plant physiology

Phloem:
- high conc of _

- under (+/-) pressure

- high conc of sugars

- under positive pressure

Fruit ripening is controlled by , which activates the transcription of genes that break down _ _

ethylene activates the breakdown of cell wall

The effect of phytohormones depends on (5)

• concentration

• tissue

• organ

• stage of development

• plant species

Glutamine synthetase

incorporates NH4+ into an organic molecule (glutamate)

Hydroponic culture

allows for plant nutrition studies to determine the essentiality of a nutrient

Nitrate absorption occurs

across the plasma membrane via specific symporters

The main ions involved in stomatal opening:

Cl- and K+ entering the vacuole of guard cells

The most readily available form of nitrogen for plants is

nitrate, an essential macronutrient that is very stable and abundant in the soil

Stomatal opening occurs

through the activation of the ATPase pump in guard cells, which causes K and Cl to enter the guard cell from the companion cell, leading to the entry of water into the guard cell

Regarding essential elements

the plant absorbs an available form called a nutrient

In the nodule, rhizobia fix nitrogen and transfer it to the plant in exchange for

a carbon source from the plant

Nitrate reductase

reduces NO3- and NO2-

Differentiation processes involve

changes in gene expression

Sucrose

is loaded into the sieve tubes at the expense of ATP

In long-distance phloem transport

the sieve tubes at the source are loaded with sucrose, which increases their water potential

Pair of phytohormones that control seed germination

gibberellins/abscisic acid

Water potential indicates

the direction in which water moves between two compartments

Regarding essential mineral elements

an essential element cannot be replaced by another; it is directly involved in the plant’s metabolism; if the element is deficient, the plant cannot complete its life cycle

Pair of phytohormones that control systemic defense

salicylic acid/jasmonic acid

The plant growth regulator that controls elongation at the stem internodes is:

gibberellins

Plant growth refers to an increase in:

the number and size of cells

The ability of plant cells to differentiate into other cell types is called

totipotency, and only cells with a nucleus possess this ability throughout their entire life cycle

Cavitation occurs

when the water potential difference between the aerial parts and the soil is very high

The value of the osmotic potential is always negative, which means that:

solutes retain water, that is, they decrease the free energy of water

Chlorosis in leaves is:

yellowing of the leaf without cell death

Nitrogen transport within the plant occurs:

through the xylem, in the form of amino acids and nitrate, moving upward

The initiation of infection of legume root cells by rhizobia is due to the recognition of molecular signals:

plants emit flavonoids that the rhizobia identify and “respond” to with lipopolysaccharides (nod factors)

Nitrate assimilation consists of:

reduction of NO3- to NH4+ and subsequent incorporation into glutamate to form glutamine

Nitrite reductase:

is an enzyme present in the plastid; it uses ferredoxin (Fd) as a reducing agent and reduces NO2- to NH4+

Guttation:

the appearance of droplets on the edges of leaves in the early morning

Photosynthetic pigments are:

photoreceptors that contain chromophores capable of absorbing light energy

Regarding water absorption by the root:

the Caspary strips prevent water from passing into the xylem through the apoplast

Osmotic potential:

is a negative component because dissolved solutes decrease the water potential of the water

Water potential

Indicates the direction in which water moves within a system

How does water move from the root (base of the xylem) to the aerial parts of the plant?

By a water potential gradient, maintained by transpiration, along with capillarity.

The main ions involved in stomatal opening are:

Cl- and K+, which enter the vacuole of the guard cells

Stomatal opening is determined by:

increases in cell volume due to the entry of ions into the vacuoles of guard cells, which reduce their water potential.

Cavitation occurs:

when the difference in water potential between the aerial parts and the soil is very high.

If the concentration of ABA increases in the guard cells:

the stomata close due to inactivation of the ATPase pump in the guard cells

In the rhizobium-legume symbiosis, the first event is recognition between the plant and the bacterium. This occurs because:

the plant releases flavonoids that induce the expression of Nod genes in the bacterium.

Loading of the phloem occurs via:

companion cells, which possess specific H-ATPase pumps and specific sucrose transporters

In phloem transport:

at the source, the passage of sucrose into the sieve tube triggers the movement of water from the xylem to the phloem due to a difference in water potential

80% of the phloem’s content consists of sugars:

sucrose is the primary non-reducing sugar transported by the phloem

Regarding the plant’s acquisition of essential elements, we can state that:

the plant absorbs an available form called a nutrient, which crosses the plasma membrane via transporters

An essential element is one that:

cannot be replaced by another essential element

Macronutrients:

are just as essential as micronutrients

Which of the following functions is NOT characteristic of essential elements?:

maintaining the pH at values close to neutrality

Necrosis is a symptom of essential element deficiency that manifests as:

cell and tissue death, primarily at the leaf level

Nitrogen is an essential element that:

is absorbed primarily in the form of nitrate through a symport-type cotransport

NO3- in the plant:

is first reduced to NO2- (in the cytoplasm) and in a second step to NH4+ (in the plastid)

Nitrification involves:

the oxidation of ammonium to nitrite and then to nitrate, which occurs in the soil through the action of microorganisms

Regarding the movement of nitrogen within the plant:

NO3- is transported through the xylem

Reaction with nitrogen carried out by the nitrogenase complex

N2 + 18NADPH + 12H+ + 10e- -> 2NH4+ + 6H2 + 18NADP+

In nitrogen assimilation in the plant, energy (ATP) is consumed in the following steps:

in ammonium assimilation, in the step catalyzed by glutamine synthetase

In rhizobium-legume symbiosis, there is an exchange of:

sucrose from the photosynthetic zone to the nodule and nitrate from the nodule to the photosynthetic zone

Which of the following statements is true?:

Development involves phenomena of cell growth and differentiation

In general, we can state that the reversible inactivation of hormones occurs through:

glycosylation

Plant growth regulators are characterized, among other things, by:

the response depends on their concentration and the sensitivity of the tissue in which they act

Short-distance auxin transport:

is slow and occurs from cell to cell via specific transporters

According to the acid growth hypothesis:

auxins cause the acidification of the cell wall by activating expansins that break down cellulose

To increase sucrose production, we aim to lengthen the internodes of sugarcane stems. Which hormone would you use?:

gibberellins

The pair of phytohormones that controls the branching pattern of roots and stems is:

auxins/cytokinins

During germination, gibberellins:

are synthesized by the embryo, and their target tissue is the aleurone layer

Red light converts the inactive form of phytochrome (Pr) into

the active form (Pfr), triggering a light-dependent response

The following molecule corresponds to a

An auxin

The following molecule corresponds to a

A cytokinin