Research And Application Of Water Deficit Assessment Method For Plant Based On Stem Water Content

Water deficit stress is an important factor that restricts plant growth,which can induce adverse reactions such as osmotic imbalance,membrane system damage,and metabolic rate reduction,thus leading to a decline in crop yield or even death.Plant water physiology information can accurately characterize the degree of plant water deficit stress.A better way to obtain information about the water physiology of plants is conducive to the sustainable development of agriculture and forestry.At present,the traditional plant water physiological indicators(leaf water potential,transpiration rate,stem flow,etc.)are indirect indicators of plant water content,However,it is difficult to realize real-time online NDT,the testing equipment is expensive and the operation is complicated.In response to these problems,this article first developed a self-adaptive stem moisture sensor based on the dielectric properties of plants,and constructed the water deficit stress evaluation index and the deficit of the vigor tree by taking the stem moisture of the vigor tree as the research object.Finally,based on these two types of indicators,we explored the water deficit stress irrigation model of vigorous trees and analyzed the application of irrigation.The main research contents,methods and conclusions of this paper are as follows:(1)Based on the three-phase hybrid dielectric model of plant stem tissues,this article improves the stem moisture sensor independently developed by the team.We developed an adaptive stem moisture sensor,its measuring probe structure has been changed,and innovatively integrated pressure and compactness automatic control device.It not only ensures that the detection ring always has the same contact area and compactness with the stems of woody plants,but also avoids strangulation damage caused by the excessive growth of living standing trees,thereby improving the accuracy of long-term monitoring in the field.By increasing the power of the signal source(25MW),the detection radius is further expanded,so that the sensor still has good universality for plants with long age,thick epidermis and large diameter.The radial sensitive distance of the sensor is about 40 mm,the measuring range of stem volume water content is 0%-100%,and the temperature sensitivity coefficient is 2.5m V/?.(2)Based on the self-developed self-adaptive vigorous wood stem moisture composite sensor,the possibility of inverting the vital signs of living standing wood through the change law of the stem moisture of the living trees was explored,and four derivative indicators for the detection of water deficit stress of vigorous wood were constructed,through the analysis of the daily and monthly changes of the stem water of vigorous wood stems in the four different life cycles of germination,growth,deciduous and dormancy under no water stress.(3)Based on the analysis of the correlation between the stem moisture of the vigorous wood and the environmental parameters,a water deficit assessment model based on the environmental parameters and the stem water of vigorous wood was constructed,and the water deficit stress parameter ? was used to evaluate the drought stress degree of the vigorous wood.?=6.0394° is used as the index of stop of poplar irrigation,which provides quantitative data support for the water deficit stress irrigation of plants.(4)With poplar as the test object,4 water deficit stress detection indicators were determined as input variables,and water deficit stress evaluation index ? was used as output variable,and the poplar water deficit stress irrigation model was explored,and irrigation was completed based on this model.The software and hardware design of the control system has been tested and verified in two experimental nurseries.Compared with the traditional irrigation based on artificial experience,the irrigation control system based on the poplar water deficit stress irrigation model can save more than22% of water.Based on the self-developed stem water composite sensor,this paper innovatively constructs the plant water deficit stress evaluation index,water deficit stress detection index and water deficit stress irrigation model,which provides a new theoretical basis for the formulation of precise water-saving irrigation strategies for plants.