30-40

• Optimum temperature


  Temperature where the velocity of the reaction is at maximum
• Maximum temperature


  Temperature above which the velocity of the reaction becomes zero, due to the desaturation of enzymes
• Factors that affect temperature of the environment

  • Solar radiation
  • Surrounding land masses or bodies of water
  • Altitude
• For every 100 meter rise in elevation, there is a 0.6 °C decrease in temperature
• In the Philippines, high elevation is 13.2 - 24.6 C, low elevation is 23.3-31.5 C
• Classification of crops according to temperature requirement

  • Cool season crops (e.g. cabbage, broccoli, cauliflower)
  • Warm season crops (e.g. rice, banana)
  • Tropical (e.g. coconut)
  • Sub-tropical (e.g. citrus)
• Vernalization


  Requirement of certain crops for flowering (e.g. celery seed exposed to 4.4 - 10 C for 10 days under imbibed condition)
• Effect of temperature on crop maturation

  Crops mature faster in hotter environments than in colder ones
• Normal wind speed in the Philippines is 7.2 km/hr
• At 30 km/hr leaf tearing may already occur especially in banana and abaca
• Effects of wind on plants

  • Increase transpiration
  • Destructive effects of strong winds, typhoon (e.g. crop lodging, grain shattering)
  • Sterility due to loss of pollens
  • Disease spore dispersal
  • Reduced CO2 levels especially in enclosed spaces
  • Affects plant form
• Air circulation in the atmosphere results from the sun's radiation falling more directly on the tropical regions than on polar regions, the warmer air rises and flow forward the poles, cools and sinks as cold polar air and then returns toward the equator as ground flow
• The interactions cause the establishment of regions, large and small, each with a different climate
• Light intensity

  Expressed in foot-candle or lux
• Plants are generally spaced so that maximum leaf area is exposed to sunlight
• Shade-loving plants

  Have low light saturation point
• Some plants require subdued light to survive (e.g. some ornamentals)
• Day length

  Expressed in hours per day
• Wavelength

  Expressed in Angstrom or nanometers or identified by color
• Aspects of light important to plants

  • Light intensity
  • Duration or day length
  • Wavelength
• Effects of light on plants

  • Photoenergetic effect - direct effect on photosynthesis
  • Photocybernetic effect - effect on plant development
  • Photoperiodic effect - plant response as conditioned by daylength
• Classification of plants according to light intensity requirements

  • Heliophytes - sun loving, light saturated at about 5000 foot candles (e.g. banana, chrysanthemum, corn, cowpea, cucurbits, eggplant, papaya, peanut, sugarcane)
  • Sciophytes - shade loving, light saturated at about 500 foot candles (e.g. ginger, African violet, ferns, philodendron, coffee)
  • Intermediate group - may be converted through acclimatization into either heliophytes or sciophytes
• Classification of plants according to photoperiodic response

  • Day neutral - will flower over a wide range of daylength (e.g. banana, citrus, coconut, corn, tomato)
  • Short day plant - requires a dark period exceeding some critical length to induce flowering (e.g. coffee, kenaf, lima bean, rice, sesame, soybean, winged bean)
  • Long day plant - inhibited from flowering when the dark period exceeds some critical length (e.g. aster, castor oil, onion, radish)
• Relative humidity


  Proportion/amount of moisture in the air
• Low relative humidity and high temperature

  Result in high evapotranspiration
• High relative humidity and high temperature

  Result in low evapotranspiration
• Carbon dioxide


  Critical in enclosed environments like greenhouses
• Air pollution


  • Toxic substances like lead, sulfur dioxide, carbon monoxide, HF
• Cloudiness, including smog and fog, affect the amount of radiation received by plants. Most solar radiation is reflected by clouds.
• Climatic Stresses


  • Typhoon and weather variations
  • Ozone Destruction
  • Global warming
  • El Niño/ La niña
  • Acid Rain
  • Lahar
• Typhoon

  Strong winds with speed greater than 21 kph
• Ozone


  Protective shield against the harmful UV rays, 6-30 miles above the earth
• Harmful effects of ozone destruction

  • Depressed photosynthesis
  • Reduced seed protein, lipids and carbohydrates
• Global warming

  Increased concentration of carbon dioxide and methane gas in the atmosphere
• Climatic indicators of El Niño in the Philippines

  • Delayed onset of the rainy season
  • Early termination of the rainy season
  • Weak monsoon activity
  • Weak tropical cyclones activity
• Effects of El Niño

  • Fish kill especially cold water fish-tuna and milkfish catch declines
  • Decrease in yield for most crops
  • Human death
• Soil is a mixture of organic and inorganic materials which developed on the earth's surface through weathering process of rocks and minerals and whose properties are conditioned in various degrees by the influence of climate, living organisms, and topography acting on the parent material over a period of time
• Soil serves as a medium of plant growth (physical support for anchorage of plant roots; water and nutrient supplier)
• Soil is considered a non-renewable resource because it takes about a hundred years for natural processes to form an inch of soil
• Soil


  A natural body with dimensions of thickness and width with indistinct horizontal boundaries enabling it to blend with other soils and vertical boundaries of the air above it and the unweathered rocks below it