Plant Nutrition

What is an essential nutrient?

• An organism can’t complete its life cycle in the absence of that element

  • element could be an element itself or could be part of a molecule

• The element is part of an essential molecule or constituent

Typical dose-response curve for an essential element

• x axis: conc of particular element in tissue

• y axis = response to having that element in the tissue

• if the element is require there will be some sort of critical conc needed to do essential functions, below which the response will be minimal or absent; this highlights the importance of maintaining adequate levels of the element for optimal physiological functioning.

• range of which that a conc is adequate can be very broad or very small and this can vary between different species

  • anything can be toxic in a high enough conc.

  • adequate range is when organism grows at its maximal potential

Dose-response curve for a non-essential element

• no critical conc bcs its not an essential component but it has a toxic range for when there is too much of this element

  • range of which this element can be tolerated is often referred to as the threshold level, beyond which adverse effects on the organism's growth and overall health may be observed.

Essential elements for plants

• Macronutrients

  • Nitrogen: Vital for growth and development, playing a key role in amino acids and proteins.

  • Phosphorus: Important for energy transfer and photosynthesis, crucial for root development.

  • Potassium: Essential for water regulation and enzyme activation, aiding overall plant health.

  • Carbon: Fundamental for photosynthesis and organic molecule formation, serving as the backbone for carbohydrates and other vital compounds.

  • Hydrogen: Vital for photosynthesis and respiration, playing a key role in energy production and maintaining plant structure.

  • some are require in high abundance and some are required in low abundance, but all are crucial for optimal plant growth and development.

  • Magnesium is needed for chlorophyll production, which is essential for photosynthesis, as it helps capture light energy and convert it into chemical energy.

  • Oxygen: Essential for respiration in plants, oxygen is produced as a byproduct of photosynthesis and is crucial for cellular respiration, enabling plants to convert glucose into energy.

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• Micronutrients

  • Micronutrients: Required in smaller quantities, they support various physiological functions and are essential for enzyme activity and chlorophyll production.

  • Calcium: Vital for cell wall structure and stability, it plays a key role in cell division and growth.

  • Magnesium: Important for photosynthesis, it serves as a central component of chlorophyll and helps in the activation of several key enzymes.

Elements essential for some plants

• CAM and C4 plants have a high demand for sodium partly because they live in dry environments, where sodium helps in maintaining osmotic balance and enhances their photosynthetic efficiency.

• cobalt is essential for nitrogénase used for N-fixing

Mobile nutrients

• mobile elements can move around throughout the plant (translocated) through the phloem, allowing for the distribution of nutrients like potassium, magnesium, and phosphorus, which are crucial for various physiological processes such as energy transfer and enzyme function.

• deficiency symptoms will occur first in old tissue because nutrients are being supplied to new tissue for growth, leading to stunted growth and yellowing of older leaves as the plant reallocates its resources.

Immobile nutrients

• immobile nutrients can’t be transported throughout the plant, meaning that deficiency symptoms will appear in younger tissues first, as the plant cannot redistribute these essential nutrients from older tissues.

• once they are in the tissue they are stuck there being used for whatever they are needed; therefore, any deficiency will manifest in the areas where these nutrients are most critical for immediate growth and development.

• sulfure and iron deficiency can lead to specific symptoms such as yellowing of young leaves and stunted growth, highlighting the importance of these nutrients in the early stages of plant development.

Nutrients in Soil

• plants obtain most of their nutrients from the soil by their roots, which absorb essential minerals and elements that are vital for various physiological processes. This uptake is influenced by several factors, including soil pH, moisture levels, and the presence of organic matter.

• there is both water outside of the plant and moisture within the soil that contribute to nutrient availability and uptake, ensuring that plants can thrive and grow effectively.

