Abstract: In order to determine the effect of mycorrhizae in some macro and micro elements in water stress condition and different nitrogen rate. The experiment was carried out by using a randomized complete block design in 3 replications in 2008 in research and education station of Islamic azad university of firouzabad on corn KSC 704. The results showed that mycorrhizae increased significantly the absorbtion of nitrogen, phosphorous and potassium in shoot and in root too. Treatment of irrigation levels affected in 1% probability on absorbtion of all elements of nitrogen, phosphorous, zinc copper, iron and manganese with increase of water stress intensity nitrogen, phosphorous and manganese absorption was decreased. But potassium, iron, copper, zinc absorbtion was increased in similar water stress, mycorrhizae treatment showed an increasment in relative absorbtion of nitrogen, phosphorus, potassium, copper and zinc. With increase of nitrogen in mycorrhizae and nonmycorrhizae treatments absorbtion of nitrogen, phosphorous manganes and a little potassium increased but iron decreased and it has not any certain process about other elements.

INTRODUCTION

Water stress is one of the main problems of agriculture in arid and semiarid areas (Amerian et al., 2001). Since, water plays a very important role among environmental factors (Aliasgharzad et al., 2006). Lack of water influences on most of plant physiological processes such as photosynthesis, photosynthetic materials transmission to seeds, cleavage and cellular development, coalescence and transmission of nutrients in plants (Davis et al., 2007). Now, researchers can eliminate negative impacts of drought stress on crops someway, researchers gain a great accomplishment in the field of agriculture mycorrhizae fungi are able to moderate unpleasant impacts of drought stress in plants. They do that in many ways.

First, external mycelia of these fungi spreads in soil and penetrates small soil porosity in which there is no possibility for enter of hairs to absorb water and absorb it and transfer to the host plant (Avge et al., 1992; Davies et al., 1992). Second, they influence on the hormone surfaces of plant especially. ABA and cytokinin and stomatal conductivity (Druge and Schonbeck, 1993). Third, they influence on turger pressure and increas it through decreas of the leaf osmotic potential (Davies et al., 1993). One of the most important reasons of micorrhizae protection in drought stress conditions from the host plant is increase of nutrients absorbtion in soil and better feeding of plant (Johnson and Hummel, 1985). One of the most important elements absorbed by micorrhizae widly and actively is phosphore. The results of some research show that the speed of phosphore flow into micorrhizae plants (Jakobsen, 1995; Bolan, 1991; Sanders and Tinker, 1973). Inadditionto phosphore, nitrogen is one of elements whose absorbtion is increased by micorrhizae plants according to the research (Hamel and Smith, 1991; Caravaca et al., 2005). This absorption increase can be seen in mycorrhizae plants hypha have ability to absorb the soil nitrogen and transfer it to plants roots (George et al., 1992; Bago et al., 1996). Of course, it has been that fungi hyphe prefer nitrogen absorption of amunium kind to nitrate (Marschner and Dell, 1994; Barea et al., 1993).

Regading two elements sulfur abd boron, study results demonstrate that micorrhizae fungi do not have roles in sulfur transfer as much as phosphore (Cooper and Tinker, 1978; Shah et al., 2006). Reports about boron are contradictory but it is observed in mize that fungi have positive role in boron absorption increase (Kothari et al., 1991). The results demonstrate about elements potassium, calcium, magnesium and sodium that in some peinds of soil and plants and mycorrhizae of special types of fungi, there is absorption increase but in others, there is not an exact reaction or plant has not shown any reaction (Barea, 1992; Lembert et al., 1979). Most of studies regarding two elements zinc and copper comparing to non-micorrhizae plants (Gildon and Tinker, 1983; Swaminathan and Verma, 1979). Most of studies demonstrate an elimination of manganese absorption in micorrhizae plants (Arines et al., 1989; Kucey and Janzen, 1987). Some studies show absorption increase about iron in the presence of micorrhiza (Treeby, 1992; Raju et al., 1990a, b).

MATERIALS AND METHODS

This experiment was carried out in agricultural research college of Islamic Azad University of Firouzabad in 2008. The experiment was carried out besed on factorial design in randomized complete block design in 3 replication. Treatments were consisted of nitrogen fertilizers in amount of 150, 300 and 450 kg nitrogen from urea supply (46% nitrogen) and mycorrhizae treatment (M) consist of M1: inoculate whit mycorrhiza M0: not inoculate whit mycorrhizae and irrigation level consisted of:

In this exprement, 72 main pot and 15 sub pot for measuring moisture was used. Plant water necessity and amount of water required to plant is determined by measuring (fc) and (pwp) and soil (pb) and then available water was determined. Available water in fc condition was theorized 100. For appointment soil moisture sampling of sub pot each 2 days and then each sample was draied 24 h in 105°C in oven. For seedling inoculation used of propagol. Thus in each pot 3 hole stave and seedling and propagol dust in hole.

