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Botany for gardeners 2014


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This lecture was given in February, 2014 as part of the California native plant gardening series ‘Out of the Wilds and Into Your Garden’

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Botany for gardeners 2014

  1. 1. Out of the Wilds and Into Your Garden Gardening with Western L.A. County Native Plants Project SOUND – 2012 (our 8th year) © Project SOUND
  2. 2. Botany for S. CA Gardeners Key Botanic Concepts to Improve Your Gardening C.M. Vadheim and T. Drake CSUDH & Madrona Marsh Preserve Madrona Marsh Preserve February 1 & 4, 2014 © Project SOUND
  3. 3. California – the land of extremes      Latitude Elevation Temperature Precipitation Soil type, content That’s part of the reason why my have so many unique native plants © Project SOUND
  4. 4. Botany: the study of plants (huge subject area) Today’s talk I. Names, descriptions and taxonomy II. Seeds A. B. C. How they develop Dispersal Germination III. How plants grow IV. Water & nutrients from the environment © Project SOUND
  5. 5. Hollyleaf Redberry – Rhamnus ilicifolia © 2003 BonTerra Consulting © Project SOUND
  6. 6. Scientific names: why do we need ‘em?  They are (or at least should be) universal  They are unique to a given taxon – unlike common names like ‘Wild pea’ or ‘Wild sunflower’  The name sometimes describes characteristics of the plants [ilicifolia = holly-like leaves] or honors the person who discovered them © 2006 Steve Matson  The name (should) reflect the evolutionary relationships between it and other taxa Rhamnus ilicifolia © Project SOUND
  7. 7. Taxonomy & Systematics: grouping & naming  Taxonomy: science that finds, identifies, describes, classifies, and names plants  Three goals:  Identification : identifying an unknown plant by comparison with previously collected  Classification: placing known plants into groups or categories to show some relationship.  Description : formal description of a new species, usually in the form of a scientific paper  Systematics: the science of relationships between plants and their evolution, especially at the higher levels  Classical (morphological) systematics – based on similarities in plant physical characteristics (how plant looks; chemical similarities; etc.)  Molecular systematics – based on similarities in genetic material The two are highly interrelated – both aim to better understand and reflect the true relationships between different plants © Project SOUND
  8. 8. Kingdom Subkingdom Superdivision Division Class Subclass Order Family Genus Species © 2005 James M. Andre Plantae – Plants Tracheobionta – Vascular plants Spermatophyta – Seed plants Magnoliophyta – Flowering plants Magnoliopsida – Dicotyledons Rosidae Rhamnales Rhamnaceae – Buckthorn family Rhamnus L. – Buckthorn Rhamnus ilicifolia Kellogg – Hollyleaf redberrry © Project SOUND
  9. 9. Resources to help the confused gardener  USDA Plants Database: © Project SOUND
  10. 10. The importance of higher taxa: insight  Family Rhamnaceae © 2005 James M. Andre © 2003 BonTerra Consulting  Mostly trees/shrubs  Simple leaves, with stipules  Flowers usually small, inconspicuous [exception: Ceanothus spp.]  Fruits are mostly berries, fleshy drupes or nuts – mostly dispersed by mammals and birds.  Chiefly used as ornamental plants and as the source of many brilliant green and yellow dyes © Project SOUND
  11. 11. The importance of higher taxa: insight  Genus Rhamnus © 2002 Kristiaan Stuart Spiny redberry Rhamus crocea Common name: Buckthorn Usually deciduous – CA has evergreen species Fruit: berrylike, fleshy (edible?) Wide light tolerance range Generally drought tolerant once established May be slow to get started – then easy to grow May cause mild dermatitis Medicinal: prepared bark - purgative; laxative Invasive potential: in Eastern U.S., exotic buckthorns (R cathartica; R. frangula) tend to form dense, even-aged thickets, crowding and shading out native shrubs and herbs  California members:           Rhamnus (now Frangula) californica – CA Coffeeberry  Rhamnus crocea – spiny redberry © Project SOUND
