Plant growth promotic microorganisms

Question 1

microbiome

Answer 1

Community of microorganisms in a
specific environment (with specific conditions) where they each have a function and interact with each other.

Question 2

phyllosphere

Answer 2

above ground area

Question 3

rhizosphere

Answer 3

below ground area

Question 4

epiphytes

Answer 4

• harmless microorganisms found on the surface of the plant
• nutrient uptake

Question 5

endophytes

Answer 5

• harmless microorganisms found in the inside of the plant
• plant growth and defence

Question 6

edaphic conditions

Answer 6

Soil conditions; pH, nutrient levels, moisture, composition

Question 7

mycorrhizal fungi

Answer 7

Provide phosphorus, nitrogen and water

Question 8

Rhizobia in root nodules

Answer 8

Fix nitrogen from the air in compounds that plants can use as protein building blocks

Question 9

actinomycetes

Answer 9

Inhibit the growth of several plant pathogens

Question 10

drought stress

Answer 10

1) hydrogel formation:
Some microbes produce hydrogels that retain soil moisture, ensuring plants have
access to water even in dry conditions

2) root growth:
Microbes in the rhizosphere boost root
development, helping plants absorb more water from the soil during drought

3) exopolysaccharide production:
Certain microbes produce exopolysaccharides, forming a protective
matrix in soil. This matrix improves water retention, helping plants access moisture during drought

Question 11

salinity stress

Answer 11

1) ion homeostasis:
Metabolites bind excessive salt ions in the soil, preventing them from entering plant roots and causing toxicity

2) osmotic adjustment:
Microbial metabolites like organic osmolytes help plants maintain water balance under salty conditions, preventing dehydration

3) induction of stress-responsive genes:
Metabolites trigger the activation of genes that produce proteins and compounds aiding plants in tolerating salt stress

Question 12

chemical signalling

Answer 12

Plants release molecules like flavonoids into the root zone, attracting helpful bacteria

Question 13

biochemical crosstalk

Answer 13

Once in proximity, plants and bacteria exchange molecular signals, triggering specific responses in each other

Question 14

plant growth promoting bacteria

Answer 14

a group of beneficial soil bacteria that colonise the root surface and promote the plant growth and health via multiple
mechanisms

Question 15

plant growth promotion

Answer 15

1) Biochemical mechanisms: mobilisation and provision of plant nutrients

2) Rhizobacterial interference with plant
phytohormones

3) Release of molecules (VOCs or signaling
molecules) that can impact plant growth

Question 16

nitrogen fixation

Answer 16

Some microorganisms (bacteria or even plants) have the ability to fix gaseous dinitrogen directly from the air into
ammonia usable by plants using the enzyme nitrogenase complex

Question 17

phosphorous solubilisation

Answer 17

achieved by the production of:
- Organic acids: such as acetate; succinate, citrate,…
- Phosphatases
which liberates rthophosphates (simplest form of phosphate) that can be then absorb by plants

Question 18

siderophore production

Answer 18

• The reduction strategy: protons and organic acids are released to decrease the soil pH and thus increasing iron availability
• The chelation strategy: plant roots release
  low-molecular-weight iron-chelating molecules called siderophore that can efficiently bind to iron island then be taken up by root cells

Question 19

phytohormones

Answer 19

chemicals compounds released by plants that promote and influence plant growth

The production of phytohormones leads to root proliferation, thus a higher total root surface, leading to more nutrient absorption

Question 20

quorum sensing

Answer 20

a key mechanism that regulate gene expression in response to the population density, facilitated by the buildup of signaling molecules

is involved in several important processes such as virulence, symbiosis and survival

Question 21

volatile organic compound

Answer 21

some microbes can release VOC’s with
growth-promoting capabilities

Question 22

biological compounds

Answer 22

Microorganisms can synthesize a wide range of compounds resulting in many effects on the plant health

derived from the secondary metabolism

Question 23

microbiota

Answer 23

are the living organisms living in the microbiome

Question 24

biostimulant

Answer 24

any substance or microorganism applied to plants with the aim to enhance nutrition efficiency, abiotic stress tolerance and/or crop quality traits,

• hormone-containing product
• humic substance
• amino acids containing product