Nutrients reach roots via diffusion and bulk flow

• depletion zone: a region surrounding the root where nutrients are absorbed, leading to a localized reduction in nutrient concentration, which can impact the overall nutrient uptake efficiency. The efficiency of nutrient absorption in the depletion zone can be affected by factors such as root density and the presence of mycorrhizal fungi, which enhance nutrient mobilization and uptake.

• zero zero point says that there is no nutrients at the roots surface , indicating that nutrient concentrations are significantly lower in this immediate area compared to the surrounding soil, which can lead to competition for available nutrients and potentially limit plant growth.

• further out you go from the roots the more nutrients you find, as the concentration gradient favors the movement of nutrients towards the depletion zone. This phenomenon emphasizes the importance of root architecture and growth patterns in maximizing nutrient acquisition and overall plant health.

• movement of water down the water potential gradient also moves nutrients by bulk flow, facilitating the transport of essential elements from the soil into the root system. This process is critical for maintaining the plant's hydration and nutrient status, as it ensures that nutrients are readily available for uptake, particularly during periods of high demand, such as growth or flowering.

Not all nutrients are readily available

• most soil particles are negatively charged… this is a problembecause it causes essential positively charged nutrients, like calcium and magnesium, to be held tightly by the soil, making them less available for plant uptake. This highlights the need for effective nutrient management strategies to enhance soil fertility and support plant growth.

  • bcs they are negatively charged they attract positively charged ions and the ions bind to the soil , creating a complex interplay that can limit the availability of these essential nutrients. As a result, plants may struggle to access the required amounts of calcium, magnesium, and other vital elements necessary for optimal growth.

  • anions are repelled by the soil and thus remain more available for plant uptake, as they do not bind as tightly to the negatively charged soil particles.

Plants can alter nutrient availability

• pumping protons into the soil can impact nutrient availability by changing the pH and influencing the charge of soil particles, which in turn affects how nutrients are held and accessed by plant roots.

  • it can dislodge the ions from soil particles, making them more accessible for uptake by the roots.

  • This process is particularly important for nutrients that are essential for plant growth, such as potassium and magnesium, as it enhances their solubility and mobility in the soil.

    • cation exchange

  • altering soil pH and nutrient solubility can significantly improve the availability of these vital nutrients, ultimately leading to healthier plant development and increased agricultural productivity.

  • creating a proton gradient that can be coupled to nutrient uptake via symporters and antiporters, thereby facilitating the transport of cations into plant cells.

Cation exchange in the soil

Nutrient availability

• organic matter in the coil is characterized by a complex mixture of decomposed plant and animal residues, which enhances nutrient retention and provides essential elements for plant growth.

  • as pH declines, organic matter becomes protonated, leading to increased cation exchange capacity, which improves the availability of nutrients such as calcium, magnesium, and potassium for plant uptake.

  • relative cation exchange capacity changes with pH, indicating that optimal pH levels are crucial for maximizing nutrient availability in soils.

Plants can alter nutrient solubility

• shows relative solubility of elements based on pH

• solubility and availability in soil is dependent on the pH, as certain nutrients become more or less accessible to plants depending on the acidity or alkalinity of the soil.

• by acidifying the soil, certain elements become more available to plant roots, enhancing their growth and nutrient uptake.

  • this is because certain elements form insoluble elements at certain pHs, which can limit their availability to plants and hinder overall growth.

Coupled transport of nutrients into root cells

• is essential for maximizing nutrient absorption, as it allows for the simultaneous uptake of multiple nutrients, often facilitated by specific ion channels and transport proteins. This process not only increases the efficiency of nutrient use but also supports the overall health and vigor of the plant.

Nutrient uptake

• Deeper roots

  • Enhanced nutrient availability: By extending deeper into the soil, roots can access a wider range of nutrients that may not be available in the upper layers.

  • especially in desert environments where surface soil often lacks essential minerals due to evaporation and limited precipitation.

• Wider, branched roots

  • : This allows for a more extensive network that can capture nutrients more efficiently and improve overall plant health.

