Study On Measurement System Of Stomatal Traits In Living Maize Leaves

As a channel for gas exchange between leaves and the environment,stomata play an important role in the regulation of carbon and water cycles during plant growth.With the development of microscopy and biotechnology,stomatal research has become a key topic in crop breeding and stress analysis.Measuring stomatal traits is the first step in stomatal research.The existing methods for measuring stomatal traits are destructive and inefficient which makes high-throughput analysis difficult in the whole growth stage of plants.To resolve the above problems,two portable microscopes are used to acquire stomatal images of living maize leaves and a measuring system is developed to extract stomatal traits automatically.To evaluate the performance of the system,water stress experiments are carried out.The main contents and results are as follows.(1)Study on the extraction method of stomatal traits.Two portable microscopes with different resolutions are used to acquire images of stomata in living maize leaves.For the images acquired by Tip Scope,stomata detection model is established based on Feature Pyramid Networks(FPN)and stomatal density is calculated.The accuracy,recall,precision,and F1 score of the stomata detection model are 0.99,0.99,99%,and 0.99,respectively.The square of the correlation coefficient(R2)of the manual measurement values versus the automatic measurement values for stomatal density is 0.99 and the mean absolute percentage error(MAPE)is 1.03%.For the images acquired by Pro Scope HR2,the stomatal number model and stomatal coordinate model are established based on Faster RCNN to identify opening or closing stomata.For the opening stomata,an improved CV model is used to segment pores of them and a total of 6 pore traits are measured.The results show that the accuracy,recall,precision,and F1 score of the two models for opening stomata detection are 0.99,0.96,95%,0.97,and 0.99,0.96,96%,0.98,respectively.The accuracy,recall,precision,and F1 score of the two models for closing stomata detection are 0.96,0.95,92%,0.95 and 0.97,0.95,93%,0.96,respectively.Compared with the manual measurements,the R2 of the opening and closing stomata are higher than 0.98,and the MAPE are lower than 7%.The R2 of the pore traits are higher than 0.85,and the MAPE are lower than 7%.(2)Development of small greenhouse.In order to study the influence of environment on stomatal traits,a small greenhouse is developed.Two temperature and humidity sensors are used to collect the temperature and humidity,and the STM32F103VET6 microcontroller is used to control the temperature and humidity.A software interface is developed in the QT platform to monitor the temperature and humidity in the small greenhouse.The temperature control range of the small greenhouse is 24 ℃～45 ℃(25 ℃,70% RH)and the humidity control range is 15% RH～90% RH(25 ℃,70% RH).The light intensity is set to be 1800 lux.The temperature control accuracy is ±1 ℃,and the humidity control accuracy is ±5% RH.(3)Experiments and Analysis.Water stress experiments are carried out for two types of maize,wild-type B73 and mutant Zmfab1 a.The stomatal density of them are obtained based on the Tip Scope portable microscope.The results show that the stomatal density of maize at the jointing stage will gradually increase during the growth and development process,and the stomatal density of the mutant Zmfab1 a is lower than that of the wild type B73.The number of opening and closing stomata and 6 pore traits are obtained based on the Pro Scope HR2 portable microscope.The results show that under normal watering conditions,the ratio of opening stomata number to total stomata number and total pore area of B73 are higher than those of Zmfab1 a,but are negative under drought treatment conditions.After drought stress and re-watering treatment,Zmfab1 a has a higher ability to recover leaf stomata after stress than B73.Based on the developed small greenhouse,the effect of ambient temperature on stomatal traits is studied.The results show that maize stomata open less below 30 ℃,and more open between 30 ℃ and 40 ℃.However,when the temperature continues to rise to 45 ℃,the stomatal opening ratio and opening degree decrease sharply.In addition,the dynamic changes of stomata in maize and wheat are observed by Pro Scope HR2 portable microscope and the improved CV model method is suitable for stomatal pore segmentation of other nine crops.