How does a Tree grow?  (feat fungal friends)

How the first trees grew:  This video demonstrates how scale trees figured out how to grow tall - they had to rip themselves apart!!! 

Key Distinctions from Modern Trees:

• Complex Vascular Networks: Unlike the single cylindrical trunk of most modern trees, ancient trees like the 374-million-year-old Cladoxylopsida possessed a web-like vascular system composed of interconnected woody strands surrounding a hollow pith in the center. This likely facilitated efficient water and nutrient transport, enabling them to reach substantial heights despite their primitive nature.

• Self-Destructive Growth (or "Pith Decay"): The hollow pith at the center of these ancient trees played a crucial role in their growth. As the tree grew wider, the pith would tear itself apart, creating space for the woody strands to expand and thicken. This self-destructive process allowed the tree to increase in girth without the need for a continuous, solid trunk.

• Modular Growth: Unlike modern trees with a single apical meristem responsible for upward growth, ancient trees likely exhibited modular growth with multiple growing points. This resulted in a wider, more stable base, potentially offering greater resilience against environmental stressors like strong winds or unstable substrates.

• Adaptation to Ancient Environments: These trees evolved in vastly different conditions than today's trees, with varying atmospheric composition and environmental pressures. Their unique anatomical features, such as the interconnected woody strands, hollow pith, and modular growth, likely arose as adaptations to these specific challenges.

• Compartmentalization of Decay: Ancient trees have developed sophisticated mechanisms to isolate and compartmentalize areas of decay or damage, preventing the spread of pathogens and significantly extending their lifespan. This is in contrast to modern trees, which exhibit less compartmentalization and often have shorter lifespans.

Tree Domination: A Story of Adaptation and Evolution

• Early Plants:

  • Started as small, moss-like organisms in the Devonian period.

  • Faced challenges of dry land, needing to stay hydrated.

• Vascular Tissue and Wood:

  • Xylem emerged to transport water from roots to top.

  • Secondary xylem (wood) provided strength and support, made of cellulose and lignin.

  • Wood initially helped with water retention, later evolved for height and competition.

• Reproduction:

  • Early reproduction relied on spores, requiring wet environments.

  • Archaeopteris developed male and female spores, larger female spores with food supply for embryo, a precursor to seeds.

• Rise of Archaeopteris:

  • One of the earliest modern trees, reaching up to 30 meters tall.

  • Deep root system for better water and nutrient collection.

  • Roots created new habitats and enriched soil through breakdown and wood decay.

• Impact on the Environment:

  • Trees changed the atmosphere and land, creating conditions for other life forms.

  • By the end of the Devonian, plants had the key adaptations: roots, wood, leaves, and seeds.

• Conclusion:

  • Trees played a crucial role in transforming the Earth, paving the way for the world we know today.

  • Their evolution highlights the importance of adaptation for survival and success in a changing environment.

Key Terms:

• Devonian period

• Xylem

• Secondary xylem (wood)

• Cellulose

• Lignin

• Archaeopteris

• Spores

• Seeds

This video presents a comprehensive analysis of global tree populations, utilizing data from a recent study published in Nature. The study employed a combination of satellite imagery, ground-based surveys, and statistical modeling to estimate the total number of trees worldwide at approximately 3.04 trillion.

Key Findings:

• Distribution: The study reveals that almost half of the world's trees are concentrated in tropical and subtropical regions, while boreal forests account for a significant portion.

• Density: Tree density varies significantly across different biomes, with the highest concentrations found in boreal forests and the lowest in arid regions.

• Loss and Gain: The study estimates that the world is losing approximately 10 billion trees annually, primarily due to deforestation and land-use change. However, there is also evidence of new growth and reforestation efforts in some regions.

• Human Impact: The video highlights the significant impact of human activities on global tree populations, both through direct deforestation and indirect effects like climate change and pollution.

Implications for Research and Conservation:

• Biodiversity Conservation: The data on tree distribution and density can inform conservation efforts by identifying priority areas for protection and restoration.