  • Ex. rock corkwood: a drought-resistant tree that has adapted to arid conditions by developing a deep root system to access underground moisture and nutrients.

• no matter what, depletion zones are still being created around the root zone due to the uptake of nutrients, which can lead to competition among plants and affect growth if not managed properly.

Region of the root

• Mature root systems can extend several feet deep, allowing the plant to efficiently absorb water and essential minerals, while also influencing the surrounding soil structure and nutrient availability.

• maturation (‘root hair”) zone: This is where root hairs develop, increasing the surface area for absorption and enhancing the plant's ability to take up water and nutrients from the soil.

• Tip of root: The tip of the root, or the root cap, serves to protect the delicate growing tip as it pushes through the soil, and it also plays a crucial role in sensing gravity and directing root growth downward.

Mycorrhizal fungi

• symbiotic association… fungi paritally penitrates into the root tissue, facilitating the exchange of nutrients, particularly phosphorus, which is often limited in soil. This relationship not only enhances nutrient uptake but also improves the plant's resistance to pathogens.

  • assist w nutrient mineral uptake

    • by extending the depletion zone way beyond where plant can normally reach, mycorrhizal fungi significantly increase the surface area for absorption, allowing plants to access a greater volume of soil and thus more nutrients.

    • also facilitate the uptake of nutrients that plants normally have a hard time getting, such as nitrogen and trace elements, thereby promoting overall plant health and growth.

      • particularly phosphorus, which is often limited in availability due to its tendency to bind with soil particles, making it less accessible to plant roots.

  • get a lot of sugar out of this allowing the fungi to grow even further. This symbiotic relationship benefits both the plants and the fungi, as the plants provide carbohydrates through photosynthesis, which the fungi utilize for energy, while the fungi enhance nutrient availability for the plants.

  • can increase plant growth up to 150%

  • 92% of plant families allow this to happen, demonstrating the widespread importance of mycorrhizal associations in various ecosystems.

  • ectomycorrhizae are a type of mycorrhizal association where fungi form a sheath around the roots of plants, particularly trees, facilitating water and nutrient absorption while also providing protection against pathogens.

  • vesicular-arbuscular mycorrhizae (VAM) are another type of mycorrhizal association, characterized by the formation of arbuscules and vesicles within the root cortex, which enhances nutrient exchange, particularly phosphorus, between the fungi and the plant.

    • branched hyphae that kinda looks like a tree structure extend into the soil, increasing the surface area for absorption and allowing for greater access to water and essential nutrients.

• typical plant will acquire nutrients without this fungi

  • Dischidia major allow ants to use them a refuge… take seeds from plants and disperse the seeds , which can enhance the genetic diversity of plant populations and promote the growth of new individuals in suitable habitats.

  • root system is within the tree that its growing on

Carnivorous plants

• on the surface the lines are all hairs pointing downwards

  • insects will slide down the hairs and the insect can no longer get out bcs the hairs are pointing downwards This adaptation allows the plant to effectively trap its prey, which is then digested for essential nutrients.

• venus flytrap is another example of a carnivorous plant that uses a rapid leaf movement to capture its prey. When an insect touches the sensitive hairs inside the trap, it triggers a quick closure, ensnaring the insect and allowing the plant to absorb nutrients as it decomposes.

  • secrete enzymes to decompose the insect and take in nutrients from the insect while also providing a source of nitrogen and other vital elements that enhance the plant's growth and survival in nutrient-poor environments.

  • mainly take in nitrogen

• Utricularia, commonly known as bladderwort, is another fascinating carnivorous plant that captures prey using specialized bladder-like structures. These bladders create a vacuum that sucks in small aquatic organisms when triggered, allowing the plant to absorb essential nutrients, particularly nitrogen, from its prey.

  • work under a slight vacuum… this causes water and the insect to flow in, which then gets trapped inside the bladder. Once the prey is captured, the plant secretes digestive enzymes to break down the soft tissues, allowing it to efficiently absorb the nutrients released during this process.