Studies On Water Use Efficiency And Adaptability Of Black Locust Clones

In this paper, they were studied the dynamic variation of the water consumption, water consumption rate (WCR), air exchange, Water Use Efficiency (WUE), δ¹³C .Isotope discrimination(â–³) as well as the relation between δ¹³C and the Instantaneous WUE of Black locust clones by means of the simulated method in glasshouse. Meanwhile the relationship between the growth of Black locust clone and environment condition also had been studied. The objective of the study is to provide a theoretic basis for selecting good quality Black locust clones with low water consumption, high Water Use Efficiency and high resistance to adverse environment which suit for the purpose of afforestation in arid and semi-arid area.The result of the study show that the diurnal courses of water consumption and WCR of seedlings of Black locust clones appear "Single Peak" pattern (but 8041 appearing "Double Peaks) clearly under normal water condition. The daily highest water consumption and WCR emerged in the period of 12:00～14:00. The water consumption per hour during this period account for 13% of that of the whole day, and 14% of the daytime. The largest WCR was about 1.7 times as much as the average in daytime. The water consumption in daytime shared for 90～95% of that in whole day, and in night with 5～10% . There was some difference about the water consumption among different clones, the water consumption of U2,U5,U7,U9,NC and 8041 in whole day are as follow: 0.27,0.29, 0.30, 0.29,0.23 and 0.26kg respectively, of which U7 is the largest, and NC is the lowest. Under medium water deficit condition, the water consumption reduce 35⁵0%, and reduce 80⁹0% under intensive water stress condition. Of which, U5 is the most drought resistance clone with the largest water consumption decreasing of 47.95% and 88.34% under medium and intensive water stress respectively, and NC is the most no drought resistance clone with the least water consumption decreasing of 0.48% and 80.19% under medium and intensive water stress respectively,There is some difference about the photosynthesis rates and WUE among different Black locust clones. For the annual mean Pn,U7 (10.82 μmolH₂Om^-2s^-1) and U9 (10.81 μmolH₂Om^-2s^-1) are the highest, 3002 (6.90 μmolH₂Om^-2s^-1) and NC (7.69 μmolH₂Om^-2s^-1) are the lowest; for WUE, U9 (2.07 μmolCO₂/mmol ) and U2 (2.02 μmolCO₂/mmolHO₂ ) are the highest, and 8043 (1.70 μmolCO₂/mmolHO₂)are the lowest. U7 with high Pn and Tr is high productivity and water consumption clone, and suitable for developing in abundance rainfall area. U9 is a clone with high Pn and low Tr, it possesses a very high productivity and save water, so it is a primary choice in Black locust afforestation. WUEs of U2 and 8041 are also very high, but its Pn and productivity are low relatively, and not suitable for development in afforestation.The water stress caused Pn and Tr reduced continuously. The medium water stress led to WUE increased, but reduced by intensive water stress. Under medium water stress condition, WUE of U5 and U9 increase 211% and 244% respectively, they have a relatively high resistance to the drought, and that of NC and U7 just increase 76% and 99% respectively, their resistances to drought are poor relatively. The most optimal soil moisture contents for photosynthesis of clone U5,U9,8041,NC, 8048, 3-1, Daye and Xiaoye are as follow: 17.13%, 17.38%, 16.87%, 17.37%, 16.92%, 17.20%, 16.98% and 17.42%, and the fitting range are: 7.75,10.42,6.83,8.40,7.53,11.53,8.02 and 7.88 % respectively. The most optimal soil moisture contents for transpiration of U5,U9,8041,NC,8048,3-I,Daye and Xiaoye are as follow: 17.23%, 17.61%, 16.96%, 17.44%, 17.20%, 17.70%, 17.15% and 17.64%, and the fitting range are: 7.55,11.06,7.74,8.53,10.92,11.93,8.48 å’Œ 8.71%. For all clones, the most optimal soil moisture contents for photosynthesis are higher than that of transpiration, that is the reason why medium water stress promote WUE rising. On the base of the fitting soil moisture ranges for photosynthesis and transpiration, 3-I has a high resistance to drought and more widen adaptability to soil water environment. But 8041 has a poor resistance to drought and more narrow adaptability to soil water environment.Under water-welled condition, δ¹³C_foliar of U5, U7, U9, 8041, NC, 8048, Daye, Xiaoye and 3-I are: -29.232‰, -29.055‰, -29.059‰, -29.772‰, -30.068‰, -29.241‰, -30.257‰, -29.849‰ and -29.351‰, U7 and U9 are the highest, and NC is the lowest, the sequence is nearly same as that of instantaneous WUE. It is show the linear relation between the instantaneous WUE and δ¹³C_foliar, and the instantaneous WUE would increase with the rising of δ¹³C_foliar. It is show the negative relation betweenWCR and δ¹³C, WCR would decrease with the rising δ¹³C_foliar.According to the adaptability of clones to site condition in West Henan hill area, the clones fall into four categories, viz. â‘  The optimal suitable clones, including: 8041, 8062, 2F, G1, Jing24, 84023 and 8048 etc. 7 clones; â‘¡ The suitable clones, including: 3-I, G, X5, Jiangan, 83002, A05 and Lu10 etc. 7 clones; â‘¢ Inferior suitable clones, including: Jing13, R7, L5, Jing1 and R5 etc.5 clones; and â‘£ 8042 is the most inadaptable clone. The clones with high δ¹³C show a good adaptability to this area. The annual growth rate is inversely proportional to the stand age and annual cumulative temperature, and is negative proportional to sunshine hours and rainfall during winter and spring. Of which annual cumulative temperature is the main climate factor which possess a largest effect on the growth of Black locust, and the rainfall during winter and spring also has a very important impact on the growth. The clones with good performance always have more high resistance to drought, δ¹³C and WUE, and the clones with poor performance always have lower resistance, δ¹³C and WUE.