7VISUAL SYMPTOMS ON LEAVES When inspecting plants for symptoms of nutrient disorders, compare plants displaying symptoms with normal ones and examine new and older leaves.OLDEST LEAVES: nutrient deficiencies generally appear first in the oldest leaves when nitrogen, phosphorus, potassium, and magnesium are limiting. These nutrients move from one part of the plant to another as needed.YOUNGER LEAVES AND TERMINAL BUDS: show a deficiency when sulfur, iron, calcium, zinc copper, boron, manganese or chlorine are limiting. These nutrients do not readily move about in the plant.
8Nutrients Deficiency Symptoms on Leaves The most common symptoms of nutrient deficiency are stunted growth and leaf discoloration. The position of the symptoms (distal, basal or intermediate) depends on the mobility of the nutrient inside the plant (young leaves competing with oldest leaves)
15Nutrients Removal: Apple N (KG)P (KG)K (KG)Mg (Ca)Ca (KG)Nutrient removed per ton apple0.50.11.10.05Nutrient removal at 50 tons/ha255552.5Nutrient incorporated into trees/ha20415245Total nutrient consumed 50t/ha9704.547.5
17Nitrogen Nitrogen is a building block of plant protein. It is an integral part of chlorophyll and is a component of amino acids, nucleic acids and coenzymes.Most nitrogen in the soil is tied up in organic matter. It is taken up by plants as nitrate (NO3-) and ammonium (NH4+) ions from inorganic nitrate and ammonium compounds.These compounds can enter the soil as a result of bacterial action (nitrogen fixation), application of inorganic nitrogen fertilizer, or conversion of organic matter into ammonium and nitrate compounds.Not all nitrates in the soil are taken up by plants.Nitrates can be leached beyond the root zone in sandy soils or converted to nitrogen gas in wet, flooded soils.Nitrogen fixation (from atmosphere) by soil microbes immobilizes nitrogen, making in available for later use by plants.
29PhosphorusPlants use phosphorus to form the nucleic acids DNA and RNA and to store and transfer energy.Phosphorus promotes early plant growth and root formation through its role in the division and organization of cells.Phosphorus is essential to flowering and fruiting and to the transfer of hereditary traits.Phosphorus is adsorbed by plants as H2PO4-,HPO4-2 or PO-3, depending upon soil pH.The mobility of phosphorus in soil is low, and deficiencies are common in cool, wet soils.Phosphorus should be applied to fields and gardens before planting and should be incorporated into the soil. This is especially important for perennial crops.Application rates should be based on soil testing.
33PotassiumPotassium is necessary to plants for translocation of sugars and for starch formation.It is important for efficient use of water through its role in opening and closing small apertures (stomata) on the surface of leaves.Potassium increases plant resistance to diseases and assists in enzyme activation and photosynthesis.It also increases the size and quality of fruits and improves winter hardiness.Plants take up potassium in the form of potassium ions (K+).It is relatively immobile in soils but can leach in sandy soils.Potassium fertilizer should be incorporated into the soil at planting or before.Application rates should be based on a soil test.
35CalciumCalcium provides a building block (calcium pectate) for cell walls and membranes and must be present for the formation of new cells.It is a constituent of important plant carbohydrates, such as starch and cellulose.Calcium promotes plant vigor and rigidity and is important to proper root and stem growth.Plants adsorb calcium in the form of the calcium ion (Ca+).Calcium needs can be only determined by soil test.In most cases calcium requirements are met by liming the soil.Potatoes are an exception; use gypsum (calcium sulfate) on potatoes to avoid scab disease if calcium is needed.Gypsum provides calcium to the soil but does not raise the pH level of the soil.Keeping pH low helps prevent growth of the bacteria that cause scab disease.
37MagnesiumMagnesium is a component of the chlorophyll molecule and is therefore essential for photosynthesis.Magnesium serves as an activator for many plant enzymes required for sugar metabolism and movement and for growth processes.Plants take up magnesium as the Mg+2 ion.
40Zinc Zinc is an essential component of several enzymes in plants. It controls the synthesis of indoleacetic acid (ANA), an important plant growth regulator, and it is involved in the production of chlorophyll and protein.Zinc is taken up by plants as the zinc ion (Zn+2).Zinc deficiencies are more likely to occur in sandy soils that are low in organic matter.High soil pH, as in high-lime soils, the solubility of zinc decreases and it becomes less available.Zinc and phosphorus have antagonistic effects in the soil. Therefore zinc also becomes less available in soils that are high in phosphorus.Wet and cold soil conditions can cause zinc deficiency because of slow root growth and slow release of zinc from organic matter.
43Iron Iron is taken up by plants as ferrous ion (Fe+2). Iron is required for the formation of chlorophyll in plant cells.It serves as an activator for biochemical processes such as respiration, photosynthesis and symbiotic nitrogen fixation.Turf, ornamentals and certain trees are especially susceptible to iron deficiency (Quince, Peach, Kiwi)Symptoms of iron deficiency can occur on soils with pH greater than 7.0.Specific needs for iron can be determined by soil test, tissue test and visual symptoms.
