The Response Of Winter Wheat Root Growth To Different Irrigation Conditions

Wheat is one of human's major food crops, however, 70% of the wheat plants in arid and semi-arid areas. In these areas, water shortage is an constraint factor to wheat's yield. Therefore, research on how to use the limited water resources efficiently and increase the yield is the most critical problems of the agricultural in arid and semi-arid areas. The physical and ecological responses differences are result from the winter wheat's varieties differences under different irrigation conditions. Meanwhile, root is the most important factor on determining the drought resistance and yield. Hence, study on the response of winter wheat root growth under different irrigation conditions is the key content of the research of agricultural science and technology in arid and semi-arid areas.In this paper, the experiment was carried by using T.dicoccon Schuebl (original variety), T.aestivum L Xinong9871 (sensitive modern wheat) and T.aestivu L Changwu 134 (drought-resistant modern varieties) under the large shed and the open field at Chinese Academy of Sciences&Ministry of Water Resources. Research on the growth, yield and photosynthetic parameters of the winter wheat underground and on the ground in different irrigation conditions, the results are as follows.1. Irrigation conditions affect root growth of winter wheat significantly. In harvest time, under no irrigation treatment, the root dry weight of T. dicoccon Schuebl, T.aestivum L Xinong9871 and T. aestivu L Changwu134 are 210.2kg/hm2, 204.4kg/hm2 and 196.2kg/hm2. Compared with no irrigation treatment, irrigation treatment can increase the root weight obviously. Among different irrigation treatments, one irrigation treatment reaches the maximal root dry weight improvement and the increased extents are 97%, 75% and 195%. Compared with sufficient water treatment, one irrigation treatment and two irrigation treatments both increase the root dry weight of T.aestivum L Xinong9871 and T. aestivu L Changwu134. The root dry weight increased 33.2kg/hm2 and 181.6kg/hm2 under one irrigation treatment, and the root dry weight respectively increased 14.3kg/hm2 and 85.8kg/hm2 under two irrigation treatments, respectively. Meanwhile, the irrigation treatments can change the root distribution, too. Compared with sufficient water, one irrigation treatment, two irrigation treatments and three irrigation treatments all have increased proportion of root length density and root surface area in the 0～60cm soil layer and have decreased which bellow 60cm soil layer. This limits the root to grow deeper and to absorb the deep soil water. However, one irrigation treatment increases the proportion of root length density and root surface area in 130～180cm soil layer of T. dicoccon Schuebl and T. aestivu L Changwu134, which benefit them to resistance drought.2. Irrigation treatments impact on the growth and water use efficiency of winter wheat on aerial part. The peak of tillering of T.aestivum L Xinong9871, T. aestivu L Changwu134 appeared in the jointing stage under sufficient water treatment, but which appeared in the green stage green under no irrigation treatment, one irrigation treatment. Compared with sufficient water treatment, one irrigation treatment and no irrigation treatment improved winter wheat's water use efficiency, which is because the increase extent of yield is greater than water consumption under one irrigation treatment and the decrease of water consumption under no irrigation.3. The irrigation treatments impact on the winter wheat's photosynthesis and PEPCase activity. Under no irrigation treatment, one irrigation treatment, two irrigation treatments, the photosynthetic rate, transpiration rate, PEPCase activity in the jointing stage and the flowering period were higher than under sufficient irrigation treatment. But in the harvest time, compared with sufficient water treatment, the winter wheat's photosynthetic rate, transpiration rate, PEPCase activity were dropped significantly, which is because the soil was dry for a long time under no irrigation treatment and one irrigation treatment. Therefore, the research results show that moderate water deficit that can increase the winter wheat's photosynthetic rate, transpiration rate and PEPCase activity, which can improve the drought resistance of the winter wheat.4. The response of irrigation treatments were differences among varieties. Under sufficient water treatment, the order of root weight in harvest time was: T. dicoccon Schuebl > T. aestivu L Changwu134> T.aestivum L Xinong9871. Under no irrigation and one irrigation treatment the order of root weight was: T. aestivu L Changwu134> T.aestivum L Xinong9871> T. dicoccon Schuebl. Compared with sufficient water treatment, the decrease ranges of root weight about T. dicoccon Schuebl, T.aestivum L Xinong9871, T. aestivu L Changwu134 have significant differences, and the significant differences of these three varieties are 70.3%,50.6% and 36.9%. These mean that the original variety is much easier impacted by water condition than modern variety and sensitive modern wheat is easier impacted by water condition than drought-resistant modern varieties. Besides, the impact of irrigation treatments on root distribution also differences among varieties. Under one irrigation treatment, the root weight of T. dicoccon Schuebl was increased in 0～60cm soil layer and but decreased bellow 60cm soil layer. However, the root weight about T.aestivum L Xinong9871 in 90~140cm soil layer and T. aestivu L Changwu134 below 150cm soil layers were increased, which can benefit the root absorption of soil water of deep layers and meanwhile increase drought resistance of modern varieties. Irrigation impact on growth and development of aerial part were differences among varieties. Under no irrigation treatment, one irrigation treatment and sufficient water irrigation treatment, the plant height and biomass of T. dicoccon Schuebl were significantly higher than T.aestivum L Xinong9871 and and T. aestivu L Changwu134, indicating that the growth of T. dicoccon Schuebl was better than T.aestivum L Xinong9871 and and T. aestivu L Changwu134. But the grain number per spike was significantly lower than T.aestivum L Xinong9871 and and T. aestivu L Changwu134, yield and harvest index was only half of T.aestivum L Xinong9871 and and T. aestivu L Changwu134, which shows the high-yielding characteristics of modern varieties. In addition, the transpiration rate of T.aestivum L Xinong9871 was greater than T. aestivum L Changwu134 under the sufficient, which means that under sufficient water situation, water sensitive varieties's transpiration rate is higher; however,under one irrigation and no irrigation treatment the transpiration rate of T. aestivum L Changwu134 is higher than T. dicoccon Schuebl and T.aestivum L Xinong9871. Therefore, it can be concluded that drought-resistant modern varieties's transpiration rate is higher than other varieties under water shortage condition.