  12. 12. The scientific name  The generic name is listed first (with its first letter capitalized), followed by a second term, the specific name (or specific epithet) and the name(s) of the first namer  International Code of Botanical Nomenclature – specifies the format and conventions  U.S. Integrated Taxonomic Information System (ITIS) facilitates sharing biologic info. by providing a common framework for taxonomic data Hollyleaf redberry  Sometimes regional experts don’t agree with ITIS Rhamnus ilicifolia Kellogg © Project SOUND
  13. 13. Calflora database: CA plants (native & not) © Project SOUND
  14. 14. What is a species?  Some definitions of species  Biological Species Concept - they cannot interbreed & produce viable offspring; interbreeding studies Lyonothamnus floribundus ssp. aspleniifolius  Morphospecies Concept - they are different morphologically and do not come in contact for interbreeding  Genetic Species Concept – still working on this – how similar must they be to constitute a species?  Practical definition - Practically, biologists define species as populations of organisms that have a high level of genetic similarity.  The field of taxonomy is changing with our increasingly sophisticated tools Lyonothamnus floribundus ssp. floribundus © Project SOUND
  15. 15. California (and other biologic ‘hotspots’) present more challenges  Lots of geographic/topographic variability  Relatively ‘rapid’ environmental changes (since last Ice Age) © 2002 Kristiaan Stuart Rhamnus ilicifolia  Lots of geographically separate populations – are in the process of diverging  In other words, speciation is a ‘work in progress’ Rhamnus crocea © Project SOUND m
  16. 16. Why all the current taxonomic/systematic arguments about CA native plants?  When two species have fully diverged from a common ancestor they will possess the properties commonly associated with independent species:  reproductive incompatibility  distinctive morphology  ecological uniqueness.  During the process of divergence, these properties are gradually acquired in a continuum spanning thousands of years.  When two lineages are in the early stages of speciation it is difficult for biologists holding different species concepts to agree on when there has been enough divergence to declare them as different species. © Project SOUND
  17. 17. What’s a CA native plant gardener to do?  Keep calm – this period of rapid change will end  Nurseries will likely know plants by both old and new name  Use on-line sources  Native Plants at CSUDH  Scientific name - Scientific name key  Common name - Scientific name key  USDA Plants database  Calflora database © Project SOUND
  18. 18. Native Plants at CSUDH © Project SOUND
  19. 19. Use the ‘pages’ on left of screen Name to name lists are here © Project SOUND
  20. 20. The PLANTS database
  21. 21. Implications of plant taxonomy/systematics for the gardener  Precise, scientific names are important:  For scientists – including biomedical scientists working with plant-based medicinal chemicals, insecticides, etc. © 2002 Kristiaan Stuart Rhamnus ilicifolia  For you as a gardener – so you purchase the plant whose characteristics you want  Plant systematics provides insights  Understanding basic characteristics of groups – requirements, susceptibilities, toxicities © Project SOUND
  22. 22. Implications of plant taxonomy/systematics for the gardener  Conservation – importance of conserving local endangered species in gardens, seed banks, etc.  Choice of appropriate plant species – esp. if crosspollination danger [Salvias; Buckwheats]  Evolution in the garden  ‘garden-friendly’ cultivars (including novel hybrids)  Selection and climate change © Project SOUND
  23. 23. Plant anatomy and morphology: describing plants © Project SOUND
  24. 24. Describing plants: what do those terms mean?  Stem: bark gray; branches stiff, generally ascending; twigs glabrous to finely hairy.  Leaf: evergreen; petiole 2–10 mm; blade 20–40 mm, ovate to round, thick, glabrous adaxially, glabrous or hairy, flat to concave abaxially, base rounded, tip obtuse, rounded, or widely notched, margin entire, irregularly toothed, or prickly, veins prominent or not. © Project SOUND
  25. 25. Describing plants: simple leaves Margin Blade tip  Basic anatomy  Petiole  Blade  Stipule  Veins Base  Midrib  Veins  Shape terminology     Overall shape Blade tip Blade base Margins © Project SOUND
