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Title: ANALYSIS OF SEED GROWTH BY LINEAR INCREASE IN HARVEST INDEX

Author
item BINDI, M. - DISAT, FLORENCE, ITALY
item Sinclair, Thomas
item HARRISON, J. - UNIV OF FLORIDA

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Understanding and describing seed growth has been a major challenge in research on the formation of crop yield. USDA, Agricultural Research Service scientists at Gainesville, FL analyzed two competing concepts for describing seed growth. The more straightforward and traditional approach was to measure the growth rate of individual seeds, and multiply this growth rate by the number of seeds per unit land area. Recently, the idea has emerged that a more stable method for describing seed growth is to normalize total seed weight by the total plant weight and measure the increase in this ratio. This ratio is identified as the harvest index method. The analysis presented in this paper showed that both approaches could be described by simple linear expressions of increase as a function of time for most of the seed growth period. However, a comparison of stability in the linear expressions of the two methods across various growth conditions indicated that the harvest index approach resulted in more stable results. Hence, it was concluded that the linear increase in harvest index was a more robust and experimentally a simpler method for describing crop seed growth.

Technical Abstract: A convenient and stable method for expressing crop seed growth is important both in experimental and simulation studies. The conventional approach has been to measure the seed growth rate (SGR) of individual seeds and multiply this by the number of seeds per unit ground area. Aside from questions about obtaining a representative individual SGR and estimating seed number, there has been little resolution whether total plant SGR can be truly represented as a constant. An alternative to measurements of SGR has emerged from the observation that during seed growth, harvest index (HI) increases linearly over time. Again, there has been little intensive analysis of the question whether dHI/dt is truly constant over the entire seed growth period. Regression analyses was performed on 22 data sets representing four crop species for which there were intensive measures of seed growth and HI. These analysis showed that SGR and dHI/dt was not constant for the entire seed growth period, but constant values were a good approximation on the average for the period from 0.1 to 0.9 of maximum seed weight or harvest index. In examining the stability of SGR and dHI/dt for individual cultivars, it was found that the coefficient of variation for dHI/dt was less than SGR.