Effects Of Water Deficit On Photorespiration And Glycolateoxidase Activity In Wheat

In recent years, with the further research on photo-respiratory metabolism, reducing thephotorespiration rate of plant’s green organs has been developed to be an important process to“high efficiency photosynthetic for breeding”. Currently, the main determination methods ofphotorespiration rate include Gas exchange by subtraction （P_Δ）, P_n-C_i Response curvemethod (P_curve) and Rubisco Dynamics combined with gas exchange law (P_model). Theseprocesses all indicate theoretical drawbacks and operational disadvantages to some extent. Atpresent, these three methods are usually combined together when applied and utilized in thedetection process, while the comparisons and studies among these methods are rarelyreported. In this study, the research with the three methods above is carried aboutinvestigating the respiratory characteristics of varieties of wheat under different watertreatments, as well as the difference among individual method. A better method can beobserved as the optimal process to determine the photorespiration rate. Based on the studiesabove, discussion and analysis are brought out about the influence of water content on dailyphotorespiration of flag leaf and ear of wheat, dynamic change of photorespiration in fillingstage and the activity of the key photorespiration enzyme, which providing directions torelevant research on wheat photorespiration. The primary achievement showed as followed:1. At the anthesis of wheat, the three methods, P_Δ、P_curveand P_model,detected thephotorespiration rate （P_r） of flag leaf and the ratio （P_r/P_n） of photorespiration rate tophotosynthetic rate, with the samples of different varieties of wheat and water treatments. Theresults of P_rand P_r/P_ngetting by P_Δand P_curveindicate differences is not significant （P>0.05）;on the contrary, the result of P_rand P_r/P_ngetting by P_modelindicates significant differences（P>0.05）. In the test, the P_rgetting by P_Δand P_curveis the total CO₂released fromphotorespiration and mitochondrial dark-respiration, which is greater than true values,therefore P_rand P_r/P_nobtaining by P_Δand P_curveare both larger than the results obtaining byP_model.This experiment indicates that P_modelis more precise than P_Δand P_curve, in addition tothe simple operation and common instrument of P_model, which provide much convenience tothe detection of photorespiration of wheat‘s flag leaf and other organs. 2. At the anthesis of wheat, the changes of daily photorespiration of flag leaf and ear ofwheat, Qin Mai3（drought-resistance） and Shaan229（water-sensitive） under two kinds ofwater treatment, both display as unimodal curves, while the peak value of curves exitdifference. With the normal water supply, the peak values of two varied flag leaf’sphotorespiration and ear of wheat’s photorespiration appear at14:00and12:00, respectively.With the middle water force, the peak values of ear of wheat’s photorespiration move to12:00, however the peak value of Shaan229flag leaf’s photorespiration moves to10:00, theQin Mai3appears no modification. This experiment indicates that wheat may decrease thedamage causing by excess light to its photosynthetic organs through improving itsphotorespiration in the hardship time, and the result proves the viewpoint that plants takeadvantage of photorespiration as a kind of protecting mechanism in the adverse situation.3. After the anthesis of wheat for0d,7d,14d,21d separately, the photorespiration ratesof flag leaf and ear of wheat, Qin Mai3（drought-resistance） and Shaan229（water-sensitive）under two kinds of water treatments, both perform a downward trend. In the same period afterblooming, the photorespiration rates of flag leaf and ear of wheat, two varied wheat undermiddle water force treatment, are both higher than original ones, increasing by33.5%and30.2%, respectively. This experiment reveals that the photorespiration rate of wheat may goup under water force treatment. The gradually declined photorespiration rate of wheat duringthe filling stage is mainly due to the decay of photosynthetic organs.4. After the anthesis of wheat for14d, the activities of Glycolate Oxidase （GLO）containing in the flag leaf and ear of wheat, Qin Mai3（drought-resistance） and Shaan229（water-sensitive） under middle water force treatment, increase by42.3%and5.9%,46.8%and10.7%, separately. Nevertheless, the activities of Glutamine Synthetase （GS） containingin the flag leaf and ear of wheat, Qin Mai3（drought-resistance） and Shaan229（water-sensitive） under middle water force treatment, decrease by16.1%and24.0%,22.5%and27.6%, separately. The results reveal that the responses of GLO and photorespiration to waterdeficit are similar, the relevance is positive; the responses of GS and photorespiration towater deficit are opposite, the relevance is negative.