Alternative growing media
In addition to open ground or greenhouse borders, plants may be grown in pots, troughs, bags and other containers where restricted rooting makes more critical demands on the growing medium for air, water and nutrients. Soil is an inappropriate material to use in containers as it tends to collapse when kept wet try watering a pot full of soil and note that it is not long before the container is only half full of soil. Soil is replaced in this situation by alternative growing media generally...
Growing medium analysis
The nutrient status of growing media varies greatly between the different materials and within the same materials as time passes. The nutrient levels change because they are being lost by plant uptake, leaching and fixation and gained by the weathering of clay, mineralization of organic matter, and the addition of lime and fertilizers. There are many visual symptoms which indicate a deficiency of one or more essential nutrients see minerals , but unfortunately by the time they appear the plant...
Chapter Plant reproduction
This chapter includes the following topics Figure 7.1 Euphorbia cyparissias 'Fens Ruby' Figure 7.1 Euphorbia cyparissias 'Fens Ruby' Figure 7.2 Range of flowers as organs of sexual reproduction having similar basic structure, but varying appearance having adapted for successful pollination or by plant breeding see chapter 10 a Iris chrysographes 'Kew Black' b Eryngium giganteum, 'Miss Willmott's ghost' c Trollius chinensis 'Golden Queen' d Rosa 'L.D.Braithwaite' e Hemerocallis 'Rajah' f...
Symptoms of disease and physiological disorders
Below in Table 15.2 is a summary of the most important symptoms to help the reader 'home-in' on disease problems and physiological disorders. Table 15.2 Some symptoms of diseases and physiological disorders Table 15.2 Some symptoms of diseases and physiological disorders 2. State the damage caused by three named fungal diseases. 3. Describe the life cycle of one named fungal disease. 4. Describe how the life cycle in the above fungal example is related to its control. 5. Describe the available...
fertilization
This chapter includes the following topics with additional information on the following Compatability and incompatibility Figure 10.1 Bees and other pollinating insects are attracted to large, colourful flowers 133 Figure 10.1 Bees and other pollinating insects are attracted to large, colourful flowers 133
The brown rat Rattus norvegicus
The brown rat, also called the common rat, is well known by its dark-brown colour, blunt nose, short ears and long, scaly tail. Damage. Its diet is varied it will eat seeds, succulent stems, bulbs and tubers, and may grind its teeth down to size by the unlikely act of gnawing at plastic piping and electric cables. A rat's average annual food intake may reach 50 kg, a large amount for an animal weighing only about 300 g. Life cycle. This species has considerable reproductive powers. The female...
Fertilization 1
After entering the ovule, the male nucleus fuses with the female nucleus, their chromosomes becoming intimately associated. The term 'gamete' is used to describe the agents, both male and female, that are involved in fertilization. In animals, the gametes are the eggs and sperms. In plants, they are the ovules and pollen. Fertilization. The union of male and female gametes to produce a zygote fertilized ovule . Incompatible, in relation to fertilization, is a genetic mechanism that prevents...
Other aspects of weed biology
Particular soil conditions may favour certain weeds. Sheep's sorrel Rumex acetosella prefers acid conditions. Mosses are found in badly drained soils. Knapweed Centaurea scabiosa competes well in dry soils. Common sorrel Rumex acetosa survives well on phosphate-deficient land. Yorkshire fog grass Holcus lanatus invades poorly fertilized turf. Nettle and chickweed prefer highly fertile soils. The growth habit of a weed may influence its success. Chickweed and slender speedwell produce horizontal...
Photoperiodism
Photoperiodism is a term used to describe the plants various responses to day length, explained here in terms of flowering other responses include bud dormancy and leaf fall. Many plant species flower at about the same time each year, e.g. in the UK Magnolia stellata in April, Philadelphus delavayi in June and chrysanthemum in September. In many cases, flowering is in response to the changing day length, which is the most consistent changing environmental factor, in comparison with above-ground...
Plant form
Most plant species at first sight appear very similar since all four organs, the root, stem, leaf and flower, are present in approximately the same form and have the same major functions. The generalized plant form for a dicotyledonous and a monocotyledonous plant can be seen in Figure 5.2 . Internode with a leaf sheath enclosing the stem inside Tiller emerging from near ground level Figure 5.2 Generalized plantform a monocotyledon b dicotyledon Internode with a leaf sheath enclosing the stem...
