Date of Award

5-2002

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Science

First Advisor

Dr. Karim Mohamed Farag

Second Advisor

Dr. Ail A. M. El-Keblawy

Third Advisor

Dr. Hameed Jasim Al Jubure

Abstract

This research was conducted during the period of 2001/2002 to determine the thermotolerance of date palm leaflets reproduced by tissue culture and compared that with the tolerance of offshoot for the same cultivar Rzaiz. Heat tolerance of these leaflets in the presence of high salt concentration was also determined. Tissue culture plantlets used in this investigation were at two stages of acclimatization, namely VP2 and VP3 (vitro plants under acclimation program for about 4 to 6 months and 10 months, respectively). Rzaiz offshoots attached to the mother plants were about 4 years old. The electrolyte leakage procedure was used to generate sigmodial curves, and from each curve the thermotolerance was determined at 50 % electrolyte leakage. Leaflets of the three stages of growth and development (VP2, VP3 and offshoot) were treated in the laboratory with each of heat, heat plus NaCI, heat plus KCI, Heat plus CaCI2, heat plus oleic acid, heat plus salt and oleic acid, heat plus salt and KCI and heat plus salt and CaCI2. Concentrations were: NaCI at 1 % w/v (mentioned as salt), KCl or CaCl2 (0.2 M) or oleic acid at 100 ppm. Treatments by various chemicals was done by dipping leaflet segments for 1 hr before going through the heat regime (series of temperatures ranged between 30 to 75 °C with 5 °C incrementes).

A completely randomized design was used with three replications. Thermotolerance values were 53°C, 53.5 °C, and 58.5 °C for VP2, VP3, and offshoot leaflets, respectively.

Pretreatment with potassium chloride, calcium chloride, or oleic acid markedly increased the thermotolrerance of leaflets. The used NaCI concentration was not effective 10 lowering the leaflet thermotolerance. However, heat plus salt treatment resulted in significantly higher electrolyte leakage than heat plus salt in the presence of oleic acid, KCI, or CaCl2 at sub lethal temperatures. Moreover, VP2 leaflets had higher electrolytes leakage than VP3 leaflets at sub lethal temperatures, even though their lethal temperature did not greatly vary.

Investigations in this thesis provided for the first time an accurate determination for heat tolerance of the two acclimatization stages that are distributed to date palm growers. Results also revealed that there is a potential to increase the thermotolearance of VP2, VP3, or offshoots that could increase their survival under field conditions.

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