Environment and ornamental horticulture Flashcards
Climate factors which affect ornamental plants
Climatic factors involves:
Light
Temperature
Humidity
Precipitation
Fog
Wind
Light
Light is an essential factor for any plant growth.
When determining the effect of light on plant growth there are three areas to consider:
Light intensity-
Light intensity rapidly decreases as the distance from the light source increases.
Intensity of light affects photosynthesis, phototropism, respiration and stomatal opening.
It also affects stem length, leaf color and flowering.
Light intensity requirements differ in plants.
High intensity: rose, carnation, most of annuals.
Low intensity: ferns, anthuriums, most of foliage plants.
Intensity of light measured in lux or foot-candles (ft.c).
Type of Plant-
Shade plant (500-1000 ft.c)
Plant which needs low light intensity and do not grow under direct sun
Ferns, Ficus, Philodendrons, Pothos, Schefflera, Begonia
Shade and sun plants (1000-3000 ft.c)
Plants which grows well under shade and direct sun for shorter periods.
Orchids, Sanseveria, Pepromia, English Ivy, Gloxinia
Partial shade and sun plants (2000-8000 ft.c)
Plants which require moderately high light intensity, grow under light shade or direct sunlight.
Gardenia, Magnolia, Abelia
Direct sun plants(3000-8000 ft.c)
Plants which need high light intensity and grow well under direct sun.
Rose, Carnation, Chrysanthemum, Gladiolus, Lantana, Poinsettia, Lily, Antirrhinum
Light duration -
Increased light duration allows the plant to make sufficient food to survive and grow.
However, plants require some period of darkness to properly develop and should be exposed to light for no more than 16 hours per day.
When a plant gets too much direct light, the leaves become pale, sometimes burn, turn brown and die.
Additional lighting can be supplied with either incandescent or fluorescent lights.
Florigen is the hormone which induces flowering.
Gibbrellic acid promotes flowering in long day plants.
Light quality.-
The quality of light detonates the length of waves and thus its color.
Phytochrome is the pigment widely distributed in plats in minute quantities and it absorbs light.
Phytochrome has been identified in roots, coleoptiles, stems, cotyledons, petioles, leaf blade, vegetative buds, floral tissues, seeds, developing fruits of higher plants.
Visible light is the total energy received from the light source observed by the human eye which extends from 390-760 nm.
The components of visible light influences the rate of plant growth.
Green Light- initiation of growth
Blue and red light - satisfactory growth
Effective wavelength for different photo biological processes:
Photosynthesis –Blue (400-450 nm) and red (625-700 nm)
Photoperiodic response- Red (625-700 nm) and far red (700-850 nm)
Phototropic response- Blue (400-450 nm)
Foliage plants responds well in higher levels of blue light than red light.
Temperature
Temperature plays an important role in plants physiological and biochemical reactions.
Most plants tolerate normal temperature fluctuations.
Most flowering plants prefer the daytime temperature range between 21 to 27°C , but grow best when night time temperatures range from 10 to 20°C.
Lower night time temperatures help the plant recover from moisture loss, intensify flower color and prolong flower life.
Extreme low and high temperature will lead to browning, bleaching, puckering, withering, discoloration, scorching, die-back, spindly appearance and foliage damage or drop.
Cool night time temperatures are more desirable for plant growth than high temperatures.
. Humidity
Atmospheric humidity is important to modify moisture loss and temperatures.
Methods to increase relative humidity are:
1. Humidifier: it can be attached to the heating or ventilating system for indoor and protected house plants.
2. Gravel trays with a constant moisture level: it can be placed under pots or containers.
As the moisture around the pebbles evaporates, the relative humidity in the vicinity of the plants will be increased.
- Grouping plants close together.
- Misting the foliage of plants is not generally recommended because of the increased potential for spreading diseases.
If a mist is used, it should be applied early in the day so that leaves will dry before the onset of cooler night time temperatures
Precipitation or rainfall
Main source of water in open fields.
Maximum rainfall is lost in evaporation and runoff.
Minimum is absorbed from soil by plant root hairs.
Total amount of rainfall received and its distribution in different season is essential to estimate minimum amount of irrigation required by plants.
a. Arid and semi-arid regions: receive less rainfall and needs supplement irrigation.
Cacti and succulents, rose, gladioli and some shrubs grow in this region.
b. Humid areas: receive sufficient rainfall and needs supplement irrigation for high yield.