After seedling emergence only 1 seedling in pot was protect. Plant samples were sent to the laboratory instantaneously. They were clean thoroughly after being washed with ordinary and distilled water in the laboratory. Then they were dried in oven for 72 h and in 70°C and grinded afterwards. To measure nitrogen, 0.3 g of the plant sample were digested using sulphuric acid, salcilic acid and distilled water and then, its amount was specified with kejeldal. For other elements, 1 g of samples put in the electrical kiln in the temperature of 550°C for 5 h to become ash and then, it was digested with chloridric acid two normal. The elements were measured as follows:

The results were analysed after classification using the softwares; MINITAB and SPSS.

RESULTS AND DISCUSSION

The results demonstrated that the influence of nitrogen fertilizer, micorrhizae and irrigable areas on nitrogen absorption are significant in the level of 1% the irrigation areas impact in both micorrhizae and non-micorrhizae demonstrates a decreas in absorption of 2 elements phosphore and nitrogen. In maize as absorption stress increases. There was a difference and it was the mean average of absorption of these elements was higher in the micorrhizae and similar treatments which shows a positive impact of micorrhizae in absorbing these elements. Moreover, increasing the amount of nitrogen fertilizer, phosphor absorption increased in addition to nitrogen absorption. It was observed in both micorrhizae and non-micorrhizae plants but in micorrhizae plants, the amount of these 2 elements absorption was higher.

The reason why micorrhizae absorbs phosphore more quickly and violently is because of external mycelia scatetring of micorrhiza fungi in soil that eventfully enhances absorption level, mycelia are able to absorb phosphore from inaccessible areas of the plant roots and transfer it to the plant roots since, among all different ways of nutrients absorption, phosphore is absorbed through diffusion generally but in the presence of micorrhizae fungi, mycelia fungi are able to absorb these elements actively and consequently, phosphore absorption rath eliminates (Al-Karaki and Al-Raddad, 1997; Fomina et al., 2007).

Synergistic impacts between external mycelia of micorrhizae fungi and phosphate solvent bacteras which in this condition unavailable mineral phosphore transforms to available mineral phosphore transforms to available minral phosphore can increase. Usable phosphate for plant diffusion increase of H+ or hydoxidaz by hyphae (Marschner, 1991; Bolan, 1991; Isaac, 1992).

Increase of P absorption by micorrhizae plants hyphae may be because of increase of P absorbtion in the root length unit. This increased speed of absorption is 2-3 times more than non-micorrhizae plants (Tinker et al., 1992). Micorrhizae fungi discharge enzymes and materials in soil cansing transformation of unavailable organic phosphore to available one (Tarafdar and Classen, 1988; Tarafdar and Marshner, 1994; Nurlaeng et al., 1996) but many studies demonstrated that micorrhizae plants have higher phosphore absorption in the drought stress condition comparing to non-micorrhizae plants which has a harmony with this experiment results (Sieverding, 1983; Clark et al., 1999; Sieverding and Toro, 1988; Bethlenfalvay et al., 1987). In addition to phosphore absorption, the increase of nitrogen absorption in the micorrhizae plants has been frequently reported as well (George et al., 1995; Hamel and Smith, 1991).

The results of study on Cle demonstrate an increased nitrogen absorption of micorrhizae plants comparing to non-micorrhizae plants even when there is equal phosphore for them.

The results of studies on maize an in presence of micorrhizae fungi G. intraradieces demonstrate that more nitrogen has been absorbed by micorrhizae plants comparing to non-micorrhizae plants having access to not only non-organic resources (NH4)₂ So₄ but also organic resources of nitrogen. The results show that micorrhizae maize has used 17% and ordinary maize (non-micorrhizae) has used 5% of the nitrogen resources (Frey and Schuepp, 1993). Micorrhizae was sigmificant in potassium absorption in the level of 5% but the impact of irrigation areas and different amount of nitrogen was significant in the level of 1% (Table 1).