  26. 26. Simple vs. compound leaves  Clues:  Look for an axillary bud (just above the midrib)  Look at old (or recently fallen) leaves – the petiole separates cleanly from the branch (due to an abscission layer)  Use plant Family traits – [Pea family (Fabaceae) usually have compound leaves] © Project SOUND
  27. 27. Describing plants: leaf shapes toothed © Project SOUND
  28. 28. Describing plants: what do they mean?  Stem: bark gray; branches stiff, generally ascending; twigs glabrous to finely hairy.  Leaf: evergreen; petiole 2–10 mm; blade 20–40 mm, ovate to round, thick, glabrous adaxially, glabrous or hairy, flat to concave abaxially, base rounded, tip obtuse, rounded, or widely notched, margin entire, irregularly toothed, or prickly, veins prominent or not. © Project SOUND
  29. 29. Botanical terms/concepts & plant identification  Some excellent resources written specifically for the gardener  These 3 books are very good © Project SOUND
  30. 30. Help with terminology  We’ve tried to make using on-line resources easier by bringing together the best in one place – ‘Native Plants at CSUDH’  Books  Allaby, M : Oxford Dictionary of Plant Sciences  Beentje, H : Kew Plant Glossary - an illustrated dictionary of plant terms  On-line:  Several good resources – good for gardeners © Project SOUND
  31. 31. Let ‘Native Plants at CSUDH’ help The ‘Pages’ on the left of the screen provide helpful links to the Project SOUND/Out of the Wilds plant lists(under ‘Plant Lists’), gardening information sheets & plant photos (under ‘Gallery of Native Plants’) © Project SOUND
  32. 32. Gallery of Native Plants – Native Plants at CSUDH There alphabetical name lists: • Scientific name to current sci name • Common name to scientific name © Project SOUND
  33. 33. Native Plant Gallery – Native Plants at CSUDH Click ‘Save’ – then choose to download or save. You’ll be able to click on links © Project SOUND
  34. 34. Help make the ‘Gallery’ even better Send us your pictures of CA native plants growing in garden settings © Project SOUND
  35. 35. Native Plants at CSUDH http://nativeplantscsudh. Just search ‘native plants at csudh’ with your favorite browser © Project SOUND
  36. 36. We’re very familiar with the life stages of animals © Project SOUND
  37. 37. Plants have similar – but different – life stages  Fertilization  Embryogenesis/seed formation  Seed germination/early growth  Juvenile growth (vegetative)  Mature growth (vegetative)  Flowering/Fruiting/seed production  Senescence  Death
  38. 38. Describing plants: what do they mean?  Inflorescence: 1–6-flowered, generally glabrous; pedicel 2–4 mm.  Flower: generally unisexual; hypanthium ± 2 mm wide; sepals 4; petals 0.  Fruit: 2-stoned, 4–8 mm, red. Mark W. Skinner @ USDA-NRCS PLANTS Database © 2002 Kristiaan Stuart © Project SOUND
  39. 39. Inflorescence: grouping/arrangement of flowers Wikipedia has a very good coverage of inflorescence terms © Project SOUND
  40. 40. Flowers are leaves specialized for reproduction  Calyx (whorl of Sepals) – protect/attract  Corolla (whorl of Petals) – attract  Stamen – male sex parts  Filament  Anther – produces pollen  Pistil – female sex parts A ‘perfect’ flower – has all the parts  Stigma – receives pollen  Style – channel  Ovary – contains eggs which become seeds © Project SOUND
  41. 41. How does the pollen get to the stigma?  Falls on it  Physical agents  Wind  Water  Biologic agents (Mother Nature’s cupids)        Bees Flies Butterflies/moths Other insects Hummingbirds Bats Other animals © Project SOUND
  42. 42. Take-home messages: pollination  Getting the pollen to the egg isn’t easy if you’re a plant – and you usually need a little help  The lives of plants and their pollinators are in intimately intertwined What are the likely pollinators of Hollyleaf redberry?  Plants and animal pollinators have evolved together (co-evolution).  Plants usually don’t waste energy on things they don’t really need – the color/scent etc. are there for a reason © Project SOUND
  43. 43. Pollination and Fertilization
  44. 44. What does it take to form a seed? © Project SOUND
  45. 45. The unwritten goal of all living things: reproduce and disperse That’s how species survive through time © Project SOUND
