Disorders Flashcards
State the definition of a plant disorder.
An unhealthy condition in a plant caused by a non-living (abiotic) factor, such as an environmental factor (low/high temp, shade, excess light/wind etc), incorrect soil conditions (eg nutrient availability, water, pH of growing medium), a genetic or other problem with a plants growing habit (eg reversion, fasciation).
Describe how plants are affected by Frost, along with two methods of preventing and/or ameliorating potential damage.
DAMAGE: Frosty conditions freeze the water in plant cells, which expands and this kills the cell. Hardy plants can cope with the normal freeze/thaw cycle in the winter, but late or early frosts can do a lot of damage, even to hardy plants, as juvenile growth, flowering and fruiting in most plants is not meant to take place during cold weather. Frost is particularly damaging to flowers and fruits, and will reduce yield/attractiveness.
CONTROL: Protect less hardy and tender plants in winter by bringing them under cover, mulching with straw or plastic on the soil surface or around the pot. Right plant right place. Plant out tender specimens after all risk of frost has passed (Cultural).
Remove damaged parts of plants to prevent diseases taking hold.
Describe how plants are affected by Shade, along with two methods of preventing and/or ameliorating potential damage.
DAMAGE: Insufficient light prevents plants from photosynthesising. The plants response is to grow taller, putting its energy into height rather than leaves, called etiolated growth. Stems are long, thin and “leggy”, with fewer, smaller, paler leaves than a normal specimen.
CONTROL: Right plant right place. Plant shade tolerant plants in darker patches (eg Hydrangea macrophylla, Camellia japonica). Ensure plants have sufficient light by trimming neighbouring plants back and removing shade objects if possible (Cultural).
Move plant if its not happy to a position with more suitable conditions (Physical).
Describe how plants are affected by Drought, along with two methods of preventing and/or ameliorating potential damage.
DAMAGE: Water stress impacts quickly on young plants (limited root mass), container plants and plants in sandy soils (less water in soil), or plants in windy/exposed conditions (excess transpiration). Symptoms appear as wilting, dry, brown patches on leaves, leaf drop and death. Irregularly watered plants can develop distorted stems, leaves, flowers and fruit in response to the variable water pressure within the vascular system. Lack of water makes plants stressed and therefore more susceptible to attack by pests and diseases, eg aphids. Powdery mildews may appear on plants that are kept too dry.
CONTROL: Regular, efficient watering is key. Also, soil structure maintenance to improve water retention, by digging in OM. Right plant right place - using drought tolerant plants like Lavandula angustifolia instead of more thirsty plants like Hydrangea spp. in drier spots, or in sandy or chalky soils (Cultural).
Mulching soil during dry periods to prevent surface evaporation, making sites more sheltered by introducing wind breaks such as hedging, fencing or netting (Physical).
Describe how plants are affected by Waterlogging, along with two methods of preventing and/or ameliorating potential damage.
DAMAGE: Soils that are too moist restrict the availability of oxygen to the roots. This results in the plant being forced to respire anaerobically, which will after a short while cause problems for the plant, and eventually lead to the plants death. In addition, the roots may rot, and can also lead to fungal infections (eg Grey Mould, Damping Off). Soils that are waterlogged will also not be as biodiverse and may encourage pests such as eelworms.
CONTROL: Do not overwater. Improve drainage of waterlogged areas by improving soil structure. Right plant right place - areas that are naturally damp will need thought given to planting choices. Certain plants such as Iris pseudocorus will be happy in waterlogged conditions. (Cultural)
Areas which have problems such as excess runoff, broken drains can be sorted by installing or mending drains or soakaways. (Physical)
Describe how plants are affected by High Temperatures, along with two methods of preventing and/or ameliorating potential damage.
DAMAGE: Plants exposed to high temperatures will be prone to wilting, despite closing the stomatas and stopping respiring during hot periods to conserve water. At extremely high temperatures plant enzymes will be destroyed, impacting functions like respiration and photosynthesis and killing sections or all of the plant. Hot, dry conditions will stress the plant and make attack from pests and diseases more likely, eg Spider Mites. Most likely to happen in a protected environment that is not being properly monitored. Warm temperatures can be problematic when growing cool weather crops in summer, eg Spinach, which will bolt.
CONTROL: Monitor glasshouses and cold frames frequently during warm weather, ventilate, introduce shading and damp down when necessary. Grow cool weather crops in the correct season (Cultural).
Describe how plants are affected by Soil pH, along with two methods of preventing and/or ameliorating potential damage.
DAMAGE: Soils are ideally around 6.5 pH, which ensures the highest amounts of all necessary nutrients are available to plants. When soils are above or below this level, nutrient deficiencies can occur, impacting on plant condition, vitality and yield. This can be especially noticeable when growing plants specialised for certain pH levels outside of these conditions. Eg Lime Induced Chlorosis occurs when growing Calcifuges in alkaline conditions. Chlorosis occurs in the leaves, starting in the newest leaves first, and plant growth will be stunted, as the plant cannot access the mineral Iron from the alkaline soil.
Aside from nutrient accessibility, acidic soil has fewer soil organisms present, which can impact soil structure, plus certain pests and diseases thrive in acidic soil, such as Clubroot and eelworms.
CONTROL: Right plant, right place (Cultural).
Changing the pH of the soil by small amounts is possible. To increase the pH on soils that are too acidic, gardeners can ‘Lime’ the soil by introducing a strong alkaline substance to the soil, either inorganic such as dolmitic limestone, calcium carbonate etc, or organic, such as spent mushroom compost. To reduce the pH of alkaline soils, sulphur (inorganic) or conifer needles (organic) can be added to the soil (Physical).
Describe how plants are affected by Rose Balling, along with two methods of preventing and/or ameliorating potential damage.
DAMAGE: Caused by cool damp conditions, where the outer layers of the flower (usually double flowers like Roses, Peonies, Camellia etc) get wet and are not able to dry out before they are scorched by direct sunlight. This fuses the outer petals together, and prevents the flower bud from opening. The bud then rots in situ, and can then go on to develop Grey Mould, and the whole stem can die back.
CONTROL: When watering, avoid wetting flower buds if problems have occurred before (Cultural).
If spotted very early, it may be possible to peel back the sealed outer petals, allowing the bud to bloom normally. Otherwise, cut off affected buds to the healthy part of the stem (Physical).
Describe how plants are affected by Fasciation, along with any methods of preventing and/or ameliorating potential damage.
DAMAGE: Condition where the plant stem, leaf or flower grows abnormally flatter and wider than would otherwise be expected. Limited understanding of causes, but could occur due to a disturbance of the stem apex or bud.
CONTROL: No known controls because reasons for occurrence unknown.
