Chapter 36, 37

Plants and their mutualistic relationship with Root Nodules (bacteria) and Mycorrhizae (fungi)

- Plants need fixed nitrogen (N2-->NH3) which are normally provided by bacteria (such as nitrosomonas) that can do so. - Some plants (mostly legumes) are involved mutualistic with nitrogen fixing bacteria (like Rhizobium). These bacteria in the nodules that are along side the roots which provide fixed nitrogen to the plants. - Mycorrhizae wraps around the roots increasing surface area to provide plants with water and nutrients while the plant provides photosynthates to the mycorrhizae.

How do plants regulate transpiration?

-Guard cells regulate the opening and closing of stomata and therefore transpiration. • When water is abundant, it flows into the guard cells, making them TURGID and OPENING the stomata • When water is in short supply, the guard cells are NOT TURGID, and the stomata CLOSES.

What us humus and why is high humus content optimal for plant nutrition?

-Humus consist of organic decaying matter which is a main source of mineral nutrients in soil. -Inc surface area (no leaching) -keeps the soil porous and aerated.

How can one determine if an element is essential? How many essential elements are there?

-Hydroponic Culture can be used to determine which elements are essential. -There are 17 elements that are essential for plants. (9 are macronutrients and 8 are macronutrients) Note: Macronutrients and Micronutrients are EQUALLY important.

Root cortex structure and pathways.

-In the root cortex the cytoplasm and cell walls are continuous from cell to cell. -The cell wall continuum is called the apoplast - The cytoplasmic continuum is called the symplast • Plasmodesmata are channels that connect the cytoplasm of neighboring cells There are 3 pathways 1. Apoplastic route 2. Symplastic route 3. Transmembrane route

Nutrient Deficiencies

-Magnesium is a component of chlorophyll so a deficiency results in chlorosis (yellowing). -Deficiencies of mobile nutrients affect older organs. (younger tissues get nutrients) -Deficiencies of relatively immobile nutrients affect younger organs. (older tissue gets nutrients) -Deficiencies of nitrogen, phosphorous, and potassium are most common in plants

Absorption of water by roots

-Root cells have a lower water potential than the surrounding soil. -This is due to the root's negative pressure potential (tension) - Water flows from the soil into the roots

What does soil contain?

-Sand (biggest) -Silt -Clay (small) -Humus (Decaying organic matter)

Optimal Soil Characteristics of sand, silt, and clay. What type of soil is the most productive and fertile?

-Sand has large spaces enabling diffusion of O2, but water and minerals are leached (plants cannot obtain) -Silt and clay have small spaces therefore water and minerals are NOT leached. However soil becomes saturated and O2 levels decrease. -Loam is the best soil. (equal mixture of everything)

Optimal Soil Characteristics—pH

-Soil particles and humus are negatively charged (anions) - majority of a plant's essential inorganic nutrients are positively charged (cations) Note: Nutrients will adhere to the soil - Acidic soil has high +H concentration (bad), as a result nutrients (cations) get leached not being available for p -Neutral/Slightly basic soil is best

Loading sugars into sieve tube

-Sugars are transported within the phloem's sieve tube members from sugar source (leaves) to sugar sink. A storage (like roots) can be a source and sink -Sugars are loaded into sieve tube members at the source - Because sugar concentration is high within the phloem at the source yet sugar is still being loaded into the phloem, sugar moves against its concentration gradient (active process) Phloem sap is water + photosynthates

Innermost layer of the root cortex

-The innermost layer of the root cortex is the endodermis -The endodermis cell walls are encircled by a layer of suberin called Casperian lipid -The Casparian strip prevents appoplastic entry into the xylem. Also ensures water does not flow back out.

Transpirational pull is facilitated by...

-Transpirational pull is facilitated by the cohesion and adhesion of water molecules in the xylem • Cohesion = water molecules sticking to a each other (Hydrogen bonding) • Adhesion = water molecules sticking to the xylem cell wall. -Cohesion and adhesion counter the force of gravity

Water potential

-Water flows from regions of higher water potential to regions of lower water potential • Ψ = 0Mpa for pure water at sea level and room temperature -Formula is (-Ψ=ΨS +ΨP) - Adding solutes decreases ΨS and therefore Ψ. - ΨP can be negative • Negative pressure potential is called TENSION occurs in nonliving cells (xylem cells) - ΨP can be positive • Positive pressure potential is called turgid pressure • This occurs in living cells (phloem cells)

An Overview of Resource Acquisition and Transport

-Xylem sap (water and minerals) are transported (upward) from roots to shoots. -Phloem sap can flow (upward/downward) from sites of sugar production to sites of sugar use. -Transpiration is when water is loss through the leaves. (this creates a force)\ - Gas exchange happens in roots (take in O2 and release CO2) and in leaves (take in CO2 and release O2).

Optimal Soil Characteristics—Living Organisms and water

-living organisms (insects and roots) are needed to decomposition and soil mixing. -Minerals are dissolved in solution so water is need, but scarce or extreme amounts of water can be damaging.

Pressure Flow Mechanisms

1. Adding solutes (active process) decreases ΨS, overall decreasing water potential . 2. As a result of water potential decreasing H2O will rush into sievetubes (phloem) from xylem vessel. Due to water rushing in this it creates + ΨP (turgid). 3. + ΨP (turgid) pushes the phloem sap away from the sugar source (leaf) to a sugar sink (root for storage). Note: Phloem is highly concentrated and the storage unit is low concentrated, so sap will passively go into the storage unit. (remember going down the concentration gradient is passive) 4. Sugar is now loss (due to storing it) in phloem and H2O is abundant (lowers ΨS). Now vessel xylem will have a lower water potential than the phloem. So H2O diffuses back into the xylem. (cycle complete) Note: Excluding the loading of sugar, the mechanism is passive.

Who do plants form mutualistic and non-mutualistic relationships with?

Mutualistic with: Root Nodules (bacteria) and Mycorrhizae (fungi) NON-Mutualistic: Parasitics plants and carnivorous plants.

Plants and their NON mutualistic relationship with Parasitics plants and carnivorous plants.

There are 2 types of parasitic plants 1. Hemiparasites can photosynthesis but still receive additional nutrients from the host 2. Holoparasite can NOT photosynthesize so they fully depend on their host for nutrients. -Carnivorous plants are photosynthetic but supplement their supply nitrogen by trapping and digesting insects or other small animals (modified leaves). Note: there are 3 types of carnivorous plants 1.Venus flytraps 2.Sundews 3.Pitcher plants

The movement of sugar within a plant, from source to sink, is referred to as...

Translocation

cohesion tension mechanism

• Water vapor saturates the leafs spongy mesophyll -Plants lose water by way of transpiration (Water flows down its water potential gradient). This creates -ΨP in the leaf. - Tension (-ΨP) in the leaf exerts a pulling for on the xylem and this pulls water back into the leaf. • Water is pulled upward by negative pressure (tension) in the xylem -The transpirational pull on xylem sap is transmitted from the leaves down the stem to the roots (and into the surrounding soil) Note: Leaf ΨP < Root ΨP - PASSIVE (NO ENERGY) water is flowing down its concentration gradient.