Higher Plant Physiology - Water Stress and Osmotic Adjustment

Flashcards based on the key concepts, details, and physiological mechanisms discussed in the lecture on water stress and osmotic adjustment in higher plant physiology.

What factors contribute to drought injury in plants?

Soil dryness due to lack of rain and low atmospheric relative humidity affecting water absorption.

What physiological symptoms indicate that a plant is under drought stress?

Stunted growth, red coloration at the base, small leaf area, yellowing of leaves, and wilting of young leaves and reproductive organs.

What is the primary effect of drought stress on photosynthesis?

Photosynthesis decreases while respiration increases, leading to reduced plant growth.

How does endogenous ABA influence stomatal closure during water stress?

ABA production triggers physiological responses leading to stomatal closure, thus influencing CO2 absorption.

What role does NCED3 play in ABA biosynthesis during drought stress?

NCED3 catalyzes a key step in ABA biosynthesis, leading to increased ABA accumulation in vascular tissues.

What are the effects of excess light on photosynthesis in plants?

Excess light can induce photooxidation, increase ROS production, and negatively impact photosynthesis-related genes.

What is osmosis, and how does it relate to plant water potential?

Osmosis is the movement of water from a higher water potential area to a lower water potential area, crucial for water transport within plants.

Define osmotic adjustment in plants.

A biochemical mechanism that allows plants to acclimate to water stress by regulating solute concentrations to maintain turgor pressure.

What are the essential components of phloem in angiosperms?

Sieve elements (for transport) and companion cells (which assist in loading and unloading solutes).

What is the difference between source and sink in phloem transport?

Source is where sugars are produced, while sink refers to areas where sugars are consumed or stored.

How does sucrose transport occur from source to sink?

Sucrose is actively loaded into sieve tubes at the source and unloaded at the sink, maintaining concentration gradients.

Describe the process of apoplastic phloem loading.

Sucrose is actively transported against its gradient into sieve elements via a sucrose-H+ symporter.