Plant Physiological Adaptations Quiz

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Questions and Answers

Which tissue types serve as major sinks for carbohydrate import and development?

Roots, tubers, developing fruits, and immature leaves (correct)

Mature stems and leaves

Upper mature leaves and mature fruits

Flowers and seeds

What factor significantly influences the source-to-sink transport in plants?

Size of the root system

Age of the plant leaves

Proximity of the source to the sink (correct)

Number of photosynthetic cells

During the reproductive development of a plant, which sinks typically become dominant?

Mature foliage

Young immature leaves

Fruits (correct)

Root apices

What is an orthostichy in relation to plant vascular systems?

A pattern describing leaf arrangement on a stem Signup and view all the answers

What can alter established translocation patterns in plants?

Interference through wounding or pruning Signup and view all the answers

How do source leaves preferentially supply sinks in the shoot system?

By direct vascular connections Signup and view all the answers

What is the role of anastomoses in translocation pathways?

To serve as alternative pathways in the absence of direct connections Signup and view all the answers

Which statement about leaves and their relation to sinks is true?

Upper mature leaves primarily provide to growing shoots and immature leaves Signup and view all the answers

What is the primary function of xylem parenchyma cells modified as transfer cells?

To retrieve and reroute solutes moving in the xylem Signup and view all the answers

Why are plasmodesmata significant in companion and transfer cells?

They serve as pathways that can carry viruses systemically Signup and view all the answers

What characteristic most distinguishes intermediary cells in plants?

Numerous plasmodesmata connecting them to surrounding cells Signup and view all the answers

What term describes the areas where sap is produced in plants?

Sources Signup and view all the answers

During which phase does the storage root of Beta maritima serve as a sink?

In the first growing season Signup and view all the answers

Which of the following statements about phloem translocation is correct?

Translocation occurs from sources to sinks regardless of gravity. Signup and view all the answers

Which type of cell lacks developed thylakoids and starch grains in their chloroplasts?

Intermediary cells Signup and view all the answers

What is the role of sinks in plant physiology?

To store or metabolize nutrients that are transported from sources Signup and view all the answers

What is the preferred unit for measuring mass transfer rate in sieve elements?

grams per hour per square centimeter (g h–1 cm–2) Signup and view all the answers

Which mechanism of phloem translocation accounts for most of the available experimental and structural data?

Pressure-flow model Signup and view all the answers

What is the range of observed rapid rates of translocation in phloem?

50 to 250 cm hr–1 Signup and view all the answers

In the context of phloem function, what does phloem loading refer to?

Initial transfer of assimilate from leaf mesophyll cells into sieve elements Signup and view all the answers

Which of the following is NOT a factor that a comprehensive theory of phloem translocation must account for?

The role of root hairs in nutrient uptake Signup and view all the answers

Which of the following best describes the role of energy in either sources or sinks during phloem translocation?

Energy is necessary to move photosynthate into the sieve elements in sources. Signup and view all the answers

What type of cytoplasm is present in sieve elements that is important for phloem function?

Active cytoplasm Signup and view all the answers

How do current preferred SI units differ from earlier publications regarding phloem movement?

They use meters or millimeters instead of centimeters. Signup and view all the answers

What effect do sieve plates have on the pressure gradient in sieve elements?

They increase resistance and create a pressure gradient. Signup and view all the answers

Which of the following must be true for effective translocation through sieve elements?

Pores must be clear to prevent high resistance. Signup and view all the answers

What is the effect of low temperature on phloem translocation?

It has no effect on translocation. Signup and view all the answers

What must be true regarding the turgor pressure in sources compared to sinks?

Turgor pressure in sources must be higher. Signup and view all the answers

Which component is primarily involved in phloem loading?

Cytosol converting triose phosphate to sucrose. Signup and view all the answers

What role does P-protein play in sieve elements?

It blocks sieve plate pores if abundant. Signup and view all the answers

What happens to stored starch during phloem loading at night?

It exits the chloroplast as glucose before being converted to sucrose. Signup and view all the answers

What is a key prediction of the pressure-flow model?

Turgor pressure must be higher in source sieve elements. Signup and view all the answers

What is the primary process by which sugars are transported into the sieve elements and companion cells?

Sieve element loading Signup and view all the answers

What is meant by the term 'sieve element–companion cell complex'?

A functional unit for loading sugars into phloem Signup and view all the answers

In the context of phloem transport, what is the main role of sink organs?

To store or metabolize sugars Signup and view all the answers

What is the process by which sugars leave the sieve elements in sink tissues known as?

Sieve element unloading Signup and view all the answers

Which of the following correctly describes the relationship between source and sink processes?

Sink processes essentially reverse the events that took place at the source Signup and view all the answers

Which step follows sieve element unloading during the import of sugars into sink cells?

Short-distance transport Signup and view all the answers

What process determines the total amount of fixed carbon available for translocation?

Photosynthetic rate Signup and view all the answers

What is involved in the regulation of the diversion of fixed carbon into various metabolic pathways?

Allocation of fixed carbon Signup and view all the answers

What primarily determines sink strength in a plant?

Sink size and sink activity Signup and view all the answers

Which of the following activities can limit the rate of uptake by a sink?

Unloading from sieve elements Signup and view all the answers

What does the term partitioning refer to in the context of plant vascular systems?

Differential distribution of photosynthates within the plant Signup and view all the answers

How does cooling a sink tissue affect photosynthate transport?

It decreases the speed of transport towards the sink Signup and view all the answers

Which enzyme is NOT mentioned as influencing sink strength?

Starch phosphorylase Signup and view all the answers

What is an observed effect of a mutant corn plant with a defective enzyme for starch synthesis?

It has reduced transport of material to the kernels Signup and view all the answers

Sink size is defined as which of the following?

The total weight of the sink tissue Signup and view all the answers

What is NOT a factor affecting sink activity?

Transpiration rate from source leaves Signup and view all the answers

Study Notes

Translocation in Phloem

Phloem is the vascular tissue responsible for transporting sugars (assimilates) from source (e.g., leaves) to sink (e.g., roots, fruits)
The source is where sugars are produced (e.g., during photosynthesis)
The sink is where sugars are used or stored
Sucrose is the main transported sugar in phloem
Sieve elements are essential in phloem translocation
Companion cells are closely associated with sieve elements, and play a vital role in the transport process
Sieve tube elements and companion cells are together referred to as sieve element-companion cell complex
Sieve elements are highly specialized cells, losing many cellular components during differentiation
Companion cells are involved in metabolic and transport functions for sieve elements
Transfer cells have finger-like wall ingrowths to enhance solute exchange
Phloem loading is the active transport of sucrose into the sieve elements
Phloem unloading is the removal of sugars from the sieve elements into sink cells
The pressure-flow model describes translocation through pressure differences generated by sugar loading and unloading in the sieve elements
Water moving into sieve elements at the source creates pressure for mass flow from source to sink
The rate of translocation is influenced by both size and activity of the sink

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Description

Test your knowledge on plant physiology with this quiz focusing on carbohydrate import, transport mechanisms, and the development of sink tissues. Explore concepts like source-to-sink transport and the role of vascular systems in plants. Perfect for biology students and plant science enthusiasts!