The results have also demonstrated an increased potassium absorption in both micorrhizae and non-micorrhizae plants as stress increased (Table 2). Also, increasing nitrogen, phosphor and kali absorption increased (Table 3). Other researchers report the micorrhizae impact on absorbing cations like K, Mg, Ca is contradictory so that somewhere increase of absorption, sometime decrease and sometime without impact has been reported (Azcon and Barea, 1992).

It seems the reasons of difference in results of these elements would be the type of soil (acidic or alkaline), soil Ph, the type of plant, the type of micorrhizae fungi, temperature but in maize root the impact of micorrhizae on nitrogen and phosphore absorption in the level of 1% became significant but regarding kali, it was significant in the level of 5%.

Table 1:	Mean square for the effect of water stress, different nitrogen rates and mycorrhizae on rate of absorbtion, nitrogen, phosphorus, potassium, iron, copper, zinc and manganese in shoot corn KSC 704
Ns, *, **Not significant, significant at the 5 and 1% levels of probability, respectively

Table 2:	Mean square for the effect of water stress, different nitrogen rates and mycorrhiza on rate of absorbtion, nitrogen, phosphorus, potassium in root corn KSC 704
Ns; *, **Not significant, significant at the 5 and 1% levels of probability, respectively

Table 3:	The effect of different irrigation levels on amount of absolution, nitrogen phosphorus, potassium, iron, copper, zinc and manganes in shoot corn mycorrhizae and non mycorrhizae KSC 704
Means followed by the same letter are not significantly different (Duncan 5%)

Table 4:	The effect of different irrigation levels on amount of absolution, nitrogen phosphorus, potassium, iron, copper, zinc and manganes in shoot corn mycorrhizae and non mycorrhizae KSC 704
Means followed by the same letter are not significantly different (Duncan 5%)

Also, the treatment impact of nitrogen on phosphore and nitrogen absorption become significant in the level of 1% but not about kali. The irrigantion areas were also significant on nitrogen and kali absorption in the level of 1% and on phosphore absorption in the level of 5% (Table 4).

Generally, the more stress, the less nitrogen and phosphore absorption in roots like shoot but kali absorption increases. Besides, nitrogen increase could enhance phosphore and kali absorption in plant (Table 5). Other researchers also believe that one of the impacts of nitrogen increase is the increase of cations absorption which is due to the increase of the plant metabolic activity, acceleration in most of processes and increas of the plant absorption power (Adeairan and Bonjorko, 1995; Staal et al., 1991).

But the impact of nitrogen treatment on absorbing micro elements like iron and manganese was significant in the level of 1% while its impact on copper and zinc was not saignificant. On the other hand, micorrhiza impact on copper and zinc was significant in the level of 1% but it was not significant on iron and manganese. The impact of irrigatition areas on these elements absorption become significant in the level of 1% (Table 1).

As stress increases in both micorrhizae and non-micorrhizae a plants; absorption of iron, copper and zinc increases but absorption of manganese dcreases (Table 3). Increasing nitorgen, absorption of manganese increases (Table 4). Many researchers declared micorrhizae increases zinc and copper absorption (Manjonath and Habte, 1988; Kucey and Janzen, 1987; Pacovsky et al., 1986).

In study on maize, it was observed that plant inoculation with micorrhizae could increase zinc absorption 48% comparing to treatment without micorrhizae (Kothari et al., 1991). Absorption increase of zinc and copper in the drought stressed plants but inoculated with micorrhizae has also been reported comparing to non-micorrhizae plants (Al-Karaki and Clark, 1998; Al-Karaki and Al-Raddad, 1997; Al-Karaki, 1998; Mohammad et al., 1995; Gao et al., 2007).

Table 5:	The effect of different irrigation levels on amount of absorption, nitrogen, phosphorus, potassium in root corn KSC 704 mycorrhizae and non mycorrhizae
Means followed by the same letter are not significantly different (Duncan 5%)

Moreover, many studies demonstrate the lack of iron an mangenese absorption increase in plants. On such condition, micorrhizae absorbs manganese and eliminates its toxicity in the plant.

Of course, the resutls are a little different in acidic and alkaline soil (Posta et al., 1994; Arines et al., 1989; Pacovsky, 1986; Ipsilantis and Sylvia, 2007). In this study, increase of nitrogen enhances manganese absorption but increase of manganes absorption; reduced iron absorption in the plant.

CONCLUSION

The results of this study clarifies properly that micorrhizae can increase absorption of some nutrients in plants in the drought stress conditions and moderate impacts of the stress. Most of these materails are elements having low motion power and less solubility in soil and drought stress conditions can restrict their absorption.