Effect of X-irradiation on Proline Accumulation, Growth and Water Content of Date Palm (Phoenix dactylifera L.) Seedlings

Ionizing radiation induces physiological changes which activate stress-reaction mechanisms inciting proline accumulation in plants. The effects of radiation differ according to plant and dose parameters. The present study was conducted to determine the effects of different doses of X-rays on seedlings of date palm (Phoenix dactylifera L.). Seedlings collected from cv. Khalas were exposed to 0-1500 rad using a medical X-rays device. After exposure, the seedlings were grown in soil and growth was measured in terms of fresh and dry weight of roots and leaves. Accordingly, water content of root and leaf tissues was calculated. Proline content of leaf tissue was spectrophotometrically determined. The results showed that the X-rays dose affected proline accumulation and growth parameters of date palm seedlings. A direct relationship between the radiation dose and proline content was observed. Based on measurements of proline content, the minimum dose of X-rays that causes a significant stress reaction in date palm seedling is 100 rad. Exposure to X-rays caused noticeable increases in fresh and weight as well as water content of both leaf and root tissues. Significant changes in fresh and dry weights as well as water content of root and leaf tissues were observed with low doses ranging from 5 to 10 rad. Higher doses caused no additional significant changes in weights and water content. This study has shown that X-rays induce stress in date palm seedlings, as evident by proline accumulation. A noticeable increase in weight and water content occurred without noticeable phenotypic changes. Ionizing irradiation technology can facilitate stress-related physiological studies. Further exploration of this technology may prove beneficial for genetic improvement strategies of date palm.