🚶‍♀️ Transport in Flowering Plants 🌱

Plants require a transport system to:

• 💧 Carry water and mineral salts from roots to other parts.
• 🍃 Transport food manufactured in the leaves to other parts.
• 💪 Distribute hormones from sites of synthesis to sites of usage.

🔬 Vascular System

This system, known as the vascular system, consists of xylem 🪵 and phloem 🌾 tissues, which are associated with cambium, a meristematic tissue that produces new xylem and phloem cells through cell division.

🌿 Xylem

Conducts water 💧 and minerals from roots 🌱 to other plant parts, also providing mechanical support 💪.

🍁 Phloem

Transports manufactured food (mainly sugars 🍭) from the leaves 🍃 to other plant areas.

Root hairs near the root tips absorb water and minerals. Root hair cells are adapted for absorption by:

• 🔍 Having elongated outgrowths that increase surface area.
• 🚫 Lacking chloroplasts to create space for absorption.
• ⚡ Containing many mitochondria for active transport of minerals.

Water travels up the plant 🌿 in a continuous stream, known as the transpiration stream 🌊, through xylem vessels. This is facilitated by several forces:

• 💨 Transpiration: The diffusion of water vapor from leaves 🍃 to the atmosphere 🌬️ through stomata.
• 💧 Capillarity: Movement of water into narrow spaces in the xylem due to cohesion and adhesion.
• 🔴 Root Pressure: Pressure in the xylem from water absorbed by the roots 🌱.

💧 Transpiration

Transpiration is the diffusion of water vapor from leaves 🍃 to the atmosphere 🌬️, mainly through stomata on the underside of leaves. Water moves from xylem vessels to mesophyll cells by osmosis, evaporates into air spaces, and finally diffuses out through stomata.

❌ Types of Wilting

Excessive transpiration can lead to wilting, a condition where plant cells lose water 💧, causing leaves 🍃, flowers 🌸, and young stems to sag. Types of wilting include:

• ⏳ Temporary Wilting: Reversible by providing water 💦.
• ☠️ Permanent Wilting: Irreversible, leading to plant death 💀.

🌡️ Factors Affecting Transpiration Rate

Various factors influence the rate of transpiration 🌬️:

• 🌞 Temperature: Higher temperatures increase water molecule kinetic energy, raising transpiration rates.
• 💨 Humidity: High humidity reduces the concentration gradient, slowing transpiration.
• 💡 Light Intensity: High light causes stomata to open, increasing transpiration.
• 🌬️ Wind: Wind removes the water vapor layer around the leaf 🍃, increasing transpiration.

🌵 Adaptations to Reduce Transpiration

Plants reduce water loss through specific xeromorphic features, such as:

• 💧 Thick waxy cuticles.
• 🔽 Sunken stomata.
• 🌲 Needle-shaped or reduced leaves.
• 🌿 Leaf hairs.
• 🌬️ Ability to roll leaves in dry conditions.

Translocation is the movement of manufactured food from its source (usually leaves 🍃) to sink sites (areas of usage or storage) through the phloem 🌾. Key translocated substances include sucrose 🍬 and amino acids 🍴 dissolved in water 💧.

🧪 Evidence for Translocation

• 🐜 Aphid Experiment: Anesthetizing a feeding aphid reveals a liquid containing sugars 🍬 and amino acids from the phloem 🌾.
• 🪓 Ringing Experiment: Removing a ring of bark (and phloem 🌾) causes swelling above the ring, indicating food transport in phloem.
• ⚛️ Radioactive Carbon Tracing: Plants exposed to radioactive CO₂ produce radioactive sugars 🍬, which trace translocation pathways in the phloem 🌾.

Plants convert manufactured food into starch or oils 🧈 for storage in various modified organs:

• 🍠 Root Tuber: A lateral root swollen with food (e.g., sweet potato 🍠).
• 🥔 Stem Tuber: An underground stem with stored food (e.g., Irish potato 🥔).
• 🧅 Bulb: Fleshy leaves surrounding a short stem (e.g., onion 🧅).
• 🌱 Rhizome: A horizontal underground stem (e.g., ginger 🌱).
• 🌷 Corm: A swollen underground stem (e.g., Crocus 🌷).
• 🌰 Seed: A structure containing an embryo and food storage, protected by a testa.