  46. 46. Why the need to disperse?  To decrease unhealthy competition (for light, water, other resources)  To colonize new areas – which may have better resources or other advantages  To increase genetic diversity within the species or population – novel combinations that may confer an advantage © Project SOUND
  47. 47. Dispersal is relatively easy if you have legs or can swim © Project SOUND
  48. 48. Seed dispersal: traveling through space  Dropping to the ground  Catapulted from the dry seed capsule (fruit)  Carried by physical agents  Floating on the wind  Carried by water  Carried by living agents  Hitchhiking on animal fur, feathers or feet  Travelling through a bird or animal for eventual deposition © Project SOUND
  49. 49. Clues to dispersal: often easy to read Box Elder – Acer negundo CA poppy     Size/weight Flight/hitchhiking appendages Inside a fleshy fruit Characteristics of pod/capsule Jojoba - Simmondsia chinensis © Project SOUND
  50. 50. Others are a little more difficult  Pea family   Large, heavy seeds Characteristic pod  Plant distribution in landscape  Yellow Paloverde – Parkinsonia microphylla  Along seasonal streams Seeds distributed by water  Effective for dispersing large, heavy seeds over wide area  Ensures that seeds will be dispersed at a time conducive to germination  Ensures that plants grow where best suited to survive © Project SOUND
  51. 51. Seed distribution implications for gardeners  Some seeds are born to naturalize: small seeds [annual wildflowers]; windborn seeds [Milkweeds]  Plant species with fleshy fruits and you’ll attract fruit-eating birds & other dispersal agents  Remember, some seeds are meant to be carried in animal fur (clothing, etc.) [some grasses; cocklebur] sheet.cfm?ID=491 Yellow Paloverde Parkinsonia microphylla  Plants with unusual dispersal mechanisms may require special treatments to encourage them to germinate © Project SOUND
  52. 52. A seed is somewhat like a ‘manned’ space capsule der=%2Felmwood%2Flhippert%2FPicture%20Library74%2F1 90&products_id=404  A ‘capsule’ with a protective covering  Containing  A living organism: so dry that it’s in a state of suspended animation  Provisions for the journey & for re-settlement  Traveling through space & time © Project SOUND
  53. 53. The consequences of seed travel through time and space  Must have adequate protection – for wide range of possible conditions  Must have adequate provisions  Must provide everything needed to keep the ‘living being’ alive until it reaches it’s final destination  Must keep the weight/size down (usually – depends on dispersal)  Must not open the hatch-door until it’s reached its destination and conditions are ‘favorable’ © Project SOUND
  54. 54. The mighty seed monocot seed (corn)    Seed coat (testa) – protective coat Cotyledon/Endosperm - food source Embryo  Radicle (embryonic root)  Hypocotyl/epicotyl (embryonic root/shoot)  Plumule (embryonic shoot/leaves) © Project SOUND
  55. 55. Overview of Embryonic Development
  56. 56. A completely mature, dry seed remains in a state of suspended animation… sometimes for a very long time © Project SOUND
  57. 57. Seed germination: complex process Koning, Ross E. 1994. Seeds and Seed Germination. Plant Physiology Information Website.  What we’re interested in today is how does a seed begin the germination process – and what does it need to survive as a seedling © Project SOUND
  58. 58. You may have noticed that fresh seeds often germinate more easily …but most seeds don’t germinate prematurely. Why? © Project SOUND
  59. 59. The timing of germination is critical  Must be adequate resources for the seedling to survive: Immediate future     Water Light Nutrients Possibly other  Must not have future conditions that will kill a young seedling (seedling stage is the most vulnerable life stage): Slightly longer range California poppy - Eschscholzia californica  Too low or too high temperatures  Drought  Fire © Project SOUND
