Flashcards on Plant Physiology: Translocation in the Phloem

These flashcards cover key concepts and details about translocation in the phloem based on lecture notes.

The tissue that translocates the products of photosynthesis (sugars) is called __.

Phloem

The method through which phloem translocation occurs, driven by osmotically generated pressure gradient between source and sink, is known as the __.

Pressure flow model

In phloem, photosynthetic products are transported from mature leaves to areas of __.

growth and storage

Companion cells assist sieve elements by providing __ and possibly other compounds.

ATP

The __ are the specialized cells that conduct sugars and organic materials in the phloem.

Sieve elements

Two types of sieve elements in seed plants are sieve tube elements and __.

sieve cells

Sieve tube elements are typically found in __, while sieve cells are found in gymnosperms.

angiosperms

Callose plays a role in the repair of damaged sieve tubes by forming a __.

plug in the sieve pores

The main types of compounds translocated in the phloem include sugars, amino acids, hormones, and __.

inorganic ions

The most commonly transported sugar in the phloem is __.

sucrose

Phloem loading refers to the movement of __ from mesophyll cells to sieve elements of mature leaves.

photosynthates

The __ pathway for phloem loading involves sugars entering the apoplast before loading into phloem.

Apoplastic

The __ pathway for phloem loading involves sugar movement through the symplast via plasmodesmata.

Symplastic

Sucrose loading in apoplastic loading is facilitated by a __ symporter.

sucrose-H+

Active transport of sugars during apoplastic loading in sieve elements requires __.

ATP

Flooding or cold temperatures can impact the __ of phloem translocation in herbaceous plants.

efficiency

In phloem, the transition from source to sink typically occurs between and percent leaf expansion.

25, 50

The tissue responsible for storing materials, such as starch or proteins in phloem, is called __.

Parenchyma

The pressure-flow model explains that the flow of phloem sap is driven by a __.

pressure gradient

In addition to sugars, phloem can also transport signaling __ between cells.

molecules

Phloem unloading is the process of importing sugars into __.

sinks

Aphids use their __ to collect phloem sap, acting like a natural syringe.

stylet

The large pores found in sieve tube walls facilitate the transport of __.

sugars and other compounds

Companion cells are vital to the function of sieve tube elements because they perform __ and transport assistance.

protein synthesis

P-proteins are structural proteins that help to __ sieve plate pores in angiosperms when damaged.

plug

Sieve tube elements have __ cell walls, allowing for more efficient flow of phloem sap.

non-lignified

Companion cells and sieve tube elements form a functional unit referred to as the __ complex.

sieve element-companion cell

In the phloem, when sugars are actively loaded into sieve elements, it results in __ pressure.

high turgor

Phloem is generally found both external and internal to the __.

xylem

Long-distance transport systems in plants evolved for efficient exchange of __ products.

photosynthesis

Phloem unloading requires metabolic energy to transport sugars to cells in __ tissues.

sink

The __ model describes how raffinose and stachyose are formed during symplastic loading.

polymer trapping

Phloem translocation rates can be affected by changes in __ and stress responses.

turgor pressure

In phloem, movement of sucrose from source to sink primarily occurs through __ elements.

sieve tube

The __ of phloem sap is influenced by the metabolic needs of developing tissues such as roots and fruits.

composition

During symplastic loading, sucrose is synthesized from UDP-glucose and __.

fructose 6-phosphate

Phloem unloading can occur through both symplastic and __ pathways.

apoplastic

Callose is deposited in response to __ or stress, helping to seal sieve pores.

damage

The __ flow of water and solute occurs from source to sink in the pressure flow model.

pressure-driven

Photosynthate distribution involves the differential allocation of fixed __ in the plant.

carbon

Within the phloem, the __ transport system also includes amino acids and RNAs.

signaling molecule

Photosynthesis occurs in __, where sugars are produced and then translocated via phloem.

leaves

Sieve plate pores typically have diameters ranging from to micrometers.

1, 15

In mature sieve tube elements, companion cells aid in __ and translocate photosynthetic products efficiently.

transport

Sucrose is formed from two monosaccharides: glucose and __.

fructose

Phloem translocation velocity can range from to m h-1.

0.3, 1.5

Plants with abundant __ have increased efficiency in transporting sugars and other nutrients.

plasmodesmata