1
Water Source Rain -> from evaporation -> water sources open to atmosphere (oceans, lakes, stream, etc.) Absorption is from soil moisture -> mostly from precipitation, some ground-water Basics of natural water cycling Evaporation -> deposition -> infiltration -> ground flow, storage, or uptake plants/animals Importance of water Up to 90% of growth can be attributed to available soil moistures Wood production correlates to water uptake Essential constituent of protoplasm Solvent for gases, salt (minerals & CO2) Reagent in photosynthesis Control turgidity -> cell enlargement -> stomatal opening 2
Sapwood Carries moisture and minerals Contains xylem and phloem Heartwood Tannins, resins, tyloses Structure & support 3
4
Closely related process by which water moves from -> soil -> root -> plant -> air Controlled by Flow 5
Water potential is negative -> except in fully turgid cells where it is 0 6
Water potential is controlled by varied gradients through-out the plant, depending on the stressor in the system Soil moisture Air temperature Wind Air humidity 7
Water moves differently in the soils depending on the texture of the soils Image is a vast over simplification, but a reasonable demonstration of how water moves through soils with different textures. Soil Temperature Poorly drained are slow to warm in the spring > effects grow Root hydraulic resistance increases in cold soil This dominates whole plant resistance as water is obtained (nearly) entirely from the roots Increases in air temperature increase vapor pressure gradient in tree -> increase transpiration -> Coupled with cold soil, may result in desiccation of foliage Soil warm slower than air (and cold slower than air) Cold soil Reduce water uptake Directly -> decreases the permeability of roots to water Indirectly -> through increased water viscosity 8
Water Absorption Depends on soil aeration Soil temp Soil concentration/composite of soil solutes Rate of water absorption Determined by the gradient steepness of water potential form soil -> roots Function of the resistance to water flow Increases as the soil dries Translocation of water Roots may lose water to dry soils Move water both vertically & horizontally (hydraulic redistribution) 9
Theory Water has high internal cohesion forces, can sustain tension into wettable walls of xylem (3-30 Mpa) Water forms a continuous network Water-saturated cells from leaves -> to roots Water potential change at evaporating surface forces water movement through xylem Cohesive attraction between molecules produces the needed tension Capillary Adhesion/cohesion Only a small distance 10.3 meters ~ 33.8 feet 10
Water potential Atmosphere < leaf < stem < roots < soil 11
Stomata Open in response to light & low CO2 concentration in intercellular spaces Closes in response to dehydrated leaves As abscisic acid (ABA) increases ABA synthesized in mesophyll as turgor approaches zero More ABA moves from roots to leaves through xylem Important regulator of stomatal opening Cytokinins promote opening Negative signal - > reduces translocation ABA Positive signal translocated roots - > leaves => closure (more water stress => more ABA) Produced in dehydrated roots 12
Resistance to water flow in leaf Epidermis & cuticle Differs by species More wax = better adaptation to drought Waxes can occlude stomatal openings Which can significantly reduce transpiration Resistance to diffusion of water vapor differs by species Open stomata have lower resistance to diffusion than cuticle Principal factor is the stomatal aperture Wind High wind reduces air resistance, low wind increases diffusion resistance of air 13
Wind Thins boundary layer of water vapor reducing resistance Increasing transpiration Also acts to decrease transpiration by cooling leaves Soil moisture Less water -> less transpiration (stomatal closure) Soil field capacity Atmospheric factors are the controlling force Exception in midday where transpirational rate exceed adsorption rate due to increased root resistance Reduce transpirational likely a combination of factors of leaf water deficits & chemical signaling form root (ABA) 14
Spiral Trachied & border pit arrangement can allow water to move horizontal & vertical Lots of variability may account for damage on one side of vascular system impacting the opposite side of the tree Most effective/redundant Faster disease movement in red oak vs white oak 15
Flooded soil, past field capacity Flooding induces stomatal closure -> drought like response in trees Increases resistance of water flow to roots -> drought like response in trees Adventitious root development (if flooded soils persist) Tree adaptations Low soil oxygen -> formation of aeranchyma tissues in roots & stems (in water/low oxygen) Aeranchyma -> larger intercellular spaces Formed by shiogeny (cell separation) & lysigeny (disintergration, programmed cell death) Mediated by ethylene accumulation -> production of ethylene stimulated by auxin increases Some species are capable of internal aeration 16