  60. 60. Plants have developed several strategies to prevent premature germination  Seed quiescence : delay germination because the external environmental conditions are not right : too dry or warm or cold for germination [most annuals; many fresh woody plant/perennial seeds]  Seed dormancy : seed is unable to germinate in a specified period of time under environmental conditions that are normally suitable for the germination of the non-dormant seed [many woody plant species normally facing challenging conditions] © Project SOUND
  61. 61. Several different processes: separate but often interrelated  Seed germination:  Depends on both external (environment) and internal (embryonic) conditions [seed maturity]  Environmental: water, oxygen, + temperature, light  Seed quiescence:  Depends on factors in the seed itself – ‘suspended animation’  Released when proper conditions for germination are present  Seed dormancy:  Depends on factors within the seed itself (but may require environmental cues that promote it)  Released by exposure to proper environmental conditions (the ‘triggers’) which ‘break’ dormancy and allow germination  Germination will not occur unless dormancy is broken © Project SOUND
  62. 62. Quiescence: a temporary hold on germination  Often due to seed dehydration ZZZzzzzzz  Seeds in state of ‘suspended animation’ ; ready to germinate once environmental conditions change for the better     The seed reaches soil The first rain The temperature warms up Etc.  The risks associated with quiescence strategy: premature germination if conditions again change for the worse [hot, dry conditions after the first rain] © Project SOUND
  63. 63. Dormancy: longer term strategy  Is a characteristic of the seed itself (not the environment); some seeds [those from tropical regions; typical garden plant seeds] exhibit no dormancy  Some CA native seeds are dormant when they leave the plant (primary dormancy) – insures dispersion will occur prior to germination  Others only become dormant only when they experience unfavorable conditions (too dry; too hot or cold) – secondary dormancy  Difference between fresh seeds and ‘older’ seeds is usually explained by secondary dormancy  Dormant seeds will not germinate unless dormancy is ‘broken’ © Project SOUND
  64. 64. Germination and dormancy are two different processes © Project SOUND
  65. 65. The life cycle of seeds: mediterranean climates © Project SOUND
  66. 66. Why is seed dormancy important?  Ensures time for seed dispersal  Prevents germination during unsuitable ecological conditions  Enables seeds to survive short periods of favorable conditions; when germination stimulating factors are present, but prevailing conditions are not suitable for subsequent seedling growth and plant development.  Prevents germination of all the seeds at the same time. The staggering of germination safeguards some seeds and seedlings from suffering damage or death from short periods of bad weather, transient herbivores, etc In other words, the dormancy evolved as a mechanism to postpone germination until a time and place that not only supports germination, but also maximizes seedling establishment and growth. © Project SOUND
  67. 67. Seed dormancy: many variations  Seed coat-imposed dormancy [AKA Exogenous/External dormancy] - caused by an impermeable seed coat  Embryo-imposed dormancy [AKA Physiological/endogenous/ internal dormancy] – caused by the embryo itself; prevents embryo growth and seed germination until chemical changes occur within the embryo  not due to any influence of the seed coat or other surrounding tissues  most abundant form of seed dormancy in angiosperm  thought to be due to the presence of inhibitors, especially ABA, as well as the absence of growth promoters, such as GA (gibberellic acid).  Combinations – why it’s sometimes hard to determine the factors needed to ‘break dormancy’ in a given species © Project SOUND
  68. 68. Seed coat-induced dormancy: several common mechanisms  Seed coat prevents water or oxygen uptake: [waxy coatings; special layers in seed coat that block water]  Hard seed coat prevents embryo from growing/emerging [coat must be softened/broken by exposure to stomach acids; mechanical means]  Seed coat contains growth inhibitors [must be leached away be repeated rinsing; exposure to chemicals that break down the inhibitors] © Project SOUND
