ANALYSIS OF THE PHOTOSYNTHETIC PARAMETERS, THE YIEL D AND THE QUALITY OF WINTER WHEAT

site of the University of Debrecen in small parcel experiments. We measured the leaf net CO2 assimilation rate, stomatal conductance, intercellular CO2 level, the transpiration, the leaf temperature and the air temperature by the LICOR LI-6400 portable photosynthesis system in field trials on the nutrient supply. The soil of the experimental area is calciferous chernozem with favorable water regime.


Introduction
Our research objectives were to determine the relationships between the nutrient supply, the photosynthetic parameters, yield quantity and quality of different winter wheat varieties via small-plots field trial on nutrient supply. From the external elements, the climatic conditions have the largest effect. We examined the photosynthesis of winter wheat at different nutrient supply in seven years.
Researchers studied the influencing factors of the photosynthesis system of the crops from different aspects. Bindraban (1999) found that the photosynthesis of wheat depends mainly on the light intensity and the effect of nitrogen supply is low. Vidal et al. (1996) estimated, that in consequence of the tripling the light intensity, the photosynthesis intensity was doubled. Shangguan et al. (2000), Futó (2003) agreed that the nitrogen and water supply have great effect on the photosynthetic gas exchange. The higher nitrogen supply lowered the water use efficiency of the plants and the net photosynthetic rate decreased. The effect of nitrogen nutrition on photosynthetic characteristics was not identical under different water status. Fernandez et al. (1996) monitoring physiological parameters (leaf water potential, leaf conductance and net photosynthesis rate) showed that water relationships of maize were not affected by the reduced N fertilization. Plant reproduction is sensitive to water deficits, and in maize the water deficits inhibit photosynthesis (Boyer-Westgate, 2004). Under N stress photosynthesis was reduced by a decreased light absorption and by the decreased utilization of assimilates (de Groot et al. 2003). Schmitt-Edwards (1981) data indicate that C4 species maize had greater nitrogen use efficiency than either the two C3 species examined. Csajbók et al. (2007) write that the differences between plant species in photosynthesis were significant but not in every cases. Changing the illumination intensity caused significant differences in the net photosynthesis rate. The CO2 assimilation of the maize was higher than potato or winter wheat above 500 mol photon m-2s-1 light intensity.

Materials and methods
The varieties belong to different ripening class under uniformed technology in 7 cropyears between 2001 and 2007. The observation was carried out at the Látókép Plant Cultivation Research Site of the Centre for Agricultural and Applied Economic Sciences, University of Debrecen.
The soil of the experimental area is calciferous chernozem. Its physical characteristics are that of semi compacted clay category. The thickness of the humus stratum is around 70-80 of which the evenly humidified stratum is about 40-50 cm thick. The humus content of the evenly humidified layer is 2.5-3.4 %. The soil specific plasticity index (KA) was 43, the pH value was nearly neutral (pHKCl=6.46). The phosphorus content of the soil was medium (the value of AL-soluble P 2 O 5 was 133 mg/kg), the degree of potassium supply was fairly-good (the value of AL-soluble K 2 O was 240 mg/kg).
Examining the water conditions of the soil, it can be stated, that it is typical to the chernozem soils, i.e. has favorable water regime, excellent water holding capacity (808 mm in the 0-200 cm layer), unavailable water content is 295 mm in the 0-200 cm layer, the amount of disponible water in saturated state is 513 mm in the 0-200 cm layer of which 342 is readily available. The watertable is at 8-10 meters depth.
The small-plot experiments were set up in split-plot arrangement with four repetitions. In each experimental year we applied the same fertilizer dosage. The forecrop was sweet corn in each year. The gross area of a parcel was 18 m2 in the split-plot design. In the experiment we have tested the following wheat varieties: GK Öthalom  Assimilation parameters were measured in the field with a LICOR 6400 portable photosynthesis system. We measured the leaf net CO 2 assimilation rate, stomatal conductance, intercellular CO 2 level, the transpiration, the leaf temperature and the air temperature, air pressure. Light changes will cause immediate photosynthetic rate changes therefore the light was controlled and stable in the sample chamber. We used 2000 µmol photon m -2 s -1 photosynthetic active radiation (PAR) with 90 % red (630 nm) and 10 % blue (470 nm) light. We measured six times per leaf, in four repetitions. The

Results and Discussion
Comparing the data of varieties, we can see that there are significant differences in the net photosynthesis rate between the varieties in all of the seven years with 5% error level. After data processing we found that there were significant differences on P=0.1% level in the net photosynthesis, the stomatal conductance and transpiration between the nutrient levels in every year. Figure 1 shows the effect of nutrient supply on the photosynthesis intensity.
The photosynthesis intensity of Mv Mazurka variety was remarkably higher than the others at better nutrient supply levels.
The maximum photosynthetic activity was detected at N 60 P 45 K 53 kg ha -1 in case of the four varieties ( Figure  1). The photosynthetic gas exchange parameters of wheat are remarkably improved by nutrient supply in well watered conditions. The water stress through decreased stomatal conductance has significant negative effect on the assimilation parameters.
The highest photosynthetic intensity we measured in 2005 and 2004 years ( Table 2). In these years was favorable weather conditions and the yield was the highest, but we did not find correlations between the yield and photosynthesis intensity except the GK Öthalom variety. According to the evaluation of the quality parameters it can be stated that the wet gluten content of Mv Mazurka was the highest on every fertilizer level in average, but it was only in 2006, 2007 in the experiment (Figure 3). There are no significant differences between GK Öthalom and Lupus in the Hagberg Falling Number, Mv Mazurka has the highest values (436-475 s) and the Fatima 2 the lowest (278-312 s).  Coming up to our expectations the fertilization has significant effect on the yield (r=0.81) and also the quality parameters (r=0.21-0.60). There was no correlation between the net photosynthesis rate and the fertilization level (r=-0.01) and was weak correlation between the transpiration rate and fertilization (r=0.28) (Figures 1-5).
Our measurements show strong connections between the measured quality parameters of winter wheat ( Table  3). There is very close, positive, significant correlation between the wet gluten contents and farinograph index (r=0.93), between the gluten elasticity values and farinograph index (r=0.92). There is close, positive, significant correlation between the wet gluten contents and the gluten elasticity values (r=0.85), between the wet gluten contents and the Hagberg Falling Number (r=0.85), between the farinograph index and the Hagberg Falling Number (r=0.76). There is medium positive correlation between the gluten elasticity values and the Hagberg Falling Number (r=0.64).
As we analyzed the correlations between the assimilation parameters and the yield and quality of wheat, we could see that there is no correlation between net photosynthesis rate and yield (r=-0.03), but there is medium, positive, significant correlations between the transpiration level and the yield (r=0.66).
There are medium to close correlations between the net photosynthesis rate and the quality parameters. There is close, positive, significant correlation between net photosynthesis rate and the Hagberg Falling Number (r=0.78). There are medium, positive, significant correlations between the net photosynthesis rate and the wet gluten contents (r=0.69) the farinograph index (r=0.51), and the gluten elasticity values (r=0.54).
Between the transpiration values and the Hagberg Falling Number there is negative medium correlation (r=-0.58). That means, that the better water conditions could cause higher enzyme activity and lower falling number in winter wheat-as show the results of our experiments.

Conclusions
The results show that there are significant differences in the net photosynthesis rate, the stomatal conductance and transpiration between the varieties and can be found significant differences also between the nutrient levels in every year.
Our measurements show strong connections between the measured quality parameters of winter wheat varieties.
Medium to close correlations can be found between the net photosynthesis rate and the quality parameters in the analyzed years.