Question

Mass flow hypothesis was first described by (a) Swanson (b) Buchman (c) Kursanov (d) Munch.

Short answer

The Mass flow hypothesis was first described by (d) Munch.

Step-by-step solution

Understand the Context

The Mass flow hypothesis is a historic concept in plant physiology that explains the mechanism of phloem transport, which is responsible for the translocation of nutrients throughout the plant. Identifying who first described it requires knowledge of plant physiology history.

Identify the Contributor

Through historical records and scientific literature, the Mass flow hypothesis is attributed to a particular scientist. Review the scientific literature or educational resources to determine which of the listed scientists is credited with this hypothesis.

Select the Correct Answer

After researching the origin of the Mass flow hypothesis, it has been found that it was first described by Ernst Munch. Thus, the correct answer is (d) Munch.

Key concepts

Phloem Transport

The phloem is a complex tissue found in vascular plants that plays a pivotal role in the distribution of nutrients. It transports sugars, amino acids, and other essential substances from where they are produced, such as leaves, to other parts of the plant where they are needed, including roots and growth sites.

Central to this process is the movement of a sugar-laden solution called 'sap'. Phloem transport operates on a pressure flow mechanism, where a high concentration of sugars in the source tissue (like leaves) leads to water uptake due to osmosis, creating pressure that pushes the sap down the phloem to sink organs (such as roots and fruits) where the sugar concentration is lower.

Pressure Flow Hypothesis

The mass flow hypothesis, also known as the pressure flow hypothesis, provides an explanation for this process. It suggests that the movement of sap is driven by the difference in pressure potential from the source to the sink. Although more complex interactions are involved, this simplified overview is beneficial for a basic understanding of phloem dynamics in plant physiology.

Plant Physiology

Plant physiology is the study of how various parts of plants function. It spans numerous disciplines, from the study of how plants absorb nutrients and water from the soil, to how they convert light into energy via photosynthesis. At the heart of this field, the mass flow hypothesis integrates concepts from plant anatomy, chemistry, and physics to explain how nutrients move within a plant.

Integrating Concepts

Understanding the mass flow hypothesis demands grasping the intricacies of how phloem and other plant tissues interact. Active and passive transport mechanisms, osmotic pressure gradients, and the function of companion cells alongside sieve tube elements in the phloem all interconnect within plant physiology to facilitate nutrient distribution vital for plant growth and reproduction.

Students studying plant physiology must also comprehend the environmental and biological factors that affect these processes, such as temperature, light availability, soil conditions, and the plant's developmental stage.

Nutrient Translocation

Nutrient translocation in plants encompasses the movement of nutrients from one part of the plant to another. This system ensures that the synthesized nutrients reach all areas of the plant, from the roots deep within the soil to the highest leaf. Phloem transport is central to this system, moving sucrose and other nutrients through the plant's vascular tissue.

Role of the Phloem

The phloem is not isolated in its functions. It works in tandem with the xylem, which is responsible for the transportation of water and minerals absorbed from the soil. Nutrient translocation is vital for maintaining plant health, supporting new growth, and storing energy for periods when production (via photosynthesis) is low, such as during the night or in winter months for deciduous plants.

This intricate balance of nutrient production, transport, and storage is regulated by various plant hormones and signaling molecules that trigger the appropriate responses to internal and environmental cues.