• Climate Change Mitigation: Trees play a crucial role in carbon sequestration, and understanding their distribution and abundance is essential for modeling climate change scenarios and developing mitigation strategies.

• Ecosystem Services: Trees provide a wide range of ecosystem services, such as water purification, soil stabilization, and habitat provision. This research can help quantify the value of these services and inform land management decisions.

• Future Research: The video highlights the need for ongoing monitoring of tree populations to track changes over time and assess the effectiveness of conservation efforts.

Conclusion:

This research represents a significant step forward in our understanding of global tree populations. It provides valuable data for scientists, policymakers, and conservationists to develop effective strategies for managing and protecting these vital ecosystems. However, the video also underscores the urgency of addressing the ongoing loss of trees and the need for concerted global action to mitigate the impacts of human activities on forest ecosystems.

This video provides some basic terms when looking at wood.  It is a great practical first look!

• layers of tree - outer bark, inner bark, cambium (living part responsible for growth), sapwood (active vascular transport), pith (original embryo tissue for initial growth), heartwood (dead internal)

• Tree rings - early wood/late wood delineated by differences in vascular structures, medullary rays (parenchyma cells that enhance strength)

SUMMARY

This comprehensive examination of tree anatomy and growth processes utilizes a cross-section of a white oak log as a visual aid. It provides a detailed exploration of the diverse tissues within the tree and their intricate roles in overall tree function and development.

Outer Structure and Protection:

• Bark:

  • Periderm: The outermost layer, consisting of cork cells (phellem), cork cambium (phellogen), and phelloderm. The cork cells are dead at maturity, providing a protective barrier against pathogens, desiccation, and physical damage. The cork cambium produces new cork cells to replace those that are sloughed off. The phelloderm is a layer of living parenchyma cells that contributes to the tree's ability to repair wounds.

  • Cortex: Lies beneath the periderm and is composed of parenchyma cells, which store starch and other nutrients.

  • Inner Bark (Phloem): Transports photosynthates (sugars) from leaves to other parts of the tree, including roots, stems, and developing fruits. The phloem is composed of sieve tube elements (conducting cells), companion cells (provide metabolic support to sieve tube elements), and phloem parenchyma cells (storage and lateral transport).

Growth and Transport:

• Cambium: A thin layer of meristematic cells located between the xylem and phloem. It is responsible for secondary growth, producing new xylem cells towards the inside and new phloem cells towards the outside. This lateral growth increases the tree's girth.

• Xylem (Wood):

  • Earlywood (Springwood): Formed during the spring when water is abundant, characterized by larger, thin-walled cells that allow for efficient water transport.

  • Latewood (Summerwood): Formed during the summer when water is less available, characterized by smaller, thick-walled cells that provide structural support.

  • Heartwood: Older, non-functional xylem that often darkens due to the accumulation of resins and other compounds. It provides structural support but does not transport water.

  • Sapwood: Outer layers of xylem that actively transport water and nutrients.

• Medullary Rays:

  • Radiating lines of parenchyma cells that extend from the pith to the bark.

  • Responsible for the radial transport of water, nutrients, and storage compounds between xylem and phloem.

  • Add a web of strength to the wood

Central Core:

• Pith: The central core of the tree stem, composed of parenchyma cells. In young stems, it may function in storage, but in older stems, it often disintegrates and becomes hollow.

Additional Considerations:

• Growth Rings: Annual layers of xylem tissue that form as a result of seasonal variations in growth rates. These rings provide valuable information for dendrochronology (tree-ring dating) and understanding past climatic conditions.

• Tyloses: Outgrowths of parenchyma cells into xylem vessels, common in heartwood. They help to block the vessels, reducing the risk of decay and pathogen spread.

• Reaction Wood: Specialized xylem tissue formed in response to mechanical stress, such as leaning or bending. It helps to reorient the tree and maintain structural integrity.

