultivars. The more intensive band is presented at band number 2 followed by band number 1 in two pearl millet cultivars with all treatments under drought stress. Concerning band intensity, data showed that irrigation intervals had a positive effect on band intensity under salinity stress. Band intensity increased in all samples under 12 day irrigation interval compared with the 8 day and 4 day irrigation intervals treatments. Also, all soil additives by potassium humate, silicon and the mixture between both increase band intensity as compared with the control. Lipid peroxidation (Malondialdehyde), Ascorbic acid, total phenols and total flavonoids: Irrigation at 12 day interval produced the highest mean values for Malondialdehyde, ascorbic acid, total phenols and flavonoids followed by 8 day irrigation interval treatment as compared with 4 day irrigation interval treatment. Ascorbic acid, total phenols and total flavonoid conents were significantly increased with all soil additives as compared with the control (tap water). While, malondialdehyde significantly decreased with all soil additives as compared with the control (tap water). Soil additives with silicon produced the maximum value of ascorbic acid, phenols and flavonoid conents as compared with the other treatments. Summary 210 Generally, significant response was found in malondialdehyde, ascorbic acid, total phenol and total flavonoid contents of the two pearl millet cultivars. However, pearl millet Sudan pop I cultivar exhibited the highest mean values of ascorbic acid, total phenols and total flavonoid contents. Whereas, pearl millet Shandawy l cultivar exhibited the highest mean values of malondialdehyde. |