  69. 69. Seed coat-induced dormancy: breeching the seed coat  Seed coat must be broken down to allow entry – embryos will germinate readily in the presence of water and oxygen once the seed coat and other surrounding tissues are either removed or damaged. m/articles/19-come-seminare-.html  Is usually all or none: once seed coat is breeched there’s no turning back – so timing is critical  Typically found in species from the families Fabaceae, Malvaceae, Chenopodiaceae, and Liliciae © Project SOUND
  70. 70. Scarification: breaking/fracturing seed coat to facilitate water/gas uptake  Mechanical : tumbling, abrasion, ‘nicking’, pounding etc.  Chemical : usually involves acid treatment like concentrated H2S04 (sulfuric acid), other acid treatments  Physical : hot water treatment; other heat treatment (burning)  Soaking/leaching : some seeds © Project SOUND
  71. 71. Treatments to break embryo-induced dormancy vary by plant  Common requirements/ treatments  Drying [after-ripening]  Low temperatures [stratification]  Alternating soaking/drying Hollyleaf redberry grows in dry places, often with colder winters – may require stratification  Applied by mother nature – or by the propagator  Clues from the native environment of the plant © Project SOUND
  72. 72. Chilling (stratification): exposure to coldmoist conditions  Prevents temperate climate seeds from germinating until the spring  Temperatures: 0-10° C (32-50° F)  Time: usually 1-3 months; seed supplier may specify Garden collected seed – may want to wash first in mild (5%) bleach solution to prevent fungal contamination  Seeds need to be fully hydrated – stratify in moistened vermiculite or moist paper towel/coffee filters in refrigerator  Need access to oxygen (air) © Project SOUND
  73. 73. Some environmental conditions that break embryo-induced dormancy in CA native plants           Drying [after-ripening - grasses] Low temperatures [stratification] High temperatures [heat stratification] Light (or dark) exposure Fluctuating temperatures (repeated heating and cooling over many months-years), Fire/smoke chemicals Freezing/thawing (may require cycles) Passage through the digestive tracts of animals/birds Removal/breakdown of fleshy fruit Acid treatment © Project SOUND
  74. 74. Important points about CA native seeds  They differ in the amount of stored food  Small amounts - must start producing quickly  Large amounts – live off stored ‘food’ for a while  They differ in the composition of their seed coat –some are harder than others  They germinate in response to cues (all seeds)     Water – cue + softens coat (all plants) Oxygen Light (small seeds) +Temperature  Some seeds are actually dormant until ‘awakened’ by environmental exposures © Project SOUND
  75. 75. Implications for gardeners: seeds  Storage:  Store seeds cool and dry  In general, smaller seeds have shorter ‘shelf-life’ than larger seeds  Planting: Once seeds have germinated, be sure to keep them adequately watered – very vulnerable to dehydration  Know if your seeds need pretreatment to break dormancy  Seed company instructions  On-line  Inference: place of origin; taxonomic  Plant seeds at the correct depth – some need light to break dormancy © Project SOUND
  76. 76. Be patient: just because you don’t see anything, doesn’t mean nothing is happening  Root development may occur before shoot development – particularly in large seeds [acorn]  Dormancy due to germination inhibitors may take some time  Cycles of hot and cool  Cycles of wet and dry  Many ‘washings’ to leach away or chemically modify the inhibitors © Project SOUND
  77. 77. How do plants grow? By adding modules  All plants are based on same basic pattern:  Shoot system  Main stem  Laterals (branches)  Root system  Primary root  Lateral roots Project SOUND ©
  78. 78. Shoot and root elongation and development is segmental in plants  Phytomere: developmental segment for shoot (shoot module) or root (root module)  Phytomeres develop from unspecialized cells in special areas of the plant – the apical meristems
  79. 79. Plant meristems: the plant’s ‘fountain of youth’  Apical meristems (shoot and root)  At the shoot and root tips  Give rise to the shoot or root modules  Result in elongation  Axial meristems  Located at/near a node  Give rise to branches  Lateral meristems  Located internally in shoots/branches  Responsible for growth in girth © Project SOUND