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Understanding tree anatomy and growth processes is crucial for various fields, including forestry, ecology, and climate science. The knowledge gained from studying trees like the red oak can be applied to sustainable forest management, conservation efforts, and understanding the impacts of climate change on forest ecosystems.

Watch this video for an introduction into how trees grow (secondary growth) with the added wrinkle of "pulsating" growth

• Take a look at the animation of how trees grow from the cambium

• Trees swell and shrink with daily update and transpiration of water - heat and cloud cover modulate this relationship

This educational video by the U.S. Forest Service provides a simplified yet comprehensive overview of tree growth and development, suitable for introductory botany or forestry courses. It employs time-lapse footage and animations to illustrate the dynamic processes occurring within trees, emphasizing their continuous growth and change throughout the seasons.

Key Points:

1. Seasonal Growth Patterns: The video highlights the cyclical nature of tree growth, with periods of rapid expansion in spring and summer followed by slower growth or dormancy in fall and winter. This seasonal pattern is reflected in the formation of annual rings within the tree's trunk.

2. Cambium: The video emphasizes the role of the cambium, a thin layer of cells beneath the bark, as the engine of tree growth. The cambium produces new xylem cells (wood) towards the inside and new phloem cells (inner bark) towards the outside, increasing the tree's girth.

3. Xylem and Phloem: The video explains the functions of these two vascular tissues. Xylem transports water and nutrients from the roots to the leaves, while phloem carries sugars produced in the leaves to other parts of the tree for growth and storage.

4. Buds and Branches: The video demonstrates how buds, located at the tips of branches and along the trunk, contain the embryonic tissues for new leaves, flowers, and stems. These buds burst open in spring, fueled by stored energy and nutrients, leading to the expansion of foliage and the development of new shoots.

5. Environmental Factors: The video touches upon the influence of environmental factors on tree growth, including sunlight, water availability, temperature, and nutrient levels. These factors play a crucial role in determining the rate and pattern of tree growth.

Detailed video showing primary and secondary growth

• primary growth - primary meristem - lengthening of stems and roots

• secondary growth - increase in girth of stem and roots

• secondary meristems = vascular cambium and cork cambium

  • • Wood is produced by vascular cambium (intrafascicular cambium) - found in a vascular bundle between primary xylem and primary phloem - is patchy when stem is young but forms the uninterrupted cambrial ring as developed

      • • medullary ray cells next to intrafasicular cambium become meristematic and produce interfascicular cambium to complete the ring

      • Once cambrial ring is formed - primary xylem is on its inner surface and primary phloem is on its outer surface - cell division happens on both sides of cambrial ring - secondary xylem and phloem are formed on inner and outer surface respectively...this is essential how a tree grows!

      • The cambial ring is more active on the inside than the outside...as the tree grows the phloem on the outside of the cambrial ring gets crushed while the xylem on the inside does not - eventually resulting in the formation of wood inside the cambrial ring

      • Secondary medullary rays are formed by parenchyma produced by cambrial ring

      • Wood formation (and tree rings affected by:  defoliation, light, diseases, drought, temperature) - rings formed because some conditions/seasons result in active cambial division (spring) while others (winter) do not in temperate regions

      • tanins, resins, gums, and essential oils are deposited in wood to discourage insect attack

  • Bark is produced partially by cork cambium (phellogen) - cell growth on both sides - inner = secondary cortex (phelloderm), outer = cork (phellem) -- all together these three layers are called the periderm

  • Secondary phloem and periderm together make up the bark

  • Lenticels - openings in bark to allow gas exchange between tree stem and atmosphere

  • Secondary growth also occurs in roots by a similar process

  • monocots do not have secondary growth - palm trees, corn, grasses, etc.

