plant disorders

Question 1

what is meant by plant disorder?

Answer 1

symptoms not caused by pests or disease, it is environmental, genetic or an incorrect nutrient/water level

Question 2

name some mains causes of plant disorders

Answer 2

frost
low temperature/high temperature
shade
drought
water-logging
high humidity
incorrect soil pH
nutrient deficiencies
excess fertilizer
fasciation
reversion

Question 3

what is oedema and what does it affect?

Answer 3

raised corky spots on the under surface of leaves.

seen on Rhododendron and violets.

Question 4

where is oedema most common and why?

Answer 4

in greenhouses, due to over-watering, lack of heat and poor ventilation.

winter, early spring and extended periods of cool cloudy weather favour it.

warm, moist soil and cool, moist air severely brings on the condition.

Question 5

what conditions favour oedema?

Answer 5

the roots’ ability to supply the leaves with water exceeds the leaves’ ability to release the water by transpiration.

Question 6

preventative methods are?

Answer 6

ventilation and heating in a greenhouse