Divisions of the plant kingdom
Figure 4.2 Four multicellular plant divisions horsetail with horticultural significance Figure 4.2 Four multicellular plant divisions horsetail with horticultural significance Mosses and liverworts. Over 25 000 plant species which do not have a vascular system see p92 are included in the divisions Bryophyta and Hepatophyta. They have distinctive vegetative and sexual reproductive structures, the latter producing spores that require damp conditions for survival. Many from both divisions are...
Respiration
In order that growth can occur, the food must be broken down in a controlled manner to release energy for the production of useful structural substances such as cellulose, the main constituent of plant cell walls, and proteins for enzymes. This energy is used also to fuel cell division and the many chemical reactions that occur in the cell. The energy requirement within the plant varies, and reproductive organs can respire at twice the rate of the leaves. Also, in apical meristems, the...
Fertilizer recommendations
The results of the growing medium analysis are interpreted with the appropriate nutrient requirement tables to determine the actual amount of fertilizer to apply. These tables usually have growing medium nutrient status indices to aid interpretation and results are normally given in kg of nutrient per hectare or grams of nutrient per square metre Table 21.4 . In some cases the amount of named fertilizer required is stated if another fertilizer is to be used to supply the nutrient the quantity...
Airfilled porosity AFP
The importance of supplying water to plants in a restricted root volume is usually understood, but the difficulties associated with achieving it whilst maintaining adequate air-filled porosity AFP are less well appreciated. Roots require oxygen to maintain growth and activity. As temperatures rise the plant requires more, but the amount of oxygen that is dissolved in water decreases. Even in cool conditions, the oxygen that can be extracted from the water provides only a fraction of the roots...
Forecasting
Not only is there an interest in weather forecasting in order to plan operations such as cultivations, planting, frost protection, etc., but also for predicting pest and disease attacks, many of which are linked to factors such as temperature and humidity. Examples of outbreaks and methods of predicting them, such as critical periods that are used to predict potato blight. A range of instruments in an agro-meteorological weather station are used to measure precipitation, temperature, wind and...
Cell division
When a plant grows the cell number increases in the growing points or apical and lateral meristems of the stems and roots see p93 . The process of mitosis involves the division of one cell to produce two new ones. The genetic information in the nucleus is reproduced exactly in the new cells to maintain the plant's characteristics. Each chromosome in the parent cell produces a duplicate of itself, thus producing sufficient material for the two new daughter cells see Figure 6.3 . A delicate,...
Budding and grafting
Grafted plants are commonly used in top-fruit, grapes, roses and amenity shrubs with novel shapes and colours. Rootstocks resistant to soil-borne pests and disease are sometimes used when the desired cultivars would succumb if grown on their own roots, e.g. grapevines, tomatoes and cucumbers grown in border soils. Grafting is not usually attempted in monocotyledons, since they do not produce continuous areas of secondary cambium tissue suitable for successful graft-unions. In top fruit,...
Stages in succession
Referring now to secondary succession, there is commonly observed a characteristic sequence of plant types as a succession proceeds. The first species to establish are aptly called the 'pioneer community'. In felled woodland, these may well be mosses, lichens, ferns and fungi. In contrast, a drained pond will probably have Sphagnum moss, reeds and rushes, which are adapted to the wetter habitat. The second succession stage will see plants such as grasses, foxgloves and willow herb taking over...
Nitrogen
Nitrogen is taken up by plants as the nitrate and, to a lesser extent, the ammonium ion. Nitrates and ammonium ions are utilized in the plant to form protein. Plants use large quantities of nitrogen it is associated with vegetative growth. Consequently large dressings of nitrogen are given to leafy crops, whereas fruit, flower or root crops require limited nitrogen balanced by other nutrients to prevent undesirable characteristics occurring. Although plants live in an atmosphere largely made up...
Movement of water up the stem
Three factors contribute to water movement up the stem root pressure by which osmotic forces see p122 push water up the stem to a height of about 30 cm. This can provide a large proportion of the plant's water needs in smaller annual species capillary action attraction of the water molecules for the sides of the xylem vessels , which may lift water a few centimetres, but which is not considered a significant factor in water movement transpiration pull is the major process that moves soil water...
Woodlouse Armadillidium nasutum
The damage is confined mainly to stems and lower leaves of succulent glasshouse crops such as cucumbers, but occasionally young transplants may be nipped. A relative of marine crabs and lobsters, the woodlouse has adapted for terrestrial life, but still requires damp conditions to survive. In damp soils it may number over a million per hectare, and greatly helps the breakdown of plant debris, as do earthworms. In greenhouses, where plants are grown in hot, humid conditions, this species may...