Anti-transpirants Some survival increases in seedlings Issues Dependent on species, developmental stage, & atmospheric conditions Did not reduce winter injury New foliage needs reapplication / some chemicals may effect environment negatively Reduction in photosynthesis & CO2 uptake (ultimately a growth reducer) ABA (natural anti-transpirant) Causes stomatal closure Species dependent (but non-toxic) Can enhance growth: Plant Physiol. (1972) 49, 722-724 Some Counteractive Effects of Antitranspirants1 Received for publication September 30, 1971 D. C. DAVENPORT, M. A. FISHER, AND R. M. HAGAN Department of Water Science and Engineering, University of California, Davis, California 95616 17
18
Pith is not always at the geometric center of the tree Differences in growth response to the environment can cause the pith to be offcenter. Xylem living sapwood, inside cambium layers Outer xylem stores & conducts and storing starch in the symplast Conducts water & minerals to leaves Inner portion of the xylem - non-conducting wood - stores starch (heartwood) Vessels elements in angiosperms (hardwoods) Tracheids in gymnosperms (conifers) Phloem (inner bark) Outside layer of the cambium Transports sugars - leaves -> roots Storage sugar = starch, can be converted to sugars & transported Sieve tubes (living nucleus at maturity) 19
The process of photosynthesis is very complex but at the heart it is the reduction of atmospheric carbon dioxide into carbohydrates that trees use as food/energy/growth Chemical formula 6CO 2 + 12H 2 O -> C 6 H 12 O 6 + 6O 2 + 6H 2 O Simplified: carbon dioxide + water --converted with light energy into--> glucose (carbohydrates, sugars) and oxygen and water You need: Light, generally sunlight, however any light in the red or blue wavelengths will provide the appropriate energy The correct photoperiod, basically there must be enough light in the proper wavelengths to maintain growth Water must be available or no photosynthesis can take place Temperature must be in the correct range, too hot or too cold and photosynthesis is minimized or does not take place Essential nutrients Specifically magnesium (Mg), manganese (Mn), and nitrogen (N) Must be available for plant uptake 20
Thinking about light disrupting growth Chlorophyll a blue light in 450nm &red light 645nm green pigment Chlorophyll b blue light in 475nm & red light 660nm yellow pigment Light absorption in between red and blue spectrum (the green spectrum) 21
Leaves are the main photosynthetic organs of deciduous trees They contain: Cells Chloroplasts are a structure in the leaf cells where the majority of photosynthesis takes place Exposure to light activates chlorophyll Primarily a&b with some accessory pigments Chlorophyll a blue light in 450nm &red light 645nm green pigment Chlorophyll b blue light in 475nm & red light 660nm yellow pigment Light absorption in between red and blue spectrum (the green spectrum) Accessory pigments Carotene - an orange pigment Xanthophyll - a yellow pigment Phaeophytin a - a gray-brown pigment Phaeophytin b - a yellow-brown pigment Stomata Structures on the underside of the leaf which open and close Water is moved along a gradient which controls movement of water from roots to leaves Closed = little water movement, which means reduced photosynthesis Open = water movement, which means active photosynthesis Nutrients, Mg is the center of the chlorophyll molecule 22
23
Plant metabolism: energy stored as carbohydrates in stems and roots is used to Maintain energy input and output throughout entire tree Produce of fine roots and leaves Produce flowers and seeds Elongate roots and stems/branches Lateral growth and addition of wood to stem, roots and branches Create defense chemicals Chemical formula C 6 H 12 O 6 + 6O 2 -> 6CO 2 + 12H 2 O Simplified: glucose (carbohydrates, sugars) and oxygen --converted with energy from ATP and ADP into--> carbon dioxide + water + Energy Annual Energy Curve January: some energy reserves used in respiration February: some energy reserves used in respiration March: increasing temps, starts sugar flow to buds April: Continued increasing temps, increases sugar flows to buds May: stored sugar movement to tree buds and tissues increases as deacclimation process completes, root activity begins June: most stored sugar has been depleted, as new leaves are developed July: replenishing some sugar stored in roots and stems, tree is fully photosynthesizing and growing August: Approaching maximum sugar stored in roots and stems, growth continues, but slows September: maximum sugar stored in roots and stems (assuming good growing season) growth is slowing October: maximum storage reached and depletion starts as tree begins acclimation process November: some energy reserves used in respiration December: some energy reserves used in respiration If respiration rates exceed rates of photosynthesis Carbohydrate reserves will become depleted Trees become stressed Stressed trees are more susceptible to disease/pests Over a long period (more than 5 yrs) Tree decline and eventual death 24
25
