• Abscisic acid is used as a cotton defoliant.
• Cycocel is used for reducing excessive vegetative growth in cotton.
• Cycocel is used as dwarfing agent in wheat.
• NAA increases number of flowers.
• Gibberellins are used for production of seedless grapes.
• Gibberellins are used for increasing size of fruits.
• S-shaped or sigmoid curve is typical of growth pattern of individual organs, of a whole plant and of population of plants.
• In lag period internal changes occur that are preparatory to growth. Increase in size or weight is negligible.
• In log phase or grand period of growth, growth is very fast. Logarithm of growth when plotted against time is a straight line.
• Justus Von Liebig proposed law of minimum in 1862.
• Blackman in 1905 propose law of optima and limiting factors.
• Mitcherlich’s law of diminishing returns was proposed by Mitcherlich in 1909.
• Wilcox proposed inverse yield-nitrogen law in 1929.
• According to inverse yield nitrogen law, yielding ability of any crop plant is inversely proportional to the mean nitrogen content in dry matter.
• Macy-poverty adjustment law was proposed by Macy in 1936.
• Watson developed the concept of leaf area Index (LAI).
• Leaf area index = Leaf area Ground area
• Yield of dry matter is a function of leaf area, net assimilation rate and duration of leaf area.
• The total drymatter produced by a crop is known as biological yield.
• Fraction of the biological yield which is useful for man is known as economic yield.
• Biological yield × K = Economic yield. K is a constant and called harvest index or coefficient of effectiveness.
• Harvest index = Economic yield/Biological yield
• In many cereals, most of the drymatter in the grain is produced by photosynthesis after the ears emerge.
• Most of the dry matter of the grain is produced by the part of the shoot above the flag leaf node.
• Flag leaf contributes nearly 40% of the total dry matter in many cereals.
• In cereals, grain filling is largely dependent on photosynthesis and environmental conditions after flowering.
• In cereal, capacity for storage is determined by conditions before flowering.
• In plants where source and sink are developed simultaneously, like groundnut, redgram, cotton etc., the adjustment of two components may be more readily achieved.
• Economic yield is expressed as function of yield attributes
Y = a × b × c × d
a = final plant population at harvest
b = number of effective tillers (panicle or ear producing)
c = number of filled grains/ear
d = weight of individual grain
• Instead of individual grain weight, 100-grain weight (in case of bold grains) and 1000 grain weight (in case of small sized grains) are taken as yield attribute and this is also known as test weight.
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