Biology exam 2

What are the three stages of a signaling pathway?

SIGNAL RECEPTION, SIGNAL TRANSDUCTION, RESPONSE.

How do plants perceive light stimuli for growth?

Plants perceive light through phytochromes which absorb light and trigger growth responses such as de-etiolation and phototropism.

What is phototropism?

Phototropism is the growth of a plant toward light.

What is the primary role of auxin in plants?

Auxin promotes cell elongation and is involved in processes like phototropism and gravitropism.

What is the effect of gibberellin (GA) on plant growth?

Gibberellin stimulates stem elongation, seed germination, flowering, and fruit development.

What happens during seed germination in response to light?

Light triggers seed germination by breaking dormancy, allowing the growth to begin.

What distinguishes positive from negative phototropism?

Positive phototropism is growth toward light; negative phototropism is growth away from light.

What are mobile nutrients in plants?

Mobile nutrients are substances that can be moved within the plant, showing deficiency first in older leaves.

What is the role of water potential in plants?

Water potential determines the direction of water movement in plants.

How do plants conduct transpiration?

Plants regulate transpiration through stomatal control and leaf structure.

What is bulk flow in plants?

Bulk flow is the pressure-driven movement of water and solutes through the xylem and phloem.

What is the primary driver of water movement in the xylem?

Transpiration is the primary driver of water movement through the xylem.

What is the function of rubisco in photosynthesis?

Rubisco incorporates carbon dioxide into organic molecules, essential for carbon fixation.

What conditions lead to photorespiration?

Photorespiration occurs under high oxygen and low carbon dioxide conditions.

What is the role of accessory pigments in plants?

Accessory pigments help expand photosynthetic capacity and protect against UV damage.

How does cyclic electron flow differ from non-cyclic electron flow?

Cyclic electron flow involves only PS I and produces ATP, while non-cyclic flow involves both PS II and PS I and produces ATP and NADPH.

How do C4 and CAM photosynthesis help tackle photorespiration?

C4 photosynthesis maximizes CO2 uptake by fixing CO2 in mesophyll cells and transporting it to bundle-sheath cells; CAM photosynthesis fixes CO2 at night, reducing water loss during the day.

What is the significance of the Calvin cycle in photosynthesis?

The Calvin cycle fixes carbon dioxide into organic compounds, producing sugars that serve as energy sources.

How is water absorbed by plant roots?

Water is absorbed by root hairs and can take either apoplast or symplast pathways before reaching the vascular cylinder.

What determines the directionality of xylem versus phloem transport?

Xylem transport is unidirectional (upward), while phloem transport is bidirectional (from sources to sinks).

What can plant leaf symptoms tell us about nutrient deficiencies?

Symptoms in older leaves indicate mobile nutrient deficiencies; symptoms in younger leaves indicate immobile nutrient deficiencies.