Environmental deficiencies​

Question 1

Describe Stress

Answer 1

Adverse force or influence that tends to inhibit normal systems from functioning optimally ​
Any external constraints that limits fitness/productivity below the genetic potential of the plant​
Factor that results in physical or chemical damage to plant body or metabolism​

Question 2

What are nitrogen, phosphorus and sulfur

Answer 2

These are macronutrients and Part of carbon compounds (amino acids, nucleotides, enzymes cofactor…)​

Question 3

What about phosphorus and calcium

Answer 3

They are macronutrients and important in structural integrity (in membranes and cell walls) and/or energy storage.​

Question 4

What about Boron

Answer 4

Boron is an essential element for vascular plants

Question 5

Which elements present as ions dissolved or bound to biological compounds. Roles as enzyme cofactors, regulation of osmotic potential and messenger.​

Answer 5

potassium, magnesium, calcium (macro)
manganese, chlorine and zinc (micro)

Question 6

Which are metals involved in redox reactions, in particular for electron transport.​

Answer 6

iron, nickel, manganese, copper and molybdenum

Question 7

How do you know that a nutrient is essential?​

Answer 7

When without it the plant doesn’t reach reproductive stage

(chlorine hard to tell)

Question 8

Explain what Potassium ​does in the plant

Answer 8

K+ activates more than 50 enzymes, including some involved in protein synthesis and photosynthesis.​

K+ acts counteracts proton charges across the thylakoid created by the proton gradient necessary for ATP synthesis.​

maintains cation-anion balance
regulation of stomatal movement

Question 8

Describe some deficiency symptoms​

Answer 8

Reduction in growth: Zn, N, P, S, K​
Chlorosis (yellowing of leaf due to lack of chlorophyll): N, Mg, Fe, Zn, Mo​
Necrosis: Cu, Zn, K, Ca​

Question 9

Avoiding deficiencies with fertilizers: limitations and drawbacks​

Answer 9

To avoid N, P and K deficiencies and maximise yield, farmers often use fertilizers.​

Fertilisers are costly and small scale farmers in developing countries often cannot afford them​
Industrial N fixation requires lots of energy​
Nitrogenous fertilisers release greenhouse gas NO​
Fertiliser leaching (N and K) leads to eutrophication​
Phosphorous is a non renewable, finite resource​

Question 10

Acclimations to nitrogen availability​

Answer 10

Studying the effect of nutrient concentration in artificial growth media ​
The split root system indicates that plants increase lateral root growth in regions with higher nitrogen concentration.​ however sometimes they grow more roots when there is more nitrate to take up, so depending on the experiment you may get different answers.

remember soil is heterogeneous

Question 11

Acclimations to phosphate availability​

Answer 11

Inhibition of primary root growth
Increase in root hair length and number
Enhanced formation of lateral roots
Increase in lateral root length

more pi in top soil than deep so roots will grow more laterally (more branching)

Emergence of tertiary lateral roots in lupin​
Development of proteoid roots in lupin​

Question 12

Acclimations to potassium availability​

Answer 12

Root hair length of seven different crops grown in containers with soils with moderate or low potassium levels​
Several crops have longer root hairs when there is a low K+ concentration in the soil.​

The response to low K+ concentration in the soil in terms of root length varies between species.​

(not as certain)

Question 13

What are some adaptations to low nutrient availability

Answer 13

symbiosis with soil microorganisms-mycorrhizae facilitate access to nutrients in exchange for carbohydrates.

Plants get fixed nitrogen while the rhizobia (bacteria) get carbohydrates and a sheltered environment

Root system adaptations​-Large root biomass and surface area (lateral rooting, root hairs) , More cortical aerenchyma​.

what you invest in roots there is a trade off and it is at the expense of the shoot

some cyanobacteria can also have symbiosis such as with giant rhubarb

depending on what is deficiency, the roots will grow differently e.g P deficiency= more branched more shallow roots whereas N deficiency=roots go deeper (As N is more soluble and goes deeper into the soil)

Question 14

Adaptations to low nutrient availability​ in carnivorous plants

Answer 14

Proportion of nitrogen provided by preys in five plants of Drosera Rotundifolia in three different habitats​

Question 15

Describe Phototropism​

Answer 15

Moving towards the light​
Light is perceived at the tip of the plant and induces the production of auxin. Auxin is transported downwards and towards the side less exposed to light. The auxin gradient promotes growth on that side and results in curvature towards the light.​

In Arabidopsis seedlings with altered auxin transport the curvature is modified.​

Question 16

Shade avoidance​ (adult plants)

Answer 16

Growing above the canopy​. Shade avoidance is the response of sun-loving plants to other plants growing over them.​

The way plants detect that a plant is growing above them is is the lights coming through.
Under the canopy is enriched for far-red light wavelengths because leaves filter red and blue light.​

Shade avoidance responses include growing taller instead of branching, expand leaf blade and petiole, elevate leaf angle and flower earlier.​

Question 17

Oxygen deficiency​

Answer 17

Lack of oxygen (hypoxia/anoxia) impairs respiration: oxygen-deprived organs have to rely on fermentation to produce energy. ​

Development of aerenchyma​ for Buoyancy as well as forming a spongy tissue that creates spaces or air channels in the leaves, stems and roots of some plants, which allows exchange of gases between the shoot and the root

damage occurs when the oxygen comes back

Schoenoplectus tabernaemontani​
Hippuris vulgaris​
(rice)

Question 18

What can plants do to get what they need to grow and survive?​

Answer 18

Adapt their growth pattern: ​
Expand roots to absorb essential nutrients​
Increase shoot height and width and grow in the direction of light​
Develop aerenchyma​

Interact with other living beings: ​
Collaborate with microorganisms to get nutrients​
Eat insects​
Outcompete neighbours for light​

Many of these strategies require that plant to reliably detect the availability of environmental resources​
e.g. photoreceptors, nitrate sensors​

Question 19

What are Dauciform roots?

Answer 19

in Cyperaceae and they are short lateral roots