In spring Sugars from roots and stem storage flow to bud Buds begin to swell and leaves unfurl Energy reserves are depleted once leaves are on the tree Photosynthesis can resume Limiting factors Water, nutrients and sunlight Too much or too little will cause growth to slow or stop 26
Height growth The development of the apical (above ground) meristems Elongation of branches/trunks/main stem Height is controlled primarily through genetics Although environmental factors can play a role (stunted root system may dwarf a tree) Lateral growth The thickening of branches, trunks, and roots Starts once the tree is actively photosynthesizing Annual rings develop Ring porous trees (oak, ash) have distinct spring and summer wood Spring wood is lighter in color Summer wood is darker in color Diffuse porous trees (maple, basswood) have less distinct spring and summer wood Annual rings are more difficult to distinguish Root growth Root growth resumes once the soil is warm enough There may be minimal root activity year long Roots grow both horizontally and vertically Typically growing toward an appropriate mixture of water and oxygen 27
Self-sustaining The cambium is a self-sustaining system, and retains its functions for a long time (sometimes for centuries or millennia). Resource-intensive As the cambium grows, it consumes scarce resources that cannot be used for growth by the rest of the tree. Flexible Cells produced by the cambium (called cambial derivatives) can be differentiated into the range of cells found in the xylem and phloem. 28
Growth happens at the meristems via cell division, enlargement, and elongation One cell becomes two cells, they get larger and divide 29
Water storage: Sapwood stores most of the water Gymnosperms > angiosperms Diffuse porous > ring-porous Seasonal depletion of water greatest in conifers -> diffuse -> ring porous 30
31
Image = eastern white pine Tracheids dead, single-celled "pipes" that act much like vessels Resin canals typically a response to injury elongated cells that function in water conduction and structural support. most common type of cell in conifers. Much less frequent in deciduous trees. Parenchymal rays carries waste, water, carbohydrates laterally through the tree. Crosses the annual ring boundaries, existing in nearly all species. 32
Image = american elm Vessels (in hardwoods) conduct water and substances dissolved in water Vessels - vertically aligned tubes made up of dead cells that transport liquid a type of hardwood cell that has a relatively large diameter, thick cell wall and perforate (open) ends. combines to form vessels, long passageways used to conduct water and soluble nutrients. 33
Parenchymal Rays flattened bands of tissue that extend horizontally in a radial plane through the tree stem. transport sap and wastes produced by photosynthesis. 34
Diffuse porous trees (maple, basswood) have less distinct spring and summer wood Annual rings are more difficult to distinguish Slower water and nutrient transportation 35
Image Black oak Ring porous trees (oak, ash) have distinct spring and summer wood Spring wood is lighter in color Summer wood is darker in color Fast water/nutrient transport Lots of in-betweens Semi-diffuse, semi-ring 36
heartwood created as a result of the programmed death of parenchymal rays that are filled with extractives (tannins, resins, oils, etc) some heartwood is the same color as sapwood, where others different in color. in "a few species" heartwood may not ever form, example give is a tropical tree Alstonia scholaris. Sapwood Conducts water & nutrients Usually only one or a few years conduct 37
Reaction wood redistribution & nature of cambial growth Response to some environmental stimuli Tendency to shrink, warp, weakness 38
Pith is the growth center.not always the geometric center 39
Healthy trees can seal off the affected area and grow new tissue around the damage, but the damage has been done. That s why you can see things like old knots in wood that are usually a different color than the surrounding wood. The branch was removed while the tree was still living and the tree grows over the wound. Some tree species compartmentalize better than others. Diffuse porous species (maples, basswoods) move pathogens slower than ring porous Knowing once a tree is wounded it is wounded for life gives a great incentive to protect trees. If a small branch is wounded it can easily be removed without too much stress on the tree However if the trunk is wounded it s difficult to remove the trunk without drastically affecting the growth and appearance of your tree. Young trees, like kids, can be hurt more easily, but they can also recover well if they are kept healthy. Poor compartmentalization of wounds can lead to serious tree decay and hazardous situations 40
Contrary to common perception trees don t heal they compartmentalize they form cellular walls all around a wounded area in order to protect the rest of the tree from decay or outside harm. The part of tree that has been wounded stays that way for the remainder of the tree s life. Compartmentalization Compartmentalization Of Decay (Damage, Disease) In Trees (CODIT) 41
42
43
44
45