Transportation in Plants: Translocation and Transpiration
Have you ever wondered how hydroponic plants drink, feed and move nutrients internally?
This guide explains the basic process of plant transportation, including translocation, xylem, phloem and transpiration in hydroponic growing.
What Is Translocation?
Translocation is the movement of materials from one part of the plant to another.
In hydroponic plants, translocation helps move essential elements through plant tissue as the crop grows, matures and responds to nutrient availability.
Flushing is an excellent example. When flushing mature hydroponic plants, remaining elements in the plant tissues are shifted from the oldest parts of the plant to the newest growth. This relates to nutrient mobility.
During this stage, leaves may rapidly lose chlorophyll pigment and begin showing other pigments, such as carotenoids and anthocyanins, which are flavonoids.
Image Credit: Fuse School
Xylem: Moving Water and Nutrients
Xylem moves water and dissolved nutrients from the root zone through the plant and into the leaves.
Xylem vessels are made up of elongated, dense cells. These cells are impermeable to water and have walls containing lignin, a woody material.
In hydroponic systems, healthy xylem function supports the movement of water and nutrients from the nutrient solution into the plant.
Phloem: Moving Sugars and Amino Acids
Phloem moves sucrose produced through photosynthesis to the rest of the plant. It also works with the supply of amino acids.
Phloem vessels are made up of living cells. They transport sucrose and amino acids up and down the plant.
Image Credit: FS - Xylem & Phloem are found in groups called vascular bundles.
What Is Transpiration?
Transpiration is the evaporation of water from plants.
Plants transpire mainly through the leaves. Leaf stomata open and close to allow the movement of CO₂, or carbon dioxide, and O₂, or oxygen, during photosynthesis.
When a hydroponic plant is over-transpiring, the stomata close to reduce water loss.
In simple terms, transpiration helps plants maintain internal temperature.
Humidity, SVP and Plant Transpiration
The higher the SVP, or saturation vapour pressure, the less plants will transpire. This is because humidity is high.
When humidity is too low, the plant will transpire until the ideal SVP is achieved. If humidity remains too high, the plant may lose turgor and become limp.
Ideal Relative Humidity for Hydroponic Plants
Recommended relative humidity, or RH, ranges:
- Germination: 76–100%
- Vegetative growth: 60–65%
- Flowering: 50–56%
Transpiration in Grow Tents and Grow Rooms
When starting a hydroponic grow from scratch, many growers do not have full climate control and must rely on ambient conditions.
Growing from seed in a grow tent or grow room often creates the same issue: there is very little bio-mass in the environment. For young seedlings, this is a critical stage.
If the environment is not corrected, seedling leaflets may “canoe” or curl inwards. This happens when plants are over-transpiring while trying to achieve the correct SVP.
Summary
Understanding translocation and transpiration in hydroponic plants helps growers manage plant health, nutrient movement, humidity and climate conditions more effectively.
This is a basic introduction to plant transportation. More complex detail can be explored through nutrient mobility, vascular bundles, xylem, phloem, SVP and hydroponic climate control.
