Studies On The Photosynthetic Characteristics Of Warm-season Turfgrasses

Many photosynthetic characteristics of Zoysia sinica,Cynodon dactylon,Eremochloa ophiuroide,Paspalum notatum were studied,such as diurnal and seasonal changes in net photosynthetic rate (Pn),the effects of the environmental factors on diurnal and seasonal changes in Pn,the effects of photosynthetic active radiation, CO2 concentration on photosynthesis,the anatomical characteristics by full daylight and shading treatment in HuNan Province. Some significant results have obtained as the followings:1, light, temperature, humidity and CO2 concentration is the warm-season turfgrasses photosynthesis important environmental conditions, four warm-season turfgrasses in Hunan in the photosynthetic rate (Pn), similar types of changes are typical of "bimodal"--each of the morning and afternoon has a peak, and noon with a "Dormancy" phenomenon, and the "Dormancy" for different reasons, resulting in the Zoysiasinca"Dormancy" in the non-stomatal limitation reasons, and three other warm-season turfgrass species of photosynthetic "Dormancy" due mainly to the stomatal limitation.2, Paspalum notatum's photosynthetic rate of seasonal changes in the "bimodal" trend, the other three warm-season turfgrass photosynthetic rate changes in the "single-peak" trend. The difference between photosynthetic rate of warm-season turfgrasses in different seasons may reflect in the temperature of different grasses demand. In summer, Cynodon dactylon and Paspalum notatum's photosynthetic rate higher at 48.3 and 50 umol CO2·m-2·s-1 This result showed that Cynodon dactylon and Paspalum notatum requirements of the higher temperatures than Zoysia sinicaand Eremochloa ophiuroide, and at spring and autumn while Paspalum notatum's photosynthetic rate higher, thus Paspalum notatum's growing period is longer than the other three warm-season turfgrasses. In Spring, Zoysia sinica, Cynodon dactylon and Eremochloa ophiuroide has the low photosynthetic rates were 18.1,14.6 and 12.8 umol CO2·m-2·s-1 that they required regreening of the temperature higher than Paspalum notatum.3, Zoysia sinica's LSP and the LCP is 1181.25 and 46.40μmol·-2-s-1, Cynodon dactylon is 1285.71 and 67.14μmol·m-2·s-1, Eremochloa ophiuroide's is 1375 and 46.25μmol·m-2·s-1, Paspalum notatum's is 1306.25 and 27.5μmol·m-2·s-1. Paspalum notatum's light compensation point minimum on their ability to adapt to the low light of the strongest; Eremochloa ophiuroide's LSP maximum on its ability to adapt to the glare of the strongest. of the strongest. Paspalum notatum's AQY is the highest as 0.0257 molCO2mol-1, it showed that Paspalum notatum has the most efficient use of energy, Eremochloa ophiuroide's AQY is the lowest as 0.0165 molCO2mol-1, it showed that Eremochloa ophiuroide has the inefficient use of low-light. Potential of photosynthetic for the sort Paspalum notatum> Cynodon dactylon> Zoysia sinica> Eremochloa ophiuroide.4, Warm-season turf grasses have lower CCP and higher CSP, and the warm-season turfgrasses on high CO2 concentrations and low concentrations of CO2 are highly adaptive capacity, the ability to make use of CO2 strong.Four warm-season turfgrasses'CCP for the Zoysia sinicamaximum 29.44μl·L-1, Paspalum notatum 23.23μl·-1, Eremochloa ophiuroide 21.91μl·*L-1, Cynodon dactylon 10.91μl·L-1.In four warm-season turfgrasses, Paspalum notatum CO2 saturation point maximum to 1870μl·'L-1, followed by bermudagrass, CCP for the 1810μl·'L-1, followed by Zoysia sinica, and its value is 1707.14μl·L-1, the lowest is Eremochloa ophiuroide, and its value is 1520μl·L-1 These results showed that Paspalum notatum its high concentration of CO2 adaptive capacity and ability to make use of more than Cynodon dactylon and Eremochloa ophiuroide, and Cynodon dactylon has strongest ability on that to make use of low concentration of CO2; the scope of the use of CO2 is different of four warm-season turfgrasses. Paspalum notatum has the most wide scope of the use of CO2, the second is Cynodon dactylon, and then the Zoysia sinica, Eremochloa ophiuroide has the narrowest scope.5, The shading treatment Changed the diurnal variation trend of net photosynthetic rate of four warm-season turfgrasses. the diurnal variation trend of Pn of four warm-season turfgrasses was obviously a "single peak" and in a variety of shading, four warm-season turfgrasses annual average photosynthetic rate was lower than the control levels, but the peak of Pn in one year with the control both appeared in September, the shade will reduce the warm-season turfgrass growth rate, but it will not change its growth rhythm.6, The chla/chlb of shade-tolerant plants can be used as indicators, under 50%of shading, chla/chlb value for the sort of Eremochloa ophiuroide> Paspalum notatum> Zoysia sinica>Cynodon dactylon, under 70%of shading,it sort of Cynodon dactylon> Eremochloa ophiuroide> Zoysia sinica> Paspalum notatum, under 90%of shading, chla/ chlb value for the sort of Eremochloa ophiuroide> Cynodon dactylon> Zoysia sinica> Paspalum notatum. The results showed that:Eremochloa ophiuroide in various degrees of shade conditions are relatively adaptation of the performance of the Zoysia sinica; Paspalum notatum performance better at a lower intensity of shading, but can not adopted the higher intensity of shading; Cynodon dactylon in the low intensity of the shade under the worst performers, but in the high intensity shade the performed better.7, The anatomical structure four warm-season turfgrasses'leaves have shown a typical "C4 plants" features. Four warm-season turfgrasses leaves bundle sheath, or followed a nearly circular ring in the order of mesophyll cells, forming a "rosette" structure, the structure help CO2 to reuse and improve the photosynthetic efficiency, it is a typical structure of C4 plants. But four warm-season turfgrasses leaves in various parts of the structure are more obvious differences. In the 50% shade conditions, the warm-season turfgrasses leaves anatomical structure did not change significantly; in the 70% and 90% of the shade conditions, four warm-season turfgrasses leaf morphology have shown for the strip, the thickness of thin wall organizations increased, and assimilation cells decrease in the number of cells increasing gap leaves close of the organizational structure (CTR),and a series of characteristics of life-shade leaf.