Study On Key Technologies For Measuring Physiological Index And Growth Rate Of Masson Pine Seedlings

Masson pine is the main afforestation tree species in southern China.The quality of seedlings plays a key role in the success of afforestation.Morphological index,physiological index and dynamic index are three main aspects of evaluating seedling quality.Traditional measurement methods are not only complicated and time-consuming,but also inefficient in accuracy and damage to seedlings themselves.Therefore,it is particularly important to study efficient,economical and non-destructive measurement methods.The purpose of this paper is to study the key techniques for determining the physiological indexes and growth rate of masson pine seedlings.Near infrared spectroscopy(NIRS)and laser speckle technique were used to detect the physiological index and root growth rate of masson pine seedlings rapidly and accurately,separately.This paper is mainly divided into the following two parts:(1)In this paper,near infrared spectroscopy was used to detect water content in root of masson pine seedlings rapidly,accurately and nondestructively.Near Infrared Spectroscopy is widely used in material content prediction due to its nondestructive and fast characteristics.In this paper,a spectral analysis model of variable weighted stacked autoencoders combined with support vector machine regression is proposed to predict water content in masson pine seedlings roots.Variable weighted stacked autoencoders are used to extract output-related features layer by layer,and support vector machine regression is used to further accurately predict water content according to the features generated by autoencoders.The experimental results show that,compared with the results of other commonly used models,the proposed model achieves the best performance in root water prediction of masson pine seedlings.Specifically,the R~2 is 0.9708 and RMSE is 0.6358 in the calibration set,while the R~2 is 0.94 and RMSE is 1.03 in the prediction set.(2)In this paper,the laser speckle technique is applied to the detection of micro-displacement changes in seedling roots.The probability density function of laser speckle phase is analyzed by statistical interferometry in optical interferometry to get the object phase,and then the morphological changes of seedling roots are measured in a short time.Thus the traditional judgment of root morphological changes is shortened from a month to a few seconds,and the measurement accuracy is improved.At the same time,the comparison with the traditional macro-scale measurement method is made,which shows the adequacy of statistical interferometry in monitoring the growth dynamics of plant roots at nanoscale.The experimental system studied in this paper replaces the traditional method of measuring physiological index and growth rate of seedlings,and achieves more accurate,stable and reliable results.And it is feasible to be used as an advanced technical means to evaluate the quality of seedlings.