الفهرس 
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Abstract
This work was carried out to study the effect of pre-sowing irradiation and Zn treatments on germination, growth and nutritional status of Cleopatra mandarin and Sour orange.
In this respect, two series of experiments were conducted during the period from April, 2001 till Dec., 2003 as follows:
First Series:
These experiments were designed to study the effect of pre-sowing gamma irradiation with low doses on seed germination, growth and nutritional status of two citrus rootstocks. Seeds of Cleopatra mandarin and Sour orange were irradiated before sowing with gamma rays at 0.0, 10, 20, 40 and 80 Gray (Gy). Germination process was conducted in the nursery. After 6 months, seedlings were transplanted in polyethylene bags and recieved the normal agricultural practices till the end of experiment.
The required parameters and samples were taken and the proper analysis was done:
Second Series:
These experiments were also designed to study the effect of pre-sowing seeds soaking with ZnSO4 on seed germination, growth and nutritional status of both rootstocks plants. Seeds of both were soaked before sowing in ZnSO4 solutions to give 0.0, 0,05, 0.10, 0.20 and 0.40 % Zn for 12 hrs. There after, the same procedures of the first part, previously mentioned, were applied to achieve these experiments.
In this regard, effect of pre-sowing irradiation and seeds soaking with ZnSO4 on germination, growth, leaf pigments content
nutritional status of Cleopatra mandarin and sour orange was studied.
The important results could be summarized as follows: First part:
1.Irradiating Cleopatra mandarin and Sour orange seeds before sowing with low gamma doses ”20 and 40 Gy ” considerably and significantly promoted and accelerated germination process • of both rootstocks, which increased germination percentage, germination rate and shortened the required period for 50% germination.
2.Low gamma doses, in particular at 20 Gy, considerably and significantly stimulated plant growth of Cleopatra mandarin
. and Sour orange which in turn greatly increased plaid height, stem diameter, leaves number and total leaf area per plant, fresh and dry weight of plant parts as well as the whole plant.
3.Response of Sour orange to gamma irradiation was more pronounced than Cleopatra mandarin as far as seed germination process and plant growth were concerned.
4.Leaf pigments content, namely, chlorophyll (a), chlorophyll (b) and carotenoids of both rootstocks were highly and significantly increased as a result of low gamma doses with maximum increase at 40 Gy. However, increasing rate of the two components of chlorophyll due to gamma doses was higher in Sour orange than in Cleopatra mandarin,
5.Levels of the estimated nutrient elements in different plant parts of Cleopatra mandarin and Sour orange, i.e. N, P, K, Fe and Zn, were not significantly affected by the tested range of gamma doses. Whereas, Mn level in leaves and stems of both plants was
significantly increased by doses at 20 or 40 Gy. Moreover, there was no significant difference between the two rootstocks in this concern.
6.Using low gamma doses, particularly at 20 Gy, markedly and significantly increased total content of N, P, K, Fe, Mn and Zn in different plant parts, i.e. leaves, stems and roots of Cleopatra mandarin and Sour orange.
7.Total uptake of these nutrients by both plants was considerably and significantly encouraged by gamma doses ranged from 10 to 40 Gy with maximum increase at 20 Gy. But increasing rate of total uptake of all studied nutrients due to 20 Gy was more pronounced with Sour orange than with Cleopatra mandarin. However, means of total uptake of these nutrients by Cleopatra mandarin exhibited significant increase comparing to those of sour orange.
8.Response of total uptake of different nutrients by both plants to the tested range of gamma doses, especially at 20 Gy, varied where Mn exhibited highest response followed by both Zn and Fe, P, and by N and K.
Second part:
9.he-sowing seed soaking in ZnSO4 solutions, in particular at 0.2 % Zn, markedly promoted and accelerated germination process of Cleopatra mandarin and Sour orange seeds. In this regard, germination percentage and germination rate were significantly increased by Zn treatments, while the required period for 50 % germination was reduced. Moreover, germination parameters of Sour orange were better than those of Cleopatra mandarin.
10.Zinc sulfate application, in particular at 0.2 % Zn, highly stimulated plant growth of both rootstocks and consequently
caused significant increase in plant height, stem diameter, total leaf area, fresh and dry weight of plant parts as well as total accumulation of dry matter yield of the whole plant. Moreeover, Sour orange seedlings were characterized with highest accumulation of dry matter in their leaves, stems, roots and whole plant comparing to Cleopatra mandarin seedlings.
11 Leaf contents of chlorophyll (a), (b) and carotenoids were
greatly and significantly increased by ZnSO4 application, particularly at 0.2 %. Moreover, leaf content of both components of chlorophyll ” a & b ” was significantly more with Sour orange than with Cleopatra mandarin.
12.Levels of N, P, K and Zn in different plant parts were not significantly affected either by ZnSO4 treatments, or by rootstocks. Whereas, Fe level was higher in Sour orange parts than in Cleopatra mandarin. Moreover, Mn level in leaves was increased by Zn at 0.05 % and that in stems and roots was increased by 0.1 or 0.2 % Zn.
13.Total content of N, P, K, Fe, Mn and Zn in different parts of both plants was significantly increased by ZnSO4 application in particular at 0.2 % Zn, which in turn greatly increased total uptake of these nutrients by two rootstocks plants.
14.Maximum uptake of the studied nutrients by plants as affected by Zn treatments seemed to be dependent on rootstock and a nutrient, where maximum response of Sour orange plants was more pronounced than that of Cleopatra mandarin. In addition, highest response of total uptake due to Zn treatments was • obtained by Mn (58- 64 % inc ease) followed by Zn and Fe ( 58 % increase); P (55- 58% increase); K (54 -56 % increase) and by N (49- 54% increase ).