1. 6.4 External Factors that Affect Plant Growth

2. Nutrients Macronutrients: Micronutrients:
Nutrients needed in amounts greater than 1% of dry weight
Micronutrients:
Nutrients needed in much smaller amounts
Cl, Fe, B, Mn, Zn, Cu

3. Function of Macronutrients
Nitrogen (N)
Part of chlorophyll, proteins and nucleic acids
Potassium (K)
Controls opening/closing of stomata
Calcium (Ca)
Component of cell walls and membranes
McGraa Hill page 597

4. Function of Macronutrients
Magnesium (Mg)
Part of chlorophyll, needed to make proteins
Phosphorus (P)
Part of proteins, nucleic acids and cell membranes
Sulfur (S)
Part of many proteins
McGraa Hill page 597

5. pH levels Some plants thrive in acidic soil (pH 6-7):
Pine, spruce, dogwood, blueberry, hydrangea, magnolia, holly, potatoes

6. pH levels Some plants thrive in basic soil (pH 7-8)
Geraniums, petunias, lawn grass, beans, beets, lettuce, pears, plums

7. Light Requirements Photoperiod: the number of daylight hours
Short-day plants flower and reproduce when photoperiods are shortening, example is chrysanthemum
Long-day plants flower and reproduce when the photoperiods are lengthening, example spinach

8. Light Requirements Only 1% of radiant energy is captured by plants
Chlorophyll
Red and blue spectrum
Carotenoids
Blue green and violet spectrum