Real-time Observation On Cavitation In Xylem And Study On The Change Of Physiological Index Of The Sycamore Cutting Branch

Cavitation occurred in the conduits of xylem when the plants under water stress, then it caused embolism which reduced hydraulic conductivity of plants, even more made them dead on the condition of severe draught stress. This paper took sycamore cutting branches as research object and to study the relationship between the physiological index and permanent wilting by controlling water. The experimental results showed that the water potential of branches had the minimum value at14:00and became lower with the more severe dryness. The photosynthetic rate and transpiration rate showed a variation of a single peak, most of them came to the maximum value at10:00and then dropped. The transpiration rate and stomatal conductance could not be detected and parts of plants were dead four days after the dryness. Even though, we still find that embolism could be shortly repaired in the branches under slight dryness. We thought that the loss of water is the major factor lead to the death of plants since the water potential and the photosynthetic rate reduced on the condition of what.Shen proposed three types of the cavitaion process in the conduits, but which had not been confirmed. This research took real-time observation on the cavitation process in the conduits of rice and maize leaf by use of X-ray to find out the possible mechanism of cavitation. We captured the process of the air bubble blew up immediately, which correspond the fist type. Also we found that the first type was the most common type in the daily cavitaion.