The results obtained can be summarized as follows:
1. Drought stress
a. Drought stress on cotton plants led to decreased pigments (Chl a, b, total Chl. and caroteinoids contents) in Giza 90 and Giza 92 cultivars by (27.58%, 18.83%, 23.73% and 24.05%) and (28.98%, 29.17%, 29.07% and 37.72%) respectively.
b. Drought conditions tended to decrease reducing (55.26% and 62.18%), non reducing (16.23% and 39.93%) and total soluble sugars (45% and 54.88%) in Giza 90 and Giza 92 cultivars respectively.
c. Water stress reduced total phenols content in Giza 90 and Giza 92 cultivars (13.67% and 24.34%), total free amino acids (30.96% and 40.06%), total soluble protein contents (54.54% and 62.46%) and catalase activity (66.45% and 20.26%) respectively.
d. Drought stress on cotton plants led to increased proline (311.83% and 630%), total antioxidant capacity (87.78% and 65.57%) and peroxidase activity (207.15% and 204.85%) in Giza 90 and Giza 92 cultivars respectively, while seed contents (oil, protein and nitrogen) were decreased as compared with control plants (turgid) by (20.56%, 29.52% and 47.12%) in Giza 90 cultivar and Giza 92 cultivar (20.14%, 21.01% and 37.39%) respectively.
e. Drought due to decrease growth characters as compared with control plants (turgid) in the two cultivars (Giza 90 and Giza 92) in the two seasons.
f. Seed cotton yield were decreased as a result to drought conditions in season 2010 (8.04% and 31.4%) and season 2011 (7.06% and 30.71%) Giza 90 and Giza 92 cultivars respectively.
2. Effect of sodium nitroprusside, putrescine and glycine betaine
a. Exogenous application of SNP, Put and GB with different concentrations on cotton plant under drought stress led to improve physiological, morphological and chemical constitution of cotton. So it can use them for cotton plant tolerance of drought stress. The best treatment was spraying cotton plants with GB (800 ppm) then Put (600 ppm) and SNP (0.05 mM) in the two cotton cultivars.
b. The most effective treatment was spraying Giza 90 and Giza 92 cultivars with GB (800 ppm) which increased pigments (chl. a, b, total chl. and caroteinoids) by (29.59%, 28.51%, 29.09% and 26.36%) and (14.25%, 23.15%, 18.64% and 30.43%) respectively, carbohydrates (reducing, non-reducing and total soluble sugars) by (66% 45.33% and 59.93%) and ( 63.57%, 41.39% 56.11%) respectively, total phenols (35.66% and 34.58%), proline (52.82% and 54.05%), total amino acids (29.46% and 38.33%), total soluble protein (15.2% and 28.72%), increasing activity of catalase (73.31% and 31.6%) and peroxidase (36.33% and 17.74%) and increase total antioxidant capacity (7.61% and 29.63%) in cotton leaves. Also, increased oil, protein and nitrogen contents by (14.37%, 18.94% and 20.36%) and (17.48%, 18.63% and 31.85%) in seeds of Giza 90 and Giza 92 cultivars respectively as compared with drought stress plants.
c. Exogenous application of GB on cotton plant improved growth characters in the two cotton cultivars in two experimental seasons as compared with drought stress plants.
d. Exogenous application of GB (800 ppm) increased seed cotton yield in the Giza 90 and Giza 92 cultivars in season 2010 (43.1% and 19.52%) and season 2011 (40.39% and 34.6%) respectively as compared with drought stress plants.

The present work was designed to study the relations between some factors affecting boll opening and cotton yield and quality of Egyptian cotton. Eight Egyptian cotton cultivars were chosen representing the two categories of Egyptian cotton (1- Extra long staple cultivars i.e. Giza- 45, Giza- 70 and Giza- 88, and 2- long staple cultivars i.e. Giza- 85, Giza- 86, Giza- 89, Giza- 80 and Giza- 83). These cultivars were planted in two seasons 2001 and 2002 at different five locations i.e. Kafr El- Sheikh, El – Beheira, Giza, El- Faiyum and El –Minia. Yield and yield components as well as fiber quality and some of earliness traits were investigated. Phenotypic and genotypic correlation coefficients were computed for these traits. Stepwise analysis was done to identify the contribution of some affecting factors on boll opening and cotton yield and quality traits.
Significant differences were found between the studied varieties in the studied traits. Seasons of growing significant affected for all traits except fiber fineness and strength, while locations and locations x seasons interaction showed significant effects on all traits. Genotypes x Seasons interaction affected significant on all traits except boll weight and fiber strength. The cultivars x seasons x locations interactions affected significant on all traits except boll weight.
High values of the heritability were obtained more than 50% except for seed cotton yield and No. of bolls/plant which were 45.3% and 49.1%, respectively. Consequently, the values of the expected gain from selection were very high and more than 30% except for days to first flower and days to first boll opening which gave 21.1% and 13% respectively.
Positive and significant phenotypic correlation were obtained between boll age and each of uniformity ratio, seed index, 50% span length, days to first flower and days to first boll opening for most cotton varieties under study. Also, the correlation between days to first flower and each of boll weight and days to first boll opening was positive and significant for most cotton varieties, while it was negative and significant for lint percentage for Giza 89 and Giza 83 cultivars, respectively. The correlation between days to first boll opening and each of boll weight uniformity ratio, days to first flower and boll age were positive and significant, while it was negative and significant with lint percentage for Giza 83 and Giza 89 cultivars. Genotypic correlation between days to first flower and both No. of bolls /plant and seed index was negative. Moreover, days to first boll opening was negatively correlated with No. of bolls /plant and seed index.
The results of stepwise analysis of the factors affecting on boll opening, yield and quality of cotton showed that the boll characteristics i.e. boll diameter, bract area and bract width had a direct effect on boll age, days to first boll opening and uniformity ratio, respectively, while valve base width, bract length and flower neck length had inverse effect on boll weight, boll age and lint percentage, respectively.
The environmental factors were studied; total bright sunshine hours in the seventh week after flowering, mean of maximum temperature in the fifth week after flowering and mean of minimum relative humidity in the sixth week after flowering had inverse effect on boll weight, boll age and days to first boll opening, respectively, while mean of minimum temperature, total bright sunshine hours and mean of maximum temperature in the third week after flowering had a direct effect on 50% span length, boll weight and lint percentage.