Methods For Observing Plant Physiological Water Adaptability Based On The Combined Measurement Of Stem Diameter And Sap Flow

With more and more severe water scarcity, water-saving irrigation technology has developed rapidly. It has a great significance to unederstand fully the process of plant water balance and observe the process of plant physiological water adaptability for selecting an ideal irrigation index and developing scientific irrigation strategies. The process of plant physiological water adaptability can be observed from the "aboveground part" and "underground part". Dynamics of the plant water can reflect the plant physiological water adaptability of "aboveground part", while the plant physiological water adaptability of "underground part" can be indicated by the root pressure. Currently, the measuring methods for stem water content and root pressure are usually harmful to plants, especially unsuitable for small plants.The stem diameter variation and sap flow are easily affected by environmental and meteorological factors, and each of them can only reflect the water information of the plant local parts. So the combined measurement of stem diameter and sap flow is more meaningful for sdudying on the plant water dynamics. Considering that the two parameters can realize nondestructive measurement, we used computational plant biology method and developed mathematical models with stem diameter and sap flow rate as inputs to measure the plant water (aboveground part) and the root pressure(underground part), in order to monitor the complete process of the plant physiological water adaptability, non-invasively. The main contents and results could be summarized as follows:1) We observed variations of the stem diameter and the sap flow rate. Stem diameter and stem flow rate both showed a diurnal variation. Every morning the daily maximum setm diameter arose, and then it decreased to the daily minimum stem diameter at noon. On the contrary, the sap flow rate changed in the opposite patter. Both stem diameter and sap flow ratecorrelated with environmental and meteorological factors. For example, vapor pressure deficit had greater influence on stem diameter variation, while the sap flow rate was largely influenced by photosynthetic active radiation.2) We developed a method for observing the physiological water adaptability of the plant stem based on a sap flow sensor. Using a commercial packaged sap flow sensor and a high precision electronic balance, complemented with our mathematical model, we non-destruclively observed the stem physiological water adaptability of the plant "aboveground part". The consistency of changing trend between the stem water content and the stem diameter further proved the reliability and the effectiveness of the method. Even though only sunflower samples and tomato samples were investigated, it could be applied for other herbaceous plants, which have similar tissue and water transport systems.3) We developed a method for monitoring non-invasively the physiological water adaptability of the plant root pressure based on Steppe water flow and storage model. By changing the algorithm order of the Steppe water flow and storage model innovatively, we not only completed the evaluation of the Steppe water flow and storage model, but also solved the problem of continuously measuring root pressure non-invasively and realized non-invasively observing the plant root pressure physiological water adaptability of the "underground part".4) On the basis of the combined measurement of stem diameter and sap flow, we observed the complete process of the physiological water adaptability for herbaceous plants non-invasively, including the daytime drainage process of the plant water and the nighttime replenishment process of the root pressure.