Nutrient Deficiencies in Horticultural Crops

Question 1

What are the macronutrients plants require for their adequate growth?

Answer 1

nitrogen (N)
phosphorus (P)
potassium (K)
magnesium (Mg)
calcium (Ca)
sulfur (S)

Question 2

What are the micronutrients plants require for their adequate growth?

Answer 2

copper (Cu)
iron (Fe)
manganese (Mn)
zinc (Zn)
boron (B)
chlorine (Cl)
nickel (Ni)
molybdenum (Mo)

Question 3

What are the mobile plant nutrients? In what forms are they mobile within plants and soils?

Answer 3

nitrogen (NO3-, NH4+)
phosphorus (H2PO4-)
potassium (K+)
magnesium (Mg2+)
molybdenum (MoO42-)

Question 4

What are the immobile plant nutrients? In what forms are they mobile within plants and soils?

Answer 4

calcium (Ca2+)
sulfur (SO42-)
copper (Cu2+)
iron (Fe2+)
manganese (Mn2+)
zinc (Zn2+)
boron (H3BO4)
chlorine (Cl-)
nickel (Ni2+)

Question 5

What are the two classic symptoms of nitrogen deficiency in plants?

Answer 5

(1) stunted growth
(2) general pale yellowing of leaves

Question 6

In addition to readily visible signs of deficiency in the aerial tissues, how else can a nitrogen deficiency be observed using a rhizo-box?

Answer 6

nitrogen-deficient roots are often longer than the better-fed plants

Question 7

The yellowing associated with a nitrogen deficiency is first detectable in what group of leaves?

Answer 7

older leaves first

Question 8

What are three symptoms associated with a deficiency in phosphorus? HINT: two of these are readily visible without soil excavation, the third is not.

Answer 8

(1) stunting in the above-soil portions of the plant
(2) purplish coloration in younger leaves due to anthocyanins
(3) root systems will grow more at the lateral to better scavenge nutrients from the soil, while growth at the apical bud is suppressed

Question 9

What are the roots associated with a phosphorus deficiency referred to as?

Answer 9

cluster roots

Question 10

Potassium deficiency symptoms in plants appear similar to those under drought – what are the two characteristics of potassium deficiency?

Answer 10

(1) wilting appearance (and downward-oriented petioles)
(2) yellowing at the edges when minor, marginal necrosis at leaf edges when severe

Question 11

Why are potassium deficiency symptoms similar to drought symptoms?

Answer 11

potassium helps to maintain turgor pressure in the guard cells – when it leaves those cells, water leaves with it, causing guard cells to become flaccid and close

Question 12

What part of the cell is calcium said to assist in the construction and maintenance of, which causes those cells to be flabby and deteriorate in its absence?

Answer 12

calcium helps to maintain cell walls

Question 13

Soon after calcium enters the plant cell, where is it placed? Why is this done?

Answer 13

calcium is placed in the vacuole of the plant cell to maintain turgidity

Question 14

calcium ions have an antagonist relationship with ions of what other nutrient?

Answer 14

magnesium

Question 15

What is the first sign of a calcium deficiency in a plant?

Answer 15

curling of new leaves if deficiency is moderate, necrotic tips of new leaves if deficiency is severe

Question 16

What is the symptom of calcium deficiency relevant to the apple industry?

Answer 16

bitter pit

Question 17

What is the symptom of calcium deficiency relevant to the tomato industry?

Answer 17

blossom end rot

Question 18

What are the two notable roles played by magnesium in plant metabolism?

Answer 18

(1) magnesium activates RuBisCO to begin fixing carbon dioxide in photosynthesis
(2) magnesium has a central role in the porphyrin ring of the chlorophyll pigment

Question 19

What are the two classic symptoms of magnesium deficiency?

Answer 19

(1) interveinal chlorosis and veins which are lighter tinted than those of well-fed plants (bronzing and death of yellow areas when interveinal chlorosis goes too long without correction)
(2) stunting due to reduced rates of photosynthesis

Question 20

Why can some plant leaves appear purple under a magnesium deficiency?

Answer 20

magnesium is a phosphorus carrier, so low magnesium levels can cause a phosphorus deficiency as well

Question 21

What are the two classic symptoms of sulfur deficiency in crops?

Answer 21

(1) generalized yellowing
(2) stunted growth

Question 22

How do sulfur deficiencies differ visually from nitrogen deficiencies?

Answer 22

Because sulfur is an immobile nutrient, it causes the plant to acquire a yellow appearance in both young and old leaves, while the older leaves of plants typically show signs of nitrogen deficiency first

Question 23

What does it mean that sulfur acts as a soil conditioner?

Answer 23

sulfur helps to reduce the sodium content of soils

Question 24

Typically, because soil is required in low volumes, most plants only need about how much sulfur to grow adequately?

Answer 24

10 to 30 pounds of sulfur per acre

Question 25

Sulfur plays an important role in providing flavor to what five crops?

Answer 25

(1) black currants (Ribes nigrum)
(2/3) horseradish/mustard (Brassicaceae)
(4/5) onions/garlic (Alliums)

Question 26

What is the major risk associated with adequate boron nutrition?

Answer 26

boron is required in very small amounts, and toxicities can arise if too much is applied

Question 27

In what form can boron enter the cell via simple diffusion?

Answer 27

boric acid (H3BO3)

Question 28

In what form is boron taken into the cell with an energy-consuming symport mechanism?

Answer 28

borate (H2BO42-)

Question 29

What role does boron play BETWEEN plant cells?

Answer 29

boron can crosslink cells by attaching to cellulose microfibrils in two different cell walls

Question 30

What are the two classic symptoms of boron deficiency in plant cells?

Answer 30

(1) reduced fruit set
(2) malformation in young plant leaves and stems

Question 31

Boron deficiency symptoms can easily be mistaken for a deficiency in what other nutrient?

Answer 31

calcium

Question 32

What is the underlying reason for which boron and calcium deficiencies are similar?

Answer 32

both link components of the membranes between plant cells – boron links cellulose microfibrils, calcium links pectins

Question 33

New additions of boron to the soil can be beneficial in what kinds of soil? Why?

Answer 33

boron reapplications may be useful for sandy soils, due to the propensity for boron to leach

Question 34

What are some of the symptoms associated with a moderate chlorine deficiency?

Answer 34

wilting or curling of the leaves at the margins

Question 35

What are some of the symptoms associated with a severe chlorine deficiency?

Answer 35

chlorosis, bronzing and necrosis of the leaves

Question 36

What are three symptoms associated with a copper deficiency in plants?

Answer 36

(1