Farhan Ahmed wrote:I am a philosopher rather than a scientist...I love to see abstract rather than fact. hahaha.
Genes do play role. Their presence and absence and then further amalgamation of them.
abstract transform to facts,but not illusion and fantasy. Genes do play role. Their presence and absence and then further amalgamation of them
thats seems to be close to reality.
IMHO both factors are involved in images shared by Birg sb.
The factors that affect plant growth can be classified as genetic or environmental.
A. Genetic Factor
1. Field crops - Yield potential is determined by genes of the plant. A large part of the increase in yield over the years has been due to hybrids and improved varieties. Other characteristics such as quality, disease resistance, drought hardiness are determined by the genetic makeup. Corn hybrids are an example of a dramatic yiel incease resulting from genetics. Genetic engineering is now becoming an important tool in changing a plants potential.
B. Environmental Factors
definition - All external conditions and influences affecting the life and development of an organism.
The following are regarded as the most important environmental factors
· Temperature
· Moisture supply
· Radiant energy
· Composition of the atmosphere
· Soil aeration and soil structure
· Soil reaction
· Biotic factors
· Supply of mineral nutrients
· Absence of growth-restricting substances
Each can be a limiting factor in plant growth. These environmental factors do not act independently example - inverse relationship between soil moisture and air
a. Temperature - A measure of the intensity of heat. Plant growth occurs in a fairly narrow range - 60 - 100 degrees F
1. Temperature directly affects
photosynthesis
respiration
transpiration - loss of water
absorption of water and nutrients
2. The rate of these processes increases with an increase in temperature responses are different with different crops
3. Temperature also affects soil organisms nitrifying bacteria inhibited by low temperature. pH may decrease in summer due to activities of microorganisms
4. Soil temperature affects water and nutrient uptake
b. Moisture supply - Plant growth restricted by low and high levels of soil moisture
1. can be regulated with drainage and irrigation
2. good soil moisture improves nutrient uptake
If moisture is a limiting factor fertilizer is not used efficiently.
c. Radiant energy
Quality, intensity and duration of light are important
1. Quality can't be controlled on a field scale - Feasible on specialty crops
2. Intensity of light (brightness) is an important factor.
photosynthesis light intensity
Corn with upright leaves being bred to intercept more light
3. Duration - Photoperiodism - Plant behavior in relation to day length
- long day plants - flower only if days are longer than same critical period - 12 hours Grains and clovers
- short day plants - flower only if days are shorter than a critical period soybeans.
- indeterminate - flower over a wide range of day lengths. Tomato, cotton, buckwheat
Some crops fail to flower in certain geographical areas
Chrysanthemums can be made to bloom by controlling photoperiod.
d. Composition of the atmosphere
CO2 makes up 0.03 per cent of air by volume. Photosynthesis converts CO2 to organic material in the plant. CO2 is returned to atmosphere by respiration and decomposition
In a corn field or closed greenhouse CO2 level may drop and become a limiting factor in growth.
Increasing CO2 can increase crop yields respiration of plants and animals - decomposition of manure or plant residue may release CO2
greenhouse crops
Plant growth and quality can be enhanced by supplemental CO2. Growth responses have been shown with tomatoes, lettuce, cucumbers, flower crops, greens, peas, beans, potatoes
Air Quality
Air pollutants in sufficient quantities are toxic to plants sulfur dioxide - provides sulfur at low levels
carbon monoxide
hydrofluoric acid
e. Soil aeration
Compact soils of high bulk density and poor structure are aerated poorly.
Pore space is occupied by air and water so the amount of air and water are inversely proportional to the amount of oxygen in the soil. On well drained soils, oxygen content is not likely to be limiting to plant growth.
Plants vary widely in their sensitivity to soil oxygen. Paddy rice vs tobacco
f. Soil reaction
- pH influences availability of certain nutrients ex phosphate availability low on acid soils. Al is toxic to plants
diseases affected by pH
Potato scab controlled by keeping pH below 5.5
g. Biotic factors
disease - heavier fertilization may increase vegetative growth and susceptibility to disease
Root knot nematodes reduce absorption so more fertilizer is necessary.
insects
weeds - compete for moisture nutrients light
allelopathy - harmful substances released by roots.
h. Plant Nutrients
Essential Plant Nutrients - Those elements that are needed for higher plants to complete all life functions, and that the deficiency
can be corrected only by the application of the specific element causing the deficiency.
I will only put it to genes, if i am cent percent sure that these three were given exactly same conditions. 100 % same media, 100% same water/nutrient/exposure etc.
Farhan Ahmed wrote:I will only put it to genes, if i am cent percent sure that these three were given exactly same conditions. 100 % same media, 100% same water/nutrient/exposure etc.
My vote is with you. Lets see whats the Brig sb's view?