SUMMARY:

Secondary Growth in Dicotyledonous Plants: A Detailed Explanation

Secondary growth is the process by which plants increase their girth or thickness, primarily in stems and roots. It is characteristic of woody dicots and gymnosperms. This detailed explanation elucidates the mechanism of secondary growth:

1. Formation of Vascular Cambium:

• Origin: The vascular cambium originates from two sources:

  • Intrafascicular Cambium: A primary meristem located between the primary xylem and phloem within vascular bundles.

  • Interfascicular Cambium: A secondary meristem that develops from parenchyma cells between the vascular bundles.

• Cambium Ring: The intrafascicular and interfascicular cambia join to form a continuous ring of meristematic cells called the vascular cambium.

2. Activity of the Cambium Ring:

• Cell Division: The vascular cambium cells undergo active cell division, producing two types of daughter cells:

  • Fusiform Initials: Elongated cells that differentiate into secondary xylem (wood) towards the inside and secondary phloem (bast) towards the outside.

  • Ray Initials: Isodiametric cells that form radial files of parenchyma cells called medullary rays.

• Secondary Xylem Formation: Fusiform initials divide and differentiate into various xylem elements: tracheids, vessels, fibers, and xylem parenchyma. These cells are lignified, providing structural support and conducting water and minerals.

• Secondary Phloem Formation: Fusiform initials also give rise to sieve tube elements, companion cells, phloem fibers, and phloem parenchyma. These cells are involved in the transport of organic nutrients.

3. Formation of Annual Rings:

• Seasonal Activity: The vascular cambium is most active during spring and early summer (springwood or earlywood), producing large, thin-walled xylem cells. In late summer and autumn (autumn wood or latewood), it produces smaller, thick-walled cells.

• Distinct Rings: This variation in cell size and wall thickness creates distinct annual rings visible in a cross-section of the stem.

4. Heartwood and Sapwood:

• Heartwood Formation: As the stem ages, the inner layers of xylem become non-functional due to the accumulation of resins, tannins, and other compounds. These darker, central layers constitute the heartwood, providing structural support.

• Sapwood Function: The outer, lighter layers of xylem remain functional and are called sapwood. They are responsible for the conduction of water and minerals.

5. Cork Cambium and Bark Formation:

• Origin: In woody plants, the cork cambium (phellogen) arises in the outer cortex or epidermis.

• Periderm Formation: The cork cambium produces cork (phellem) towards the outside and phelloderm towards the inside. This three-layered structure (cork, cork cambium, and phelloderm) is called the periderm and replaces the epidermis as the protective outer layer.

• Bark: The bark includes all tissues external to the vascular cambium, encompassing the periderm and any remaining cortex and phloem.

Dendrochronology - cross-dating trees and using tree rings to generate paleoclimate data

• used as a climate record from before the instrumental record

• information directly useful to managers to forecast drought, flood, etc.

The video "Tree Stories: How Tree Rings Reveal Extreme Weather Cycles" explores how scientists use dendrochronology, the study of tree rings, to understand past climate patterns and extreme weather events.

Key points:

• Tree rings as a climate record: Each tree ring represents a year of growth, and the width of the ring indicates the environmental conditions during that year. Wider rings typically represent favorable conditions like abundant rainfall, while narrower rings indicate droughts or other stressors.

• Dendrochronology: Researchers use dendrochronology to analyze tree ring patterns, comparing them across different trees and regions to reconstruct past climate events, including droughts, floods, and temperature fluctuations.

• Utah drought study: The video highlights a study conducted by Brigham Young University researchers who analyzed tree rings in Utah, revealing a previously unknown 16-year megadrought in the 1700s. This finding has implications for water management and drought preparedness in the region.

• Applications of dendrochronology: Beyond climate research, dendrochronology has applications in archaeology, forestry, and ecology. It can help date historical structures, track forest growth patterns, and understand the impact of climate change on ecosystems.

Overall, the video demonstrates how tree rings serve as a valuable natural archive of past climate conditions, providing crucial insights for understanding and preparing for future climate variability and extreme weather events.