  80. 80. What do the meristems look like?  Central area with lots of simple cells  Surrounded by area of smaller cells (due to cell division)  Cells are more specialized looking (and larger) the further away from the meristem they are © Project SOUND
  81. 81. All cells, tissues & organs arise form cells in the apical meristems  Can traced origins back to the meristems  “Fate maps” can be drawn to trace the evolution of developing tissues  Apical meristem contains  Concentric rings of cells  Outer-most rings (segments) form lowest sets of leaves/stem segments  Pattern of development is somewhat like the water coming out of a fountain
  82. 82. Phyllotaxy – the arrangement of leaves on the stem  Is genetically determined – that’s why it’s often used in taxonomy & plant keys  Is determined by how much each new segment is offset around the stem © Project SOUND
  83. 83. Leaf arrangement/position (in relation to others) – phyllotaxy ©2009 Robert Steers © 2002 Kristiaan Stuart © Project SOUND
  84. 84. Why do plants grow (at least in part) by adding new segments?  Because that’s how they evolved  Efficiency: particularly in an everchanging environment  Redundancy/backup : plants need to be able to regenerate lost parts  As a consequence of a need for rigid structure © Project SOUND
  85. 85. Plant cells are a little different from our cells  One of the big differences is that they form cell walls  Primary cell wall  Formed first – just inside the cell (plasma) membrane  Strong but flexible  Allows for growth in certain directions (for example, cells can elongate)  Secondary cell wall  Formed inside the primary cell wall  Very strong; inflexible  No growth after secondary cell wall is formed © Project SOUND
  86. 86. What the heck! Why would plants do that?  Strong cell walls give plants the structure needed to grow tall  But plants still need to keep growing  Solution: add new segments on top of the old – requires apical © Project SOUND meristems
  87. 87. Consequences of sedentary life: scary!  Plants need to keep ‘rejuvenating’ themselves throughout life – roots and shoots  Therefore they continue to grow throughout their lives – sometimes for 1000+ years  In order to grow they need functional meristems [plant stem cells]  But what happens when something happens to an apical meristem (disease; herbivory)? Ancient (senescent) Bristlecone pine © Project SOUND
  88. 88. Fortunately, plants have a backup system  In most plants – most of the time – segments are added by the apical meristems  But there are ‘backup meristems’ – the axial meristems  Development of axial meristems is limited to a degree by the functional apical meristem – produces an inhibitory hormone  Once the apical meristem is gone, the axial meristems take over the job of elongation © Project SOUND
  89. 89. The shapes of plants'S/Plant%20Image s/Chicory.Rosette.jpg Stem elongation and control of the number of main shoots
  90. 90. The length of the internode is one determinant of plant shape  The main difference between the shape of a cabbage and a Southern honeysuckle vine is the length of the internodes © Project SOUND
  91. 91. The length of the internode: genetics and environment Southern honeysuckle - Lonicera subspicata ©2009 Robert Steers Turkish rugging - Chorizanthe stacticoides © Project SOUND
  92. 92. Take home messages  The basic structure (growth pattern/shape; mature size) is genetically determined. Choose plants accordingly  But…plants have enough flexibility programmed in to allow them to modify their shape based on conditions:  Limited water/nutrients – shorter internodes  Limited light – longer internodes as plant ‘reaches for the sun’ © Project SOUND
  93. 93. But internode length doesn’t explain all of the shape variability Torrey pine - Pinus torreyana Lemonadeberry – Rhus integrifolia © Project SOUND
  94. 94. Apical dominance: not all or none  Several plant hormones involved – degree of apical dominance depends on balance of these  Degree of apical dominance is genetically determined – that’s why a pine tree has a strong central leader and a shrub has many equal ‘stems’  You can (sometimes) make a strongly dominant form more shrub-like; it’s more difficult to go the other way around © Project SOUND
