Distinguish Effect of Cu, Zn and Cd on Wheat’s Growth Using Nondestructive and Rapid Minolta SPAD-502

This paper focused on the SPAD values response to different treatment levels of heavy metal Cu, Zn and Cd stress on growth of wheat. Random blocks design experiment has been carried out to simulate five concentration levels’ heavy metal Cu, Zn and Cd respectively. The in-situ SPAD values were measured for each treatment on December 8^th 2014 (seedling stage), December 13^th 2014 (tillering stage), January 8^th 2015 (tillering stage), April 18^th 2015 (elongation stage), April 30^th 2015 (booting stage), May 12^th 2015 (heading stage) and June 3^rd 2015 (filling stage) respectively using Minolta SPAD-502. The standard deviation of SPAD in different between check plot (CK) and level i, Normalized SPAD values and their variation coefficients among five heavy metal treatments for Cd, Zn and Cu have been analyzed at different measurement time. SPAD values of CK treatment decreased slightly from seedling stage to tillering stage, followed by rapid increase to elongation stage, keeping a shoulder to heading stage, then rapid decrease to filling stage. With the increase of heavy metal treatment levels, standard deviations of SPAD values between CK and level i increased gradually, and the minimum of standard deviation appeared at booting and heading stage. The Normalized SPAD had been calculated by the SPAD ratio of heavy level i to CK. The higher Normalized SPAD, the lower Normalized SPAD value with the minimum at booting and heading stage. Variance coefficients of Normalized SPAD of Cd treatments at seedling stage and tillering stages lower than Zn and Cu treatments. Normalized SPAD among Cd, Cu and Zn treatments had lowest and similar variance at booting stage and heading stages.