R2103 5.1 Explain why plant disorders need to be controlled

Question 1

What is a plant disorder

Answer 1

A condition in the plant resulting from a non-living (abiotic) factor such as an environmental factor, a nutrient or water being present at the incorrect level, or genetic disorder

Question 2

How are plants affected by frost

Answer 2

1. Causes plant cells to freeze damaging the cell wall
2. Growth becomes limp, damaged and distorted
3. Evergreen plants turn turn brown and leaves of tender plants take on a translucent appearence
4. Made worse in morning sun as defrosting quickly damages the cell walls

Question 3

How are plants affected by shade

Answer 3

1. Growth will become leggy
2. Golden of variegated foliage generally reverts to greener form
3. Some plants will thrive in low-light conditions
4. Plants growing in shade must compete with trees, shrubs for nutrients, water, and tolerate poor air circulation

Question 4

Types of shade (4)

Answer 4

1. Light shade - an area that is shaded, but bright
2. Partial or medium shade - direct sun rays are blocked for most of the day
3. Full shade - Little to no direct sunlight reaches the ground. May be reflected light from sunnier areas
4. Dense shade - full shade under thick canopies of trees. Areas under stairwells, decks or covered patios on the north side of a house receive full shade.

Question 5

How are plants affected by drought

Can have both long term and short term droughts

Answer 5

1. Pattern of damage or death occurs from top of plant down and from outside plant inward
2. Plant wilt - one of the first sign as loss of turgidity
3. Woody plants show decrease in growth or have no growth
4. Plants may leaf out, then die later in the growing season because of depleted food reserves. May occur a few year after major drought
5. Winter kill. Reduction in hardiness as result of reduced food production
6. Gummy exudates appear on twigs, branches, trunks
7. Suckers develop on branches and trunk
8. Heavy seed production may occur
9. Wood or bark cracks

Question 6

How are plants affected by water-logging

Answer 6

1. Water fill air spaces between soil particles and prevents oxygen from reaching the roots. This causes soil to stagnate and prevents root growth
2. Yellow leaves that wither and drop.
3. Plants may look like they need water
4. Wilting may occur
5. Surface if soil is wet with puddles in it
6. When lifted plant roots are black soft and soggy and soil smells of rotten eggs
7. Plant growth stunted and can be die back
8. Compaction can make drainage worse
9. Waterlogging, and compaction, create environment for diseases such as phytopthora

Question 7

How are plants affected by fasciation

Stems grow abnormally because of a disturbance in stem apex

Answer 7

Can be caused by:
1. Random genetic mutation
2. Bacterium Rhodococcus fascians
3. Viral infection
4. Damage to plants by frost, animals, chemical or mechanical injury
5. Flattened shoots, or shoots that appear to be composed of several fused shoots, and flattened elongated or misshapen flowerheads
6. Some fasciated plants are propagated to maintain their unusual forms e.g. Salix udensis

Question 8

How are plants affected by rose balling

Answer 8

1. Outer petels of a rose die and become stiff
2. Inner petals are prevented from emerging to produce a normal bloom
3. Often cause by damp, cool, shady conditions
4. Wet outer petals are not able to dry out before being sorched by the sun
5. Buds may also be covered in a grey mould
6. Most acute on roses with thin petals

Question 9

How are plants affected by lime induced chlorosis

Answer 9

1. Leaves turn yellow - starting at margins and spreading up between viens.
2. Young growth affected first
3. Brown patches may occur at leaf margins
4. As leaves turn yellow less food is produced
5. High alkalinity of the soil can make iron and magnesium unavailable to plants, causing leaf chlorosis

Question 10

How are plants affected by low temperatures

Answer 10

1. Slows plant growth, resulting from a reduced rate of photosynthesis

Question 11

How are plants affected by high temperatures

Answer 11

1. Effects differ with species
2. At upper level of tolerance photsynthesis slows down as enzymes become less efficient
3. Leaf margin can dry off
4. Sunscald - occurs on fruit suddenly exposed to high temperatures. Affected areas are straw coloured or white, soft, sunken and wrinkled.