A great video showing how trees are connected through fungi

• Trees share food, supplies, and wisdom

• Mycorrhizae - symbiotic fungi partnering with plant roots - fungal hyphae form mycellium to extend root network

• Mycorhizal networks - pass nutrients and signaling molecules from tree to tree

• Oldest trees have the largest and most connected networks - they are very complex and hard to trace

• 100 species of mycorihizal fungi!

• Mycohirizal fungi either surround (ectomycorizae) or penetrate (endomycorhyizae) plant root cells - fungi can process organic matter (plants can't) so the fungi are able to more readily access nutrients and pass them to the tree root system

• plants provide sugars to fungus through root exudates of sugars

• sugars pass through hyphae, some are absorbed by fungus but others are passed through networks to other trees

• This symbiotic relationship between fungi and plant makes sense...both parties benefit...but......

• We don't completely understand why fungi would pass sugars to other trees but here are some ideas:

  • • fungus could benefit by having as many connections between trees as possible and gains the most connections by shuttling materials between trees

    • perhaps trees reduce interactions with fungi that don't facilitate connections between trees

• Trees can tell if info is coming from their own species, or even their own relatives within a population!

• Drought or insect attack info is also passed through the fungal network

More descriptions about this fungal network system

• Mother trees protect and nurture seedlings through wood wide network

• Sick and dying trees dump resources into the network before they die to help their neighbors

• If attacked plants send messages to neighbors to warn them to ready their defenses

• Orchids hack the system to steal resources from nearby trees

• Black walnuts send hazardous chemicals through network to poison rivals (allelopathy)

Very cool REAL video of fungal hyphae carrying nutrients around.

The video "The Secret Language of Trees" delves into the intricate world of communication and cooperation among trees, highlighting their symbiotic relationships with fungi and the formation of complex underground networks.

Mycorrhizal Networks:

• Symbiosis: Trees form mutually beneficial partnerships with mycorrhizal fungi. The fungi colonize the tree's roots, extending their hyphae (thread-like structures) into the soil.

• Nutrient Exchange: The fungi enhance the tree's ability to absorb water and nutrients, such as phosphorus and nitrogen, from the soil. In return, the tree provides the fungi with sugars produced through photosynthesis.

• Wood Wide Web: The interconnected network of tree roots and fungal hyphae forms a vast underground communication system, often referred to as the "wood wide web." This network facilitates the exchange of nutrients, water, and chemical signals between trees.

Chemical Signaling:

• Volatile Organic Compounds (VOCs): Trees release VOCs into the air and soil to communicate with each other. These signals can convey information about threats like insect infestations, droughts, or diseases.

• Defense Mechanisms: When a tree detects a threat, it can release VOCs that trigger defense responses in neighboring trees. For example, some trees increase the production of tannins, making their leaves less palatable to herbivores.

Resource Sharing:

• Mother Trees: The documentary highlights the role of "mother trees," older, larger trees that act as hubs in the mycorrhizal network. These trees share resources with younger, weaker trees, helping them to survive and thrive.

• Carbon Transfer: Research suggests that mother trees can transfer carbon through the mycorrhizal network to seedlings, aiding in their establishment and growth.

Forest Resilience:

• Collective Defense: The interconnectedness of trees through the wood wide web allows for a collective defense against threats. By sharing information about potential dangers, trees can respond more effectively and increase their chances of survival.

• Ecosystem Stability: The mycorrhizal network plays a crucial role in maintaining the stability of forest ecosystems. It helps to distribute resources, promote biodiversity, and enhance the resilience of forests to disturbances like fire or disease.

Conclusion:

The documentary reveals the remarkable ability of trees to communicate and cooperate, challenging the traditional view of them as solitary organisms. By understanding the intricate relationships between trees and fungi, we can gain valuable insights into the functioning of forest ecosystems and develop more sustainable forestry practices. This knowledge can also inspire new approaches to agriculture, conservation, and ecological restoration, ultimately leading to a healthier and more resilient planet.