Understanding the impact that climatic factors have on cotton production may help physiologists to determine possible control mechanisms which influence the flowering of cotton plants. This study was conducted to investigate the nature of the effects of climatic factors prevailing prior and subsequent to either flowering or boll setting on flower and boll production and retention in Egyptian cotton Gossypium barbadense L. Two uniform field trials using the cotton cultivated variety Giza 75 were carried out at the Agricultural Research Center, Giza, Egypt. Randomly chosen plants were used to record daily numbers of flowers and bolls during the production stage (68 d in Season I and 62 d in Season II). The daily records of the climatic factors (air temperature, diurnal temperature range, evaporation, soil surface temperature, sunshine duration, and humidity) were recorded during the entire period of production and also for the 15 d periods before and after anthesis. The effects of climatic factors on flower and boll production were quantified in non-limiting management techniques. Relationships in the form of simple and multiple correlations were computed between climatic factors and flower and boll production and retention. The data indicated that evaporation, minimum humidity and sunshine duration were the most effective climatic factors during preceding and succeeding periods on boll production and retention. There was a negative correlation between flower and boll production and either evaporation or sunshine duration, while the same correlation with minimum humidity was positive. Thus, it appeared that low evaporation rate, reduced sunshine duration and high humidity would enhance flower and boll formation. Accordingly, the deleterious effects of climatic factors on cotton production could be minimized through applying appropriate production practices, which would control and adjust the impact of these factors and thus potentially lead to an important improvement in cotton yield in Egypt.KEY WORDS: Boll retention · Evaporation · Flower and boll production · Humidity · Sunshine duration · TemperatureResale or republication not permitted without written consent of the publisher

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Interval of days required for determining efficient relations between climatic factors and cotton flower and boll production. Can. J. Plant Sci. 82: 499-506. The cotton plant (Gossypium spp.) is sensitive to numerous environmental factors. This study was aimed at predicting effects of climatic factors grouped into convenient intervals (in days) on cotton flower and boll production compared with daily observations. Two uniformity field trials using the cotton (G. barbadense L.) cv. Giza 75 were conducted in 1992 and 1993 at the Agricultural Research Center, Giza, Egypt. Randomly chosen plants were used to record daily numbers of flowers and bolls during the reproductive stage (60 days). During this period, daily air temperature, temperature magnitude, evaporation, surface soil temperature, sunshine duration, humidity, and wind speed were recorded. Data, grouped into intervals of 2, 3, 4, 5, 6, and 10 d, were correlated with cotton production variables using regression analysis. Evaporation was found to be the most important climatic variable affecting flower and boll production, followed by humidity and sunshine duration. The least important variables were surface soil temperature at 0600 and minimum air temperature. The 5-d interval was found to provide the best correlation with yield parameters. Applying appropriate cultural practices that minimize the deleterious effects of evaporation and humidity could lead to an important improvement in cotton yield in Egypt.

In field trials at Giza in 1986-1987, cotton cv. Giza 75 was sown at 166,000, 222,000 and 333,000 plants/ha and given foliar applications of 0, 250, 500 and 750 ppm Cycocel {chlormequat) or Alar (daminozide}. As plant density increased, there was a decrease in cottonseed yield]ha, seed index, seed protein content, oil and protein yields/ha, oil refractive index, iodine value, unsaponifiable matter and unsaturated fatty acids {myristoleic, oleic and linoleic). In contrast, as plant density increased, there was an increase in oil acid value, saponification value and saturated fatty acids (caprylic, capric, lauric, tridecylic, myristic, palmitic and stearic). Application of Cycocel or Alar increased cottonseed yield/ha, seed index, seed protein content and oil and protein yield/ha, oil refractive index, iodine value, unsaponifiable matter and unsaturated fatty acids. However, there was a decrease in oil acid value and saponification value. There were no differences among application rates of either chemical on cottonseed yield/ha. The highest oil and protein yield/ha was observed with Cycocel applied at 750 ppm, followed by Aiar at 250 ppm. Applying Cycocel at 250 ppm gave the highest oil refractive index and unsaponifiable matter, and the lowest acid value. Application of Aiar at 250 ppm gave the highest oil iodine value and the lowest saponification value, and also at 250 or 500 ppm gave the highest oil unsaturated fatty acid composition. Interaction was positive between plant density, Cycocel and Aiar and affected cottonseed yield/ha. The 166,000 plants/ha and application of Cycocel at 750 and Aiar at 250 ppm are recommended for the improvement of cottonseed yield and quality.KEY WORDS: Cottonseed yield, growth retardants, oil fatty add composition, plant density, seed index, seed oil content, seed oil prope~ ties, seed protein content.