Sowing at suitable time, there were differences in both canopy photosynthesis and grain yield of winter wheat (cv. Lumai No.5) at the following plant densities: 8×10~4, 16× 10~4and 24×10~4seedlings per mu.

The trend of root population absorption vigour(RPAV) and canopy apparent photo-synthetic rate(CAPR) and the relationships between them on winter wheat (variety: Lumai 14) which was planted on pondlets were studied by using isotope tracer and canopy photosynthesis measurement techniques.

Mathematically Modeling of Ecophysiological Process Response to Environmental Factors for American Black Walnut Seedlings(Ⅲ):The Mathematical Models of the Canopy Photosynthesis

Results of the numerical simulation show that (1)on a fine day,the canopy photosynthesis increases with CO_2 enhancement,and the daily total photosynthesis will increase by 19.7% when the CO_2 concentration increases from 330×10~(-6) to 660×10~(-6);

The simulation result by using the model indicated that: (a) When the concentration of O 3 increased from 0 ×10 -9V/V to 200 ×10 -9V/V, the canopy photosynthesis will decrease about 29% in contrast with the base value.

(2)the canopy photosynthesis increases with radiation enhancement,and the daily total photosynthesis will increase by 6.7% when the radiation increases by 10.0%;

(3)the canopy photosynthesis decreases with temperature increasing,and the daily total photosynthesis will decrease by about 2.9% when the temperature increases 1 ℃.

Soil respiration and net canopy photosynthesis were both increased by added N and elevated CO2, but soil respiration increased proportionately less than fixation by photosynthesis.

Soil respiration and net canopy photosynthesis were both increased by added N and elevated CO2, but soil respiration increased proportionately less than fixation by photosynthesis.

Daily rates of canopy photosynthesis (PcD) as well as the optimal leaf area production per unit nLat which PcDfor a given total amount of nitrogen in the canopy (i.e., canopy-PNUE) is maximized were also calculated.

Despite a decrease in leaf area index and total nitrogen available for photosynthesis in the flowering stand, the leaf nitrogen distribution here also leads to an almost maximum canopy photosynthesis.

We studied both the effect of nitrogen reallocation and leaf shedding on the whole canopy photosynthesis and changes in leaf nitrogen distributions in stands moving from the growing to the flowering stage.

Supposing that adaptation of leaf to enironmental light conditions brings about moreefficient use of limited nitrogen resource by plantcanopy, by using the method of variationalcalculus, optimal vertical distribution of leafphotosynthetic capacity with cumulative LAIas the vertical axis has been analysed. Whenleaf photosynthetic capacity distribution runsparallel to. that of light intensity, canopy pho-tosynthetic rate and in turn nitrogen use effici-ency will be the highest. The comparison be-tween canopy photosynthetic...

Supposing that adaptation of leaf to enironmental light conditions brings about moreefficient use of limited nitrogen resource by plantcanopy, by using the method of variationalcalculus, optimal vertical distribution of leafphotosynthetic capacity with cumulative LAIas the vertical axis has been analysed. Whenleaf photosynthetic capacity distribution runsparallel to. that of light intensity, canopy pho-tosynthetic rate and in turn nitrogen use effici-ency will be the highest. The comparison be-tween canopy photosynthetic rates of canopiesand different leaf photosynthetic capacity dis-tribution patterns shows that the one with de-creasing distribution will have higher canopynitrogen use efficiecy, and that the advantageof such adaptation to light would be greaterin canopy with higher extinction coefficient andLAI. Under certain conditions, daily photo-synthetic rates of the canopy with the optimalleaf photosynthetic capacity distribution havebeen calculated to be 11.7% and 36.5% hi-gher than those wi uniform distribution when extinction coefficients are 0.4 and 1, respecti-vely. Furthermore, a model of photosynthe-sis of canopy with optimal leaf photosyntheticcapacity distribution has been derived. Inthe new model, because of leaf adaptation, the rate of canopy photosynthesis will neverdecrease with an increase in LAI and will belinearly proportional to the fraction or totalamount of radiation intercepted. The de-pendence of canopy light use efficiency on can-opy structure and leaf photosynthetic chara-teristics has been demonstrated.

Experiment results showed that the change in the canopy respiration rate (CRR) of winter wheat was a single peak curve through the whole growth period. Maximum values of CRR occurred before or after the anthesis stage. The value of CRR was greater and the maximum value emerges earlier and decreases faster in the high density population than in the low density population. Daily changes of CRR were affected by temperature. The ratio of CRR to the canopy photosynthesis rate (CPR) varies in accordance with...

Experiment results showed that the change in the canopy respiration rate (CRR) of winter wheat was a single peak curve through the whole growth period. Maximum values of CRR occurred before or after the anthesis stage. The value of CRR was greater and the maximum value emerges earlier and decreases faster in the high density population than in the low density population. Daily changes of CRR were affected by temperature. The ratio of CRR to the canopy photosynthesis rate (CPR) varies in accordance with the growth stage, variety and density. The jointing-booting and the middle-period filling-maturing periods are two high ratio periods. The mean value of CRR/CPR in the whole growth stage is 31.4%.The CRR/CPR ratio of the low density population is lower than the high density population. The number of tillers per mu, the leaf area index and the dry matter weight exhibited a significant correlation with CRR before the booting stage. The correlation of CRR with yield was positive but not significant. Decreases in the number of basic seedlings could decrease the CRR/CPR ratio, and are favourable to grain yield increases.

This study was carried out to relate directly the ND index of spec- tral reflectivity to crop canopy photosynthetic activity in winter wheat. It was found that,ND index was highly and positively correlated with the canopy photosynthesis,i.e.,ND value increased with the increase of canopy photosynthetic activity (r>0.01);whilst there was no significant correlation between ND index and LAI (—0.14canopy photosynthesfs,different...

This study was carried out to relate directly the ND index of spec- tral reflectivity to crop canopy photosynthetic activity in winter wheat. It was found that,ND index was highly and positively correlated with the canopy photosynthesis,i.e.,ND value increased with the increase of canopy photosynthetic activity (r>0.01);whilst there was no significant correlation between ND index and LAI (—0.14canopy photosynthesfs,different from that revealed by LAI.Moreover it was shown that the ND value changed parabolieally with the pro- gess of wheat growth,and increased with the increase of yield.As a result,in the study of wheat population structure,it would be superior to indicate the canopy photosynthtic efficiency by MSS spectral reflec- tivity over to show the canopy structure by LAI.