The bullfinch Pyrrhulapyrrhula
This is a strikingly-coloured, 14 cm long bird, characterized by its sturdy appearance and broad bill. The male has a rose-red breast, blue-grey back and black headcap. The female has a less striking pink breast and yellowish-brown back. Damage. From April to September the bird progressively feeds on seeds of wild plants, e.g. chickweed, buttercup, dock, fat hen and blackberry. From September to April, the species forms small flocks that, in addition to feeding on buds and seeds of wild...
Vegetable production
The choice of cultivar is an important decision that has to be made before growing starts. There are many possibilities for each crop, but a major consideration is the need for uniformity. Where this is important, e.g. for 'once over harvesting' or uniform size, then F1 hybrids are normally used even though they are more expensive see p144 . Required harvesting dates affect not only sowing dates but the selection of appropriate early, mid-season or late cultivars. Other factors for choice...
Define the following terms family genus species subspecies ephemeral biennial
Allaby, M. 1992 . Concise OxfordDictionary ofBotany. Oxford University Press. Baines, C. and Smart, J. 1991 . A Guide to Habitat Creation. Packard Publishing. Brown, L.V. 2008 . AppliedPrinciples ofHorticultural Science. 3rd edn. B utterworth-Heinemann. Dowdeswell, W.H. 1984 . Ecology, Principles andPractice. Heinemann Educational Books. Heywood, V.H. et al. 2007 . Flowering Plant Families ofthe World. Firefly Books. Hillier Gardener's Guide 2005 . PlantNames Explained. David and Charles....
Crop rotation
Some important soil-borne pests and diseases attack specific crops, such as potato cyst nematode on potato and club root on cruciferous plants. As they are soil-borne, they are slow in their dispersal, but are difficult to control. By the simple method of planting a given crop in a different plot each season, such pests or diseases are excluded from their preferred host crop for a number of years, during which their numbers will slowly decline. A gardener often creates five or six plots...
Other effects on soil
Beneficial soil organisms see p320 are affected by soil acidity and liming. A few soil-borne disease-causing organisms tend to occur more frequently on lime deficient soils see clubroot , whereas others are more prevalent in well-limed soils. Calcium sometimes improves soil structure and soil stability. It is probable that this is mainly because it encourages root activity and creates conditions favourable for decomposition of organic matter, yielding humus see p326 . Free lime in clay soils...
The classification of plants
Any classification system involves the grouping of organisms or objects using characteristics common to members within the group. A classification can be as simple as dividing things by colour or size. Fundamental to most systems and making the effort worthwhile is that the classification meets a purpose has a use. This is generally to make life simpler such as to find books in a library they can be classified in different, but helpful ways, e.g. by subject or date or particular use. Terms that...
Photosynthesis
The following environmental requirements for photosynthesis are explained in detail below water see also Chapters 9 and 10 . All living organisms require organic matter as food to build up their structure and to provide chemical energy to fuel their activities. Whilst photosynthesis is the crucial process, it should be remembered that a multitude of other processes are occurring all over the plant. Proteins are being produced, many of which are enzymes necessary to speed up chemical reactions...
Benefits of organic matter
Organic matter plays an important part in the management of soils. The main benefits are living organisms in the soil play their part in the conversion of plant and animal debris to minerals and humus Rhizobia and Azotobacter spp. fix gaseous nitrogen plant roots, earthworms and other burrowing organisms improve the soil structure many types of bacteria play an important role in the detoxification of harmful organic materials such as pesticides and herbicides dead organic matter is food for...
Characteristics of propagation from vegetative parts
Vegetative propagation is used in horticulture to produce numbers of plants from a single parent plant. This group of plants, or clone, is an extension of the parent plant and therefore all will have the same genetic characteristics. The greatest advantage for horticulturists is to be able to reproduce a cultivar in which all the resulting plants exhibit consistent characteristics. There are some cultivars that can only be reproduced by vegetative means. Seeds produced without fertilization...
Raspberry beetle Byturus tomentosus
The developing fruit of raspberry, loganberry and blackberry may be eaten away by the 8 mm long, golden-brown larvae of this pest. Only one life cycle per year occurs, the larva descending to the soil in July and August, pupating in a cell from which the golden-brown adult emerges to spend the winter in the soil. The adult female lays eggs in the host flower the following June. Spread is by means of the flighted adult. Control. Since the destructive larval stage may enter the host fruit and...
