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Chang Li

Bio: Chang Li is an academic researcher. The author has contributed to research in topics: RGB color model. The author has an hindex of 1, co-authored 1 publications receiving 3 citations.

Papers
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Journal Article
TL;DR: The results indicate that the present model has a good performance in predicting leaf color changes at different leaf positions in rice under different growth conditions, and thus lays a foundation for further constructing digital and visual rice growth system.

5 citations


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Journal ArticleDOI
Hu Yang1, Jinwen Li, Jingping Yang1, Hua Wang1, Junliang Zou1, Junjun He1 
10 Feb 2014-PLOS ONE
TL;DR: A quadratic equation was utilized to describe the relationship between SPAD readings and leaf age during the leaf senescence period, and the rate of decrease inSPAD readings increased with the age of leaves, but the rate was slowed by N application.
Abstract: A Soil-Plant Analysis Development (SPAD) chlorophyll meter can be used as a simple tool for evaluating N concentration of the leaf and investigating the combined effects of nitrogen rate and leaf age on N distribution. We conducted experiments in a paddy field over two consecutive years (2008–2009) using rice plants treated with six different N application levels. N distribution pattern was determined by SPAD readings based on the temporal dynamics of N concentrations in individual leaves. At 62 days after transplantation (DAT) in 2008 and DAT 60 in 2009, leaf SPAD readings increased from the upper to lower in the rice canopy that received N levels of 150 to 375 kg ha−1The differences in SPAD readings between the upper and lower leaf were larger under higher N application rates. However, as plants grew, this atypical distribution of SPAD readings in canopy leaf quickly reversed to the general order. In addition, temporal dynamics of the leaf SPAD readings (N concentrations) were fitted to a piecewise function. In our model, changes in leaf SPAD readings were divided into three stages: growth, functioning, and senescence periods. The leaf growth period lasted approximately 6 days, and cumulative growing days were not affected by N application rates. The leaf functioning period was represented with a relatively stable SPAD reading related to N application rate, and cumulative growing days were extended with increasing N application rates. A quadratic equation was utilized to describe the relationship between SPAD readings and leaf age during the leaf senescence period. The rate of decrease in SPAD readings increased with the age of leaves, but the rate was slowed by N application. As leaves in the lower canopy were physiologically older than leaves in the upper canopy, the rate of decrease in SPAD readings was faster in the lower leaves.

50 citations

Journal ArticleDOI
TL;DR: In this article, the color changes of main stem leaves of two kinds of rice variety under different growth periods and nitrogen levels were analyzed to improve the authenticity and practicability of visualization color model of virtual rice.
Abstract: This paper presents a research object with the color changes of main stem leaves of two kinds of rice variety under different growth periods and nitrogen levels to improve the authenticity and practicability of visualization color model of virtual rice. The authors at first build an RGB-SPAD mathematic model of rice leaf; then obtain the leaf rendering equations via the BRDF diffuse reflection formulas; and at last apply the C++ language combined with the OpenGL graphics library programming to render and visualize appearances of the rice leaves. The leaf visualization color model constructed by this method accords with the law of rice growth, and thus it is expected to provide assistance in decision making to regulate and control the fertilizer level for rice cultivators according to the changes of leaf color.

7 citations

Proceedings Article
10 Dec 2010
TL;DR: In this article, a framework for the color simulation of mini-cucumber leaves is presented, where the shape and main venation information of the leaves are extracted and a quadratic function is used as base color function to simulate the color transition during the fruit seting period and fruit maturation period.
Abstract: This paper presents a framework for the color simulation of mini-cucumber leaves At first, extract the shape and main venation information of the mini-cucumber leaves Secondly, construct a quadratic function as base color function to simulate the color transition during the fruit-seting period and fruit maturation period Finally we use the cellular texture basis function and adjustment function to describe the color distribution in structure space Experimental results show that the proposed method could simulate the color of minicucumber leaves This provides a simple and general process simulation for the leaf color of plants
TL;DR: In this paper , the authors used a soilplant analysis development (SPAD) meter for non-destructive monitoring of leaf chlorophyll dynamics to characterize the patterns of spatio-temporal variation in the nutritional status of maize leaves under three nitrogen treatments in two cultivars.
Abstract: The spatio-temporal variation of leaf chlorophyll content is an important crop phenotypic trait that is of great significance for evaluating crop productivity. This study used a soilplant analysis development (SPAD) chlorophyll meter for non-destructive monitoring of leaf chlorophyll dynamics to characterize the patterns of spatio-temporal variation in the nutritional status of maize (Zea mays L.) leaves under three nitrogen treatments in two cultivars. The results showed that nitrogen levels could affect the maximum leaf SPAD reading (SPADmax) and the duration of high SPAD reading. A rational model was used to measure the changes in SPAD readings over time in single leaves. This model was suitable for predicting the dynamics of the nutrient status for each leaf position under different nitrogen treatments, and model parameter values were position dependent. SPADmax at each leaf decreased with the reduction of nitrogen supply. Leaves at different positions in both cultivars responded differently to higher nitrogen rates. Lower leaves (8th–10th positions) were more sensitive than the other leaves in response to nitrogen. Monitoring the SPAD reading dynamic of lower leaves could accurately characterize and assess the nitrogen supply in plants. The lower leaves in nitrogen-deficient plants had a shorter duration of high SPAD readings compared to nitrogen-sufficient plants; this physiological mechanism should be studied further. In summary, the spatio-temporal variation of plant nitrogen status in maize was analysed to determine critical leaf positions for potentially assisting in the identification of appropriate agronomic management practices, such as the adjustment of nitrogen rates in late fertilization.
DOI
TL;DR: In this paper , the authors used a soil-plant analysis development (SPAD) meter for non-destructive monitoring of leaf chlorophyll dynamics to characterize the patterns of spatio-temporal variation in the nutritional status of maize leaves under three nitrogen treatments in two cultivars.
Abstract: Abstract The spatio-temporal variation of leaf chlorophyll content is an important crop phenotypic trait that is of great significance for evaluating crop productivity. This study used a soil-plant analysis development (SPAD) chlorophyll meter for non-destructive monitoring of leaf chlorophyll dynamics to characterize the patterns of spatio-temporal variation in the nutritional status of maize (Zea mays L.) leaves under three nitrogen treatments in two cultivars. The results showed that nitrogen levels could affect the maximum leaf SPAD reading (SPADmax) and the duration of high SPAD reading. A rational model was used to measure the changes in SPAD readings over time in single leaves. This model was suitable for predicting the dynamics of the nutrient status for each leaf position under different nitrogen treatments, and model parameter values were position dependent. SPADmax at each leaf decreased with the reduction of nitrogen supply. Leaves at different positions in both cultivars responded differently to higher nitrogen rates. Lower leaves (8th–10th positions) were more sensitive than the other leaves in response to nitrogen. Monitoring the SPAD reading dynamic of lower leaves could accurately characterize and assess the nitrogen supply in plants. The lower leaves in nitrogen-deficient plants had a shorter duration of high SPAD readings compared to nitrogen-sufficient plants; this physiological mechanism should be studied further. In summary, the spatio-temporal variation of plant nitrogen status in maize was analysed to determine critical leaf positions for potentially assisting in the identification of appropriate agronomic management practices, such as the adjustment of nitrogen rates in late fertilization.