Nutrition of Horticultural Crops Exam 3 (Calcium and Magnesium)

Question 1

What is the main source of calcium for plant nutrition?

Answer 1

calcium from dolomitic rocks

Question 2

What are the two processes that liberate calcium from dolomitic rocks?

Answer 2

mining & weathering

Question 3

What types of water sources can become sources of calcium and magnesium to plants, sometimes to their detriment?

Answer 3

alkaline water sources

Question 4

What problem associated with coastal agricultural communities can lead to neutral water sources becoming more alkaline?

Answer 4

salt water intrusion

Question 5

What is the significance of the role plants play in the global cycles for calcium and magnesium as it relates to human nutrition?

Answer 5

plants act as the source of calcium and magnesium for humans (and other animals)

Question 6

As a cation, calcium is weakly attracted to the plasma membrane, and it enters into the cell by means of what?

Answer 6

specific membrane channel powered by a hydrogen ion pump (H+–ATPase)

Question 7

What is the space outside the plasma membrane of the root cell known as that contains calcium which can be made available to the crop?

Answer 7

apoplast

Question 8

What are the three areas in the root that calcium moves through, in the order that they move through them?

Answer 8

(1) area of cell division
(2) area of elongation
(3) area of maturation

Question 9

What part of the plant root has the root chairs?

Answer 9

area of maturation

Question 10

What is the name of the tissue system through which calcium ions can reach other areas of the crop besides the root?

Answer 10

vascular cylinder

Question 11

Why are calcium ions placed in the vacuole soon after entering the plant cells?

Answer 11

maintenance of cell turgidity

Question 12

Calcium ions are moved out of plant cells by means of what, which engage in secondary active transport using the hydrogen ion gradient established by H+–ATPase?

Answer 12

antiport mechanisms

Question 13

What membrane proteins can use ATP energy to actively transport calcium ions out of the cytoplasm?

Answer 13

calcium pumps

Question 14

Is the concentration of cation calcium typically higher in the soil or in the root cell cytoplasm? What is the ratio between these reservoirs?

Answer 14

calcium is typically higher in the soil by a ratio of 1.0 * 10^5 : 1.0

(calcium in the soil ~ 1 mM ;
calcium in the cytoplasm ~ 100 nM)

Question 15

As calcium levels rise (0.5 mM –> 2.0 mM –> 8.0 mM), what would one expect to occur to magnesium concentrations in plant tissues?

Answer 15

magnesium concentrations should decline due to nutrient antagonism

Question 16

As magnesium levels rise (0.5 mM –> 2.0 mM –> 8.0 mM), what would one expect to occur to calcium concentrations in plant tissues?

Answer 16

calcium concentrations should decline due to nutrient antagonism

Question 17

To reduce the chance of a nutrient antagonism, what is the rule of thumb regarding calcium and magnesium concentrations?

Answer 17

plants should have access to three times as much Ca2+ as they have Mg2+ in the soil solution

Question 18

Calcium ions play important roles in (1)______________ defense involving (2)_________ and idioblasts. This makes it vital that the (3)___________ concentrations of calcium are lower than in the apoplast.

Answer 18

(1) extracellular
(2) pectins
(3) cytosol

Question 19

Calcium deficiencies cause cell wall defects. What is a sign of this in plant leaves?

Answer 19

leaf tip necrosis

Question 20

Calcium deficiencies cause cell wall defects. What is a sign of this in apple fruits?

Answer 20

bitter pit

Question 21

Calcium deficiencies cause cell wall defects. What is a sign of this in tomato fruits?

Answer 21

blossom end rot

Question 22

What is the underlying cause of bitter pit in apples and blossom end rot in tomatoes?

Answer 22

a total or near total absence of calcium

Question 23

What are the two roles magnesium plays at the molecular level in plants, both of which are relevant to photosynthesis?

Answer 23

(1) magnesium ions activate RuBisCO enzymes so they can fix carbon dioxide
(2) magnesium is the central atom in a chlorophyll molecule

Question 24

What are phenotypic expressions of magnesium deficiency in plants, which are related to reduced photosynthesis?

Answer 24

(1) leaf bronzing
(2) stunted growth

Question 25

Over (1)____________ time frames and in (2)____________ times, (3)_____________ activity was responsible for spewing sulfur into the atmosphere. Modern (4)__________ combustion alters this.

Answer 25

(1) geological
(2) pre-industrial
(3) volcanic
(4) fossil fuel

Question 26

Sulfur in the atmosphere reacts with water and ozone, forming what?

Answer 26

acid rain

Question 27

What does acid rain pollute crop areas as when introduced to soils with crops?

Answer 27

sulfates (SO42-)

Question 28

Why has acid rain declined as an issue overtime?

Answer 28

the quality of fossil fuels has increased

Question 29

Besides acid rain, what else acts as a source of sulfur to plants?

Answer 29

sulfur from living animals (decomposition and manure)

Question 30

In what form does sulfur first enter the soil from decomposing animals and manure?

Answer 30

amino acids (R group with an “-SH”)

Question 31

What do sulfur atoms break down into in the soil into

Answer 31

elemental sulfur (S)

Question 32

What does elemental sulfur react with oxygen in the sulfur to form?

Answer 32

sulfates (SO42-)

Question 33

Why is sulfur uptake into the plant cell an energy-intensive process?

Answer 33

uptake is facilitated by a symport mechanism, but because it arrives as an ion, it is repelled by the membrane

Question 34

Inorganic sulfur in the form of (1)__________, once in the cytoplasm, becomes attached to ATP by the enzyme (2)_______________. The products of ATPS are (3)_____________, which triggers a chain of other reactions that culminates in (4)_____________.

Answer 34

(1) sulfate
(2) ATP sulfurylase
(3) unstable
(4) cysteine

Question 35

What are three food crops who derive their characteristic flavor from sulfur?

Answer 35

(1) garlic (and other alliums)
(2) horseradish (and other Brassicaceae)
(3) blackcurrants (Ribes nigrum)

Question 36

What are the two classical symptoms of a sulfur deficiency?

Answer 36

(1) generalized yellowing across the plant
(2) stunting of the crop