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Animations:

Phosphorus in Surface Waters


This animation demonstrates the four forms that phosphorus (P) can take in surface water, and how the equilibrium between the forms can be upset and then rebalanced.

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Lessons:

Auxin and Auxinic Herbicide Mechanism(s) of Action - Part 1 - Introduction

The selective control of broadleaf weeds in cereal grain crops by auxinic herbicides has made this group one of the most widespread and important herbicide families in use. These herbicides were the f

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Plant and Soil Sciences > Plant Physiology > Lessons List
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Foliar Absorption and Phloem Translocation (Beginner Level)

Herbicides must be absorbed into plants in order to be effective. Herbicide absorption can occur through leaves, roots or both. The process by which herbicides kill weeds, called mode of action, requires herbicide absorption and may also require herbicide movement or translocation within the plant. Translocation means that the herbicide moves from the site of absorption to some other plant part. Foliar applied herbicides that have the necessary characteristics to move in the phloem will translocate to areas of the plant that are actively growing; however, not all foliar-applied herbicides move from the leaves that intercepted the spray solution. Herbicides that are absorbed but not translocated are called contact herbicides, while herbicides that translocate to shoot or root meristems are called systemic herbicides. Absorption and translocation of xylem mobile herbicides will be discussed in another lesson.


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La Transpiración - Movimiento del Agua a Través de las Plantas (Beginner Level)

La transpiración es la pérdida de agua en forma de vapor por las plantas. El agua es absorbida del suelo por las raíces y transportada en forma líquida por el xilema hacia las hojas. En las hojas, unos pequeños poros permiten que el agua (H2O) escape a la atmósfera en forma de vapor, al tiempo que se permite la entrada de bióxido de carbono (CO2) para la fotosíntesis. De toda el agua absorbida por las plantas, menos del 5% es retenida y utilizada para crecimiento y almacenamiento. En esta lección se explicará porque las plantas pierden tanta agua, la ruta que ésta sigue dentro de la planta, como pudieran las plantas controlar la pérdida excesiva de agua y como las condiciones ambientales influyen en la pérdida de agua por las plantas.

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Root Absorption and Xylem Translocation (Beginner Level)

Overview: Herbicides must be absorbed into plants in order to be effective. Plant roots and below ground shoots have few barriers to herbicide absorption; however, interactions with soil particles and soil organic matter have significant impacts on the amount of herbicide available for plant absorption. Plant roots and below ground shoots (hypocotyls or coleoptiles) are lipophilic by nature and do not have thick, waxy cuticles like leaves. Lipophilic and hydrophilic herbicides reach the root surface by bulk transport in soil water; however, there are a few examples of herbicides that reach the root as a vapor or gas. Soil-applied herbicides can translocate to the shoot or remain in the root system. Soil-applied herbicides translocate to the shoot in the xylem and tend to accumulate in mature leaves that transpire the most water. The lipophilic/hydrophilic nature of the herbicide will determine if the herbicide translocates to the shoot. Absorption and translocation of phloem-mobile herbicides will be discussed in another lesson.

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Transpiration - Water Movement through Plants (Beginner Level)

This lesson and its animation follows the journey of water through a plant from its uptake by roots to its evaporation from the leaf surface. How this journey is altered by plant characteristics such as stomata and cuticles as well as by changes in the environment will be described.

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