Deficiencies
Simple deficiencies are those in which too little of the nutrient is present in the growing medium. Most soils have adequate reserves of trace elements, so simple deficiencies in them are uncommon, especially if replenished with bulky organic matter. Sandy soils tend to have low reserves and so too have several organic soils from which trace elements have been leached. In horticulture simple deficiencies of trace elements are mainly associated with growing in soil-less composts which require...
Bacterial canker Pseudomonasmorsprunorum
Damage. This disease affects the plant genus Prunus that includes ornamental species, plum, cherry, peach and apricot. Symptoms typically appear on the stem as a swollen area exuding a light brown gum see Figure 15.18 . The angle between branches is the most common site for the disease. Severe infections girdling the stems cause death of tissues above the infection, and the resulting brown foliage can resemble the damage caused by fireblight. In May and June, leaves may become Figure 15.18...
Sowing and aftercare in protected environments
The ideal conditions for raising plants from seed can be achieved in a protected environment such as a glasshouse or cheaper alternatives such as polythene tunnels or cold frames see p16 . Most seeds grown in protected culture are sown into containers see Figure 12.2 Figure 12.2 Range of containers for growing plants a traditional clay pots b standard seed tray and half tray c standard plastic pots in range of sizes, compared with d 'long toms' and e half pots f biodegradable pots g compressed...
Removal of infected plant material
With rapid-increase problems, such as peach-potato aphid and white rust of chrysanthemum fungus in greenhouses, removal of affected leaves is practicable in the early stages of the problem, but becomes progressively unmanageable after the pest or disease has increased and dispersed throughout the plants. Slow-increase problems, such as Fusarium wilt disease on tomatoes or carnations and vine weevil larvae found damaging roots of plants such as primulas and begonias, may be removed throughout...
Mineral uptake
Minerals are absorbed to form the soil solution see Chapter 21 . The plants take up only water-soluble material so all supplies of nutrients including fertilizers and manures must be in the form of ions charged particles . The movement of the elements in the form of ions occurs in the direction of root cells containing a higher mineral concentration Figure 9.4 Cross-section of Zea mais root showing its structure in the absorption and transport of water and minerals Figure 9.4 Cross-section of...
Stem and bulb eelworm Ditylenchusdipsaci
Damage. The damage caused by this species varies with the crop attacked. Onions show a loose puffy appearance called bloat carrots have a dry mealy rot the stems of beans are swollen and distorted. Narcissus bulbs show brown rings when cut across and their leaves show raised yellow streaks. Life cycle. This species attacks many plants, e.g. narcissus, onions, beans and strawberries. Several strains are known, but their host ranges are not fully defined. The 1 mm long nematodes enter plant...
Centipedes
These animals resemble millipedes, but are much more active. They help control soil pests by searching for insects, mites and nematodes in the soil. This group of organisms, also called eelworms, is found in almost every part of the terrestrial environment, and range in size from the large animal parasites, e.g. Ascaris about 20 cm long in livestock, to the tiny soil-inhabiting species about 0.5 mm long . Non-parasitic species may be beneficial, feeding on plant remains and soil bacteria, and...
Mammal pests
Pest. A mammal, bird, insect, mite or nematode that is damaging to plants. A small selection of important mammal pests is included here. The rabbit Oryctolagus cuniculus The rabbit is common in most countries of central and southern Europe. It came to Britain around the eleventh century with the Normans, and became an established pest in the nineteenth century. Damage. The rabbit may consume 0.5 kg of plant food per day. Young turf and cereal crops are the worst affected, particularly winter...
Wireworm Agriotes lineatus
Damage. This beetle species is commonly found in grassland, but will attack most crops. Turf grass may be eaten away by the larvae wireworms resulting in dry areas of grass. The pest also bores through potatoes to produce characteristic narrow tunnels, while in onions, brassicas and strawberries the roots are eaten. In tomatoes, the larvae bore into the hollow stem. Life cycle. The 1 cm long adult click beetle is brown-black and has the unusual ability of flicking itself in the air when placed...
