الفهرس 
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Abstract
SUMMARY
The field experiments were conducted at Nubaria Agricultural Research Station, Agricultural Research Center (ARC), El-Behira Governorate, Egypt (30°55′27.6′′N, 29°56′57.8′′E). during two successive summer seasons 2019 and 2020. To study the effect of three drought tolerance inducers with two concentrations (glycine betaine (GB) 400 and 200 mg l-1, proline 100 and 50 mg l-1and chitosan 300 and 100 mg l-1) were used compared with control (untreated plants) under water stress, through prolonging the irrigation interval (every 10, 15 and 20 days starting after the first irrigation throughout the growing season) on growth, productivity and some chemical properties of Giza 94 cotton cultivar.
Characters under study:
I– Vegetative growth characters: - (70, 90, 110 days from sowing).
1. Plant height(cm).
2. Total dry weight per plant (g).
3. Dry weight of bolls per plant (g).
4. Leaf area/plant (dcm2).
II- Growth characters and earliness traits at harvest
1. Plant height(cm).
2. Number of fruiting branches per plant.
3. Position of first fruiting node.
4. Number of days to first flower.
5. Number of days to first open boll.
III - Yield and yield component
1. Number of open bolls per plant.
2. Boll weight (g).
3. Seed index (g).
4. Lint % .
5. Seed cotton yield (ken. /fed.).
IV- Fiber quality
1. Fiber length (mm).
2. Uniformity index.
3. Fiber strength (g/tex).
4. Micronaire reading.
IIV- Chemical Properties
1. Proline.
2. chlorophyll A, B and total chlorophyll.
3. Total soluble sugars(in leaves).
The obtained results can be summarized as follows:
I– Vegetative growth characters
1- Data obtained that all studied growth characters (plant height, total dry weight per plant, bolls dry weight\ plant, leaf area\plant) in the three sampling 70, 90, 110 days after sowing (DAS) decreased significantly with prolonging irrigation intervals to 15 and 20 days compared with irrigation every 10 days in both seasons 2019 & 2020
2- Data also revealed that all drought tolerance stimulation (i.e. Glycine betaine, Proline and Chitosan) gave positive enhancement on all studied growth characters in the three sampling 70, 90, 110 days after sowing (DAS) compared with untreated ones, where it was found superiority in favor of glycine betaine (400 mg l-1) compared to other drought tolerance inducers.
3- The effect of drought tolerance stimulus and irrigation periods on studied growth characters at 70, 90 and 110 DAS in both seasons was significantly except plant height after 70 and 110 DAS, total dry weight per plant after 70 DAS, bolls dry weight\ plant after 90 DAS in the first season (2019) were un-significant. In addition all drought tolerance stimuli were improved growth of cotton plant under different irrigation periods.
II- Growth characters and earliness traits at harvest
1. Growth traits (i.e., plant height and fruiting branches No plant-1) were significantly affected by irrigation intervals and drought tolerance inducers. Plant height and fruiting branches No plant-1 were decreased with prolonging irrigation intervals from 10 to 20 days
2. Data cleared that earliness indicators (i.e. days No. to first flower and days No. to first open boll) were significantly affected by irrigation intervals and drought tolerance inducers. Whereas, prolonging irrigation intervals from 10 to 20 days led to an earlier of No. of day to first flower and open boll in both 2019 and 2020 seasons. while, position of first node was insignificantly affected by irrigation intervals. On the other hand, foliar application with drought tolerance inducers delayed day No. to first flower, day No. to first open boll compared to the control in 2019 season. Whereas, foliar application with Glycine betaine 400 mg was the most delaying day No. to first flower. first open boll compared to untreated (control) in 2019 season. While, foliar application with chitosan 100 mg l-1 achieved earliest day No. to first flower and No. of day to first open boll in 2020 season.
3. Interaction between irrigation intervals and drought tolerance inducers was significantly effect on plant height, fruiting branches No. plant-1 and position of first node in 2019 and 2020 seasons. Foliar application with glycine betaine 400 mg l-1 under irrigation interval recorded the highest values in the previous traits. On the other hand untreated (control) combination with irrigations interval 20 days was the superior interaction treatment that achieved the earliest day No. to first flower and proline 100 mg l-1 combination with irrigations interval 20 days was the higher interaction treatment that showed the earliest day No. to first open boll in 2020 season while, were insignificantly effected in 2019 season.
III- yield and yield components:
1-Irrigation intervals significantly effect on open bolls No. plant-1, weight of bolls, weight of 100 seed, lint percentage and cotton yield fed-1 in 2019 and 2020 seasons. Prolonging irrigation intervals to 15 and 20 days significantly reduced open bolls No. plant-1, boll weight, seed index and seed cotton yield/fed., while lint % was significantly increased compared with irrigation interval 10 days in, respectively.
2-Data also showed that drought tolerance inducers significantly effect on open bolls No. plant-1, weight of boll, weight of 100 seed, lint percentage and cotton yield fed-1 in 2019 and 2020 seasons. Additionally application with glycine betaine 400 mg l-1 was enhancement all pervious studied traits compared with untreated (control).
3-Interaction between drought tolerance inducers and irrigation intervals it was significant on yield and yield attributes. As indicated in application of drought tolerance inducers mitigate the effect of prolong irrigation intervals on cotton plant. Foliar application with all drought tolerant inducers were achieved a higher values with irrigation interval 15 days compared with untreated (control) under irrigation interval 10 days with open bolls No. plant-1, weight of boll, weight of 100 seed and cotton yield fed-1 in 2019 and 2020 seasons.
IV- Fiber properties
Fiber length, uniformity index, fiber strength and micronare value decreased significantly gradually, with Prolonging irrigation intervals from 10 to 20 days. Regarding the effect of drought tolerance inducers on fiber properties data showed that glycine betaine 400 mg l-1 improvement fiber length in 2019 season by 2.8% and by 4.1% with glycine betaine 200 mg l-1 in 2020 season outperformed untreated (control). On the other hand glycine betaine 200 mg l-1 gave the highest significantly value of micronare in 2019 season, while the drought tolerance inducers were insignificant effect of uniformity index and fiber strength in 2019 and 2020 seasons and micronare in 2020 season. For the interactions between irrigation intervals and drought tolerance inducers, there were non-significant effect on all fiber properties exception micronare was recorded the highest value when cotton plant treated with glycine betaine 200 mg l-1 under irrigation interval 10 days in 2019 season.
IIV- Chemical Properties
Irrigation intervals effect on Physio-chemical traits significantly and chlorophyll a, b and total chls decreased gradually significantly, while Proline and total soluble sugars showed a significant progressive increase, with prolonging irrigation intervals from 10, 15 to 20 days in 2020 season. Drought tolerance inducers, caused significant increases for all studied Physio-chemical traits i.e. the chlorophyll a, b, total chls, Proline and total soluble sugars. Interaction between drought tolerance inducers and irrigation intervals it was significant. Data also showed that foliar application with glycine betaine 400 mg l-1 X irrigations interval 10 days was the best combined treatment that recorded the highest values for chlorophyll a and total chls. While, the highest value of chlorophyll b was recorded with glycine betaine 200 mg l-1 X irrigations interval 10 days. In general, the use of glycine betaine 200 & 400 mg l-1 and proline 50 & 100 mg l-1 made the plants more tolerant of prolong irrigation intervals, as higher values were recorded with irrigation interval 15 days compared with control under irrigation interval 10 days in chlorophyll measurements.