الفهرس 
AbstractOnly 14 pages are availabe for public view
 |  | from | 161 |  |  |
| | | from | 161 | | |
Abstract
Salinity stress is one of the most serious environmental stress factors restraining crop productivity, in Egypt and worldwide, causes reduction of global income. Hence, the aim of this work was to introduce a low cost, efficient and environmentally friend solution for the problem of salinityusimg maize plant.
The present investigation was conducted under the prevailing natural conditions in an opened field. In this experiment, seeds of maize plant (Zea mays) were primed by soaking in 0.0, 1 and 3% (w/v) aqueous Echinochloa waste extract (EAAE) for 24h then irrigated with tap water up to 7 days. The seeds were divided to three subgroups which irrigated with distilled water, 100 mM NaCl and 200 mM NaCl up to 15 days to investigate the potential effects of EAAE.
The obtained results can be summarized as the follows:
1- All investigated growth criteria [root length (RL), shoot length (SL), shoot:root ratio (S:R ratio), fresh weight (FWt.), dry weight (DWt.), water content percent (WC%), relative water content (RWC) and leaf area (LA)] were retarded by salinity stress and high concentration of EAAE, while application of low concentration of EAAE alleviated the negative effects of salinity stress and improved all measured growth parameters.
2- Photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoids) were non-significantly changed by salinity, while application of low concentration of EAAE significantly increased them in absence of salinity, consequently alleviate the effect of salt stress on such pibments. The high concentration of EAAE significantly reduced the content of photosynthetic pigments in absence or presence of salinity.
3- Total soluble sugars content was increased by salinity stress and. Also application of low concentration of EAAE alone or in combination with salinity stress enhanced itthis content, while application of high concentration of EAAE significantly reversed that matter.
4- Proline, total amino acids and lipid peroxidation (MDA) contents were increased upon salinity application. Also treatment with low concentration of EAAE significantly increased their content in absence of salinity as well as under salt stress. On the other hand, high concentration of EAAE increased their content under stressful conditions, while their content was decreased under non-stressful conditions.
5- Antioxidant enzymes [catalase (CAT), peroxidase (POX), superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione peroxidase (GPX)] showed high activities under salinity. Application of low concentration of EAAE enhanced the activity of these enzymes either in stressed or non-stressed plants. Also high concentration of EAAE showed stimulatory effect on them under salt stress, while the activity of these enzymes was decreased under non-stressful conditions.
6- Salt stress had non-significant effect on the content of K+ and induced increase the content of Na+. On other hand it decreased the content of total phosphorus and total nitrogen. The application of low concentration of EAAE reduced the content of K+ in absence of salinity, while it increased K+ content under salt stress. The same treatment mitigated the loss in N and P under salinity, while it mitigated the accumulation of Na+ at low salinity and increased it at high salt stress.
Generally, the alleviating role of the application of EAAE may be attributed to its role in the hormonal regulation, osmotic regulation and antioxidants biosynthesis. This positive role of EAAE may be summarized as below:
1- EAAE causing enhancement of the plant nutrient status especially of K, P, N and K+:Na+ratio, which reduces the sodium accumulation due to salinity stress, and enhances plant growth and various metabolic processes like photosynthesis, amino acid, proline and total soluble sugars.
2- The containing of EAAE with phenolics, like ferulic acid and cinnamic acid which caused activation of the antioxidant system including non-enzymatic antioxidants (such as AsA and GSH) and enzymatic antioxidant including (CAT, POX, SOD, APX and GPX), and hence, enhances the free radical scavenging process.
Finally, this work recommends soaking maize seeds in EAAE before cultivation to improve its growth, either under normal condition or under salt stress.