Soil development
The nature of a new soil regosols is largely determined by the rock minerals from which it is formed, but it continues to undergo changes under the influence of climate, vegetation, topography and drainage. These interact over time to give rise to characteristic soil profiles in different parts of the world. The soils that develop can be described in terms of the characteristics of the different horizons layers that make up the soil profile. The 'O' or 'L' horizon is the organic matter found on...
Potato blight Phytophthorainfestans
This fungus is a member of the Zygomycota division of fungi see p74 . Damage. This important disease is a constant threat to potato production it caused the Irish potato famine in the nineteenth century. The first symptoms seen in the field are yellowing of the foliage, which quickly goes black and then produces a white bloom on the under surface of the leaf in damp weather. The stems may then go black, killing off the whole plant. The tubers may show dark surface spots that, internally, appear...
Other beetle pests
Springtime attack of flea beetle Phyllotreta species on leaves of young cruciferous plants e.g. cabbages and stocks is a serious problem to amateur and professional horticulturist alike see Figure 14.21 . In recent years, four other increasingly common beetle problems have been reported. These are viburnum beetle on Viburnum opulus, V. tinus and V. lantana, rosemary leaf beetle Chrysolina americana on lavender, rosemary and thyme, red lily beetle Lilioceris lilii on lilies, and asparagus beetle...
Alternatives to peat
Whilst peat remains a popular choice as a compost ingredient, great efforts are being made to find alternatives in order to preserve the wetland habitats where peat is harvested. A list of some of the materials used is given in Table 22.1. Much progress has been made by using suitably processed bark or coconut fibre in composts. Along with several other organic sources they are waste-based and recycling them helps in conserving resources. All such alternatives must be free of toxics and...
Migratory plant nematodes
The species of nematodes described above spend most of their life cycle inside plant tissues endoparasites . Some species, however, feed only from the outside of the root ectoparasites . The dagger nematodes e.g. Xiphinema diversicaudatum and needle nematodes e.g. Longidorus elongatus , which reach lengths of 0.4 and 1.0 cm respectively, attack the young roots of crops such as rose, raspberry and strawberry, and cause stunted growth. In addition, these species transmit the important viruses,...
Organic matter levels
The routine laboratory method for estimating organic matter levels depends upon finding the total carbon content of the soil. A simpler method is to dry a sample of soil and burn off the organic matter. After Most topsoil contains between 2 per cent and 5 per cent of organic matter, whereas subsoil usually contains less than 2 per cent. The methods give an overall total of soil organic matter excluding the larger soil animals. cooling, the soil can be re-weighed and the loss in 5 weight...
Explain how evaporation and consequent water loss can be controlled in the
Clegg, C.J. and Cox, G. 1978 . Anatomy andActivities ofPlants. John Murray. Ingram, D.S. et al. eds 2002 . Science and the Garden. Blackwell Science Ltd. Mauseth, J.P. 1998 . Botany-An Introduction to Plant Biology. Saunders. Moorby, J. 1981 . Transport Systems in Plants. Longman. Scott Russell, R. 1982 . PlantRoot Systems TheirFunction andlnteraction with the Soil. McGraw-Hill . Sutcliffe, J. 1971 . Plants and Water. Edward Arnold. Sutcliffe, J.F. and Baker, D.A. 1976 . Plant andMineral Salts....
Hydroponics Clay Balls
Sands are gritty to the touch even fine sand has an abrasive feel. Sand is mainly composed of quartz. Although any particle of this size is a sand grain, it is most often quartz because, unlike other minerals, it resists weathering. The shape of the particles varies from the rough and angular sand to more weathered, rounded grains. They are frequently coated with iron oxides, giving sand colours from very pale yellow to rich, rusty brown. Silver sand has no iron oxide covering. Chemically most...
Supervised control
Most plants can tolerate low levels of pest and disease damage without yield reduction, unless the damage is to parts of the plant that become unacceptable such as fruits for the supermarket trade . The term 'economic threshold' is used to summarize this concept. Cucumbers, for example, require more than 30 per cent leaf area affected by red spider mite before economic damage occurs in terms of yield loss. This enables methods of control that depend on some damage being Integrated control...
Artificial control offlowering
A long night may be broken artificially using a technique called night-break lighting. Incandescent tungsten bulbs produce a high proportion of red light and are cheap to run. Hung about 1 m above the crop and spaced to give about 150 lux for four hours ensures that the Pfr730 critical level is not reached. Cyclic lighting saves electricity and uses a series of brief alternating light and dark cycles to replace one continuous break. High pressure sodium lamps are used where they are installed...