[Adaptability of cucumber plug seedlings to daytime temperature].

Cucumber plug seedlings were cultured in a phytotron to study their responses to different daytime temperature. The daytime temperature was controlled at 30 degrees C, 27 degrees C, 24 degrees C, 21 degrees C, 18 degrees C and 15 degrees C, and the night temperature was at 15 degrees C, with the thickness and length of hypocotyl, length and width of the first and the second leaves, dry matter accumulation of above- and underground parts, leaf moisture content, and leaf chlorophyll fluorescence parameters measured. Principal component analysis and clustering analysis were made to analyze the seedling quality under different temperature treatment. There existed significant differences in the test growth indices among different treatments, with the seedling quality decreased at the daytime temperature 24 degrees C > 21 degrees C > 27 degrees C > 30 degrees C > 18 degrees C > 15 degrees C. All the daytime/nighttime temperature treatments could be classified into three groups, i.e., optimum temperature (24 degrees C/15 degrees C), appropriate temperature (21 degrees C/15 degrees C), and inappropriate temperature, and the inappropriate temperature could be further subdivided into two groups, i.e., high-temperature inhibition (27 degrees C/15 degrees C, 30 degrees C/15 degrees C) and low-temperature inhibition (15 degrees C/15 degrees C, 18 degrees C/15 degrees C).

[Determination of total nitrogen content in fresh tea leaf using visible-near infrared spectroscopy].

To monitor tea tree growth and nitrogen nutrition in tea leaves, visible-near infrared spectroscopy was used to determine total nitrogen content. One hundred eleven fresh tea leaves of different nitrogen levels were sampled according to different tea type, plant age, leaf age, leaf position and soil nutrients, which covered a wide range of nitrogen content. Visible-near infrared reflectance spectra were scanned under the sunlight with a portable spectroradiometer (ASD FieldSpec 3) in field. The software of NIRSA developed by Jiangsu University was used to establish the calibration models and prediction models, which included spectra data editing, preprocessing, sample analysis, spectrogram comparison, calibration model and prediction model, analysis reporting and system configuration Eighty six samples were used to establish the calibration model with the preprocessing of first/second-order derivative plus moving average filter and the algorithm of PLS regression, stepwise regression, principal component regression, PLS regression plus artificial neural network and so on The result shows that the PLS regression calibration model with 7 principal component factors after the preprocessing of first-order derivative plus moving average filter is the best and correspondingly the root mean square error of calibration is 0. 973. Twenty five unknown samples were used to establish the prediction model and the correlation coefficient between predicted values and real values is 0.8881, while the root mean square error of prediction is 0. 130 4 with the mean relative error of 4.339%. Therefore, visible-near infrared spectroscopy has a huge potential for the determination of total nitrogen content in fresh tea leaves in a rapid and nondestructive way. Consequently, the technique can be significant to monitoring the tea tree growth and fertilization management.

[Real-time analysis of soil moisture, soil organic matter, and soil total nitrogen with NIR spectra].

The grey-brown alluvial soil in northern China was selected as research object, and the feasibility and possibility of real-time analyzing soil para-fueter with NIR spectroscopic techniques were explored. One hundred fifty samples were collected from a winter wheat farm. NIR absorbance spectra were rapidly measured under their original conditions by a Nicolet Antaris FT-NIR analyzer. Three soil parameters, namely soil moisture, SOM (soil organic matter) and TN (total nitrogen) content, were analyzed. For soil moisture content, a linear regression model was available, using 1920 nm wavelength with correlation coefficient of 0.937, so that the results obtained could be directly used to real-time evaluate soil moisture. SOM content and TN content were estimated with a muviaiple linear regression model, 1870 and 1378 nm wavelengths were selected in the SOM estimate model, and 2262 and 1888 nrameter wavelengths were selected in the TN estimate model. The results showed that soil SOM and TN contents can be evaluated by using NIR absorbance spectra of soil samples.