49Genetic EngineeringThere are two main techniques used:
50Products of Plant Biotechnology Delayed ripening tomatoesHerbicide resistant canola, soybeans, cotton, and other cropsInsect resistant corn, potatoes, and other cropsGolden Rice (vitamin A and beta-carotene enriched)
52Plant Hormones What is a hormone? It must meet these criteria: An endogenous organic compoundActive at very low concentrationsProduced in one tissueTransported from the site of synthesis to the tissue in which it actsAffects growth, development and physiological responses (it is not a nutrient or vitamin)
54Auxin Controls cell elongation and expansion Involved in phototropic and gravitropic responsesgrowth of shoots towards lightdownward growth of roots (response to gravity)Suppresses growth of axillary budsStimulates root initiation and growthStimulates fruit growth
62Branching of shoots Where do branches come from? Develop from axillary budsBuds are present within leaf axils on the stem (stems have buds)
63Branching of shootsAxillary buds contain a meristem that is usually inactiveapical dominance growth at the apex suppresses growth of lateral shootsWhy are axillary buds normally dormant?Active apical budDormantaxillarybuds
64Branching of shootsAuxin is produced in shoot apex and transported down the plant stemThe concentration of auxin is high close to the shoot apexAuxin concentration is lower in tissues further away from the apexAuxin producedin shoot apexHigh [auxin]Low [auxin]
65Branching of shootsAuxin producedin shoot apexHigh [auxin]Low [auxin]High concentrations of auxin suppress growth of axillary buds near the apexFurther away from the apex, where the auxin concentration is lower, growth of axillary buds is not inhibitedThese buds develop and grow, forming branches
66Branching of shootsThe strength of apical dominance varies among plant speciesStrong apical dominance results in plants with a dominant primary shoot
67Branching of shootsThe strength of apical dominance varies among plant speciesWeak apical dominance leads to a more branched plant form
68Pinching promotes branching Apical bud is removedAuxin is not presentAxillary buds developPinching removes the apical meristem, the source of auxinWith no auxin coming from the apex, axillary buds develop giving rise to a bushier plant
69Tree topping - a (bad) example of loss of apical dominance Tree topping removes the shoot apex/apicesAxillary buds grow and develop into long, weak sproutsTrees that are topped are permanently damaged and lose much visual appeal
71Synthetic auxins: practical applications Stimulate rooting of cuttings in plant propagationControl fruit set - the number of fruit that develop after pollination2,4-D, a synthetic auxin, is used as a herbicide to kill dicot weeds in lawns and cereal crops (monocot plants)
73CytokininsWhen a terminal bud is removed, the inhibitory effect of auxin on the lateral buds is removed, and the stimulating effect of cytokinins activates the axillary buds
74Branching of roots Branch roots are initiated in the pericycle Layer of cells between the endodermis and vascular cylinder
75Secondary growth Increased diameter of stems and roots Primarily due to activity of the cambiumLayer of meristem cells between the phloem and xylem
76Secondary growthIn woody plants, division of cells in the cambium gives rise to a new layer of xylem cells each yearXylem becomes lignified and permanent, visible as annual growth rings
77Secondary growthPhloem is not a permanent tissue but is replaced each yearCambium provides cells for new phloem tissue
78Manipulating cytokinins Promotes shoot growth in tissue cultureUsed to alter fruit shape
79Gibberellins (GA) Stimulate stem elongation many dwarf varieties are gibberellin-deficient or unable to respond to gibberellinControl metabolism of stored reserves during seed germination
80Foolish SeedlingIs a condition found in rice plants where they grow tall and weak, often falling over and not producing any rice. It is caused by a fungus of Giberella sp.
81GibberellinsThey are produced in the tips of shoots and roots, young leaves and embryos.
82Manipulating gibberellins Height control - keeping plants smallflowering pot plants, e.g. Easter lilybedding plantsIncreasing size of grapes by making looser bunches (Thompson seedless)Promotes desired elongated shape of 'Red Delicious' apples
83Abscisic Acid (ABA) Stimulates closure of stomata Promotes maturation and dormancy of seedsInhibits seed germinationRegulates many responses to adverse environmental conditionsPlants under stress frequently have elevated levels of abscisic acid
85Ethylene Regulates ripening of many fruits Controls senescence of many flowersTriggers abscission of leaves and fruitsIncreases proportion of female flowers in cucurbits (cucumber, zucchini, pumpkin)Regulates shoot growth during germination
87Manipulating ethylene Ethylene applicationStimulates flowering (pineapples)Initiates ripening (bananas, tomatoes)Promotes fruit drop (cherries)Ethylene inhibitionDelays ripening (long term apple storage)Delays flower senescence (silver treatment of cut flowers)
88Summary Growth results from Cell divisionExpansion or elongationDifferentiationGrowth in plants occurs in specialized areasMeristems are the sites of cell division and are the source of new cells for plant growth
89SummaryCell expansion and differentiation occur in regions behind meristemHormones play critical roles in plant growthHorticulturists control the shape and form of plants by manipulating growth and development
96Manipulating plant growth: Pruning Fruit trees are pruned to develop an efficient structure to bear fruit and to maximize interception of lightbefore pruningafter pruning
97Manipulating plant growth: Training Plants are trained for both decorative and practical reasons
98Manipulating plant growth: Shaping Trees and shrubs are shaped for commercial and aesthetic reasonsChristmas treesTopiary
99Two processes at work in plant growth At the cellular level there are two processes that contribute to plant growthCell divisionThe source of new cells for growth of an organ or tissuedivisiondivision2
100Two processes at work in plant growth Cell enlargementAn increase in the volume of a cellThe combined effects of both processes lead to the growth of plant organs and to the overall increase in size of a plantenlargement2
101Primary GrowthGrowth that leads to increased height of shoots or length of rootsGrowth occurs at the apices of these organsCells in the apical meristems divide and provide the supply of cells for growth
102Cell differentiationAs cells “move away” from the apex they differentiate into specialized types of cellsEvery cell has the genetic potential to develop into any of the specialized cell types in a plant
103DifferentiationDifferentiated cells don’t normally switch to another cell typeAfter plant cells differentiate they are fixed in placesurrounded by rigid cell walls, glued together
104Manipulating plant hormones Horticulturists use synthetic hormones, hormone analogs and inhibitors of hormone action to manipulate many aspects of plant growth and developmentThese compounds are called plant growth regulators