  95. 95. Tip-pruning (‘pinching’) removes apical dominance creating a ‘bushier’ plant  Just remove the tip – don’t need to take much  Must be done during periods of active growth  Must do repeatedly for best effects – new side branches will also exhibit apical dominance © Project SOUND
  96. 96. How far back can I safely tip prune/ prune to head back?  Lateral buds have an age – oldest at the base of a stem/trunk and youngest at the top  How long do lateral buds retain the ability to grow? Alas, no one answer.  But there are some rules of thumb:  Generally - but not always – lateral buds in older woody parts of stems have decreased/no growth potential  Generally – but not always – buds in semi-soft or soft wood (younger parts of stem) will grow © Project SOUND
  97. 97. Take home messages: pruning/shaping  When shaping woody plants, start when plants are young  Know taxa that require careful pruning:     Ceanothus spp Arctostaphylos spp Salvia spp Pinus spp  Prune ‘difficult’ species either:  During growth period (when wood is still semi-soft) for tip-pruning  When you can clearly apply the ‘leave 3-4 leafing buds’ rule © Project SOUND
  98. 98. What ‘materials’ do plants need from their environment?  Sunlight  Photons of light (energy for photosynthesis)  Air  Oxygen (to break down stored food)  Carbon dioxide (CO2) (for photosynthesis) ontent.htm How do these move around the plant?  Soil/medium  Water  Nutrients (minerals/ fertilizer) © Project SOUND
  99. 99. Roots (root hairs) are where water and minerals enter the plant  Good soils contain what plants need:  Water  Mineral nutrients (dissolved in the soil water)  Oxygen (needed by the roots so that they can obtain energy & perform their functions) © Project SOUND
  100. 100. The importance of soil water/oxygen balance  Too much water  Root oxygen depleted – decreased uptake of water, minerals  Too little water  Roots cannot uptake water or dissolved minerals That’s why the symptoms or over- and under-watering are the same © Project SOUND
  101. 101. Root characteristics: especially important with CA native plants  Coastal sage scrub shrubs  Primarily fibrous roots  Primarily shallow roots (< 3 ft)  Root:shoot ratio increases with water & nutrient stress  Chaparral shrubs ntwater.html Individual species have characteristic root growth patterns  Combination of deep and shallower roots  Root growth in spring/ summer  Root:shoot ratio increases with water & nutrient stress © Project SOUND
  102. 102. Root characteristics of some common CA native shrubs © Project SOUND
  103. 103. Use root characteristics to choose the proper plant – and treat it well!  Taproot  Likely very drought-tolerant  Plant is out young – don’t move  Not for containers  Fibrous roots  Look for depth characteristics  Shallow  may need occasional or regular water  Take care when digging  Good for containers  Good choice for slopes, banks  Lignotuber of_rooted_plant_material  Fire-adapted; may require occasional rejuvenation © Project SOUND
  104. 104. We’ll discuss roots more next month © Project SOUND
  105. 105. Development of the vascular system  New segments of vascular system are added by apical meristems  New layers of vascular tissue in older segments are added by lateral meristems (called vascular cambium)
  106. 106. Location of vascular tissues  Benefits  Two systems in close physical proximity – key to water/nutrient movement  Easy access for loading & unloading throughout the plant  New tissue can be added – even in woody parts  Somewhat protected (fiber cap; bark)  Drawbacks  Vulnerable location © Project SOUND
  107. 107. Take-home messages: plant vascular system  Soil water status is important not only for plant water needs, but also for mineral nutrition – more next month  Plant vascular tissues move all sorts of vital things around the plant body – an intact system is a must  Vascular tissues are vulnerable:  Girdling  ‘sucking’ insects [aphids]  Transport of toxins © Project SOUND
  108. 108. We hope you look at plants differently © Project SOUND
  109. 109.  Read a botany book  Use on-line resources – and refer others to them  Come back next month when we consider the effects of climate change © Project SOUND