| Cabernet Sauvignon is the main wine-making variety in the whole wide world.Its germination time is late,and shoots shriveling often occurs in the northern region of China.In this study,in order to find out the reasons of shoots shriveling in Cabernet Sauvignon’s,the free and irreducible water content in shoots,cortical pore structure,water supply ability of roots,and respiratory metabolic dynamics in roots and shoots were analyzed.The results suggested that the big cortical pore,quick loss of water in shoots,the late activity of respiration in roots,and the delayed water supply of roots were the main reasons.Based on the above reasons,to reduce the occurrence of shoots shriveling,the roots were covered tent,that could not only increase the ground temperature and promote water absorption and supply in roots,but also supplement water in the shoots.The main results are as follows:(1)The shoots of grape varieties with different germination time were collected to explore the water content and cortical pore structure,including Cabernet Sauvignon,Chancelo,Vidal,Zexiang,Moldova,Fork,and 101-14 M.The results showed that the trend of water content in shoots showed a ’single peak’ curve through the over-wintering period,and decline sharply after reaching the peak.The minimum water content in Cabernet Sauvignon shoots were significantly lower than the other varieties,reaching 39.48%,and the water loss speed in Cabernet Sauvignon shoots was the fastest.On the other side,the pores number per unit area in Cabernet Sauvignon was the largest,especially the number of maximum and medium pores is significantly more than the other varieties.These results suggested that the larger number and area of pores were the main reasons for the quickly water loss speed.(2)Taking Cabernet Sauvignon trees of the same age as well as trees of the species Early Kyoho that are not easy to be shoots shriveled,the time of root water and stem flow were analyzed.The results showed that the peak time of the aboveground stem flow of Cabernet Sauvignon was 30 d later than that of the Early Kyoho peak,and the peak time of the root water was 32 d later.The root water supply delay is one of the causes of Cabernet Sauvignon shoots shriveling.(3)The results showed that the peak time of the total respiratory intensity in the bud of Cabernet Sauvignon was significantly earlier than that of the root system,the difference was12 days,and the peak time of the bud and the root system of Early Kyoho was the same.The peak time of TCA,PPP,EMP-TCA,Cyt and ALT respiratory pathway activity in Cabernet Sauvignon buds was also significantly earlier than that of roots,and the difference was 12 days,while the peak time of the bud and the root system of Early Kyoho was the same.The results showed that the time of dormancy release of Cabernet Sauvignon winter bud and root system was not synchronous,the root activity lagged behind,the change of respiratory pathway and the accumulation of respiratory substrate were slow,which led to the failure of timely supplement of water lost in branches,and then the water needed for physiological activities in shoots above ground was insufficient,which may be the main reason for the Cabernet Sauvignon happened shoots shriveling.(4)The perennial field seedlings Early Kyoho and Cabernet Sauvignon were collected to explore the correlation regression between the dynamic changes of total respiratory intensity and the effective accumulation of air and soil temperature in the same period.The results showed that the initiation of bud respiration of Cabernet Sauvignon was mainly regulated by the effective accumulated air temperature(r =0.819,r =0.724),while the initiation of root respiration was mainly regulated by the effective accumulated soil temperature(r =0.671,r=0.788).In the dormancy period of Cabernet Sauvignon root,the soil effective accumulation temperature demand and the air effective accumulation temperature demand were 2.16 times and 1.56 times respectively.In contrast,the roots and buds of the Early Kyoho peak were mainly regulated by the effective accumulation temperature of air,and the requirements of the roots and buds on the effective accumulation temperature of air and soil were the same.The difference of soil effective accumulated temperature required for dormancy release of root and bud was 127150 m and 54756 m.Therefore,it is concluded that the higher accumulated temperature required for the root system activity of Cabernet Sauvignon is the main factor that causes the above ground and underground physiological activities not to be synchronized.(5)In order to improve the ground temperature and start the water supply earlier,the perennial field seedling Early Kyoho and Cabernet Sauvignon were covered with tent.The results showed that compared with uncovered,the temperature in root area covered with tent could significantly improve to the average daily ground temperature,which is 2.67℃ higher than that of uncovered.Furthermore,the effective accumulation speed of soil temperature was 51.7% higher than uncovered.The content of soluble sugar and respiration related substrates in tented Cabernet Sauvignon roots were significantly accelerated,and the time when the activity of each respiratory pathway reached the peak value was promoted.The dormancy release time of Cabernet Sauvignon roots was 14 days earlier than that of no mulching,and the dormancy release time of winter buds was 5 days earlier than that of no mulching.The difference of dormancy release time between winter buds and roots was shortened from 12 days to 3 days.However,there was no significant effect on the time when the respiratory pathway and the content of respiratory substrate reached the peak in the Early Kyoho after mulching tent.Compared with the control group without mulching,the dormancy release time of roots and buds was only one day earlier.It can be concluded that low soil temperature and low root activity are the main reasons that make it difficult for Cabernet Sauvignon branches to obtain water in time.(6)In order to further explore the regulation of root zone temperature,two-year potted seedlings of Cabernet Sauvignon were used as experimental materials,and the dormancy release period was treated with temperature rise(t = 14 ℃)and low temperature(t = 0 ℃).The results showed that the number of new roots increased significantly with the increase of temperature,the total number of root tips increased by 36.9%,the total length and the total area of roots increased by 16.3% and 20.8% respectively.The tissue water content of the root system and branches of Cabernet Sauvignon Rose to a higher level in the period of dormancy release,about 55% and 53% respectively;At the same time,the water content of roots and branches was about 40% and 45%.The results showed that root warming treatment could significantly increase the number of absorbing roots,promote the absorption of water and reduce the occurrence of shoots shriveling. |
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