Orchids, some shrubs, foliage plants, tuberose, marigold, ferns and bromeliads grow in this area.
Fog
Source of moisture for plant growth.
Supplies moisture to leaf surface and reduce evapotranspiration rate.
In winter, fog can keep the bud of trees close to the air temperature and cause winter chilling.
Wind
a. Beneficial effects are:
Ease pollen and seed dispersal
Cool the plants
Protect plants from stagnant atmosphere
Deter plant diseases
b. Negative effects
High prevailing wind such as tornadoes, hurricanes damage shrubs and trees.
Low intensity wind damage leaves, branches and deform plants.
Retard plant growth by accelerating transpiration, CO2 uptake and decreasing shoot elongation.
Fences, greenhouses and other structures of the garden are affected by strong winds.
Wind may discourage beneficial insects and make it difficult to check pests, diseases and weeds as spraying is dangerous in windy climate.
Nutrient management in ornamental plants
a. Primary nutrients
Nitrogenous fertilizers: nitrate, ammonic, ammonic and nitrate, amide.
Phosphatic fertilizers: monophosphate, diphosphate, triphosphate.
Potassic fertilizers: Muriate of potash, potassium sulphate.
b. Bulky organic manures
The bulky organic manures are organic in nature and required in huge amounts. They supply:
i) plant nutrients in small quantities.
ii) organic matter in large quantities.
E.g. FYM, Composts, Green manures, Sewage sludge.
c. Beneficial elements
Beneficial elements or potential micronutrients: the elements for which its essentiality for growth and metabolism are not well established but are shown to exert beneficial effects at very low concentrations.
They affect the uptake, translocation and utilization of the essential elements.
They may be essential only for certain plant species or under specific conditions.
Examples are silicon, vanadium, nickel, cobalt, selenium, sodium and aluminium.
Assessment of soil fertility
Experiment: field trials, pot culture, use of indicator plants, nutrients injections and foliar spray.
Microbiological tests: Azotobacter plaque test, Aspergillus niger test.
Chemical test: soil test, plant tissue test, soil analysis, plant analysis.
Visual observation: Plant deficiency symptoms, soil deficiency symptoms.
Methods of fertilizer application
Broadcasting: for uniform basal or topdressing application.
Placement: placed before sowing below the seeds.
In situ application: practiced through drilling, band placement and pallet application.
Foliar application: spraying of solution at low concentrations (2-3%) on leaves.
Water management in ornamental plants
Watering time, quantity and quality of water impact plant quality, shelf-life.
It is associated with plant growth which includes
Plant Species: succulent plants requires less water, Junipers are extremely drought-tolerant, annuals, herbaceous perennials, azaleas and rhododendrons need more water.
Size of Plant: plants with large succulent leaves may need more water. Ornamentals that are half grown, but in the midst of vigorous growth need more water than plants that are mature.
3. Size, Shape and quality of Container.
4. Type of growing medium: the water holding capacity of a growing medium is dependent on the types of components from which it is made. Peatmoss-based media typically hold more water than those made from wood bi-products. Most organic growing media has a waxy outer covering that can repel water if it becomes extremely dry.
5. Environmental conditions
Plants should be watered immediately after transplanting.
Soil should be soaked to a depth of 15-30 cm.
Some ornamentals are very drought tolerant and should avoid overwatering. E.g. peony, hollyhock, lavender, baby’s breath, coneflower, dianthus , butterfly bush.
The best time to water is at evening or in the early morning. Water applied during midday can be lost to evaporation accelerated by the sun.
In extremely dry media, plants can also be flooded to water from the bottom of the container.
Bottom watering provides uniform distribution of water but can cause root diseases if the plant is left flooded too long.
Most ornamental plants in the landscape, once they are established, can go days or even weeks without supplemental irrigation.
Role of growth regulators
Propagation-
Auxin promotes root growth semi hard and hard wood cuttings of ornamental plants
Most commonly used auxins in promoting rooting are
Indolebutyric acid (IBA)
Naphtaleneaceticacid (NAA)
Indoleacetic acid (IAA)
Use of synergists used in combination with auxins induces better rooting than auxin alone.
Hydro benzoic acid and salicylic acid + IBA, IAA, NAA= Better rooting in ornamental shrubs.
Seed and bulb production
Plant height control
Regulation of flowering
Removal of apical dominance
Prolonging the cut flower life
Prevention of sprouting of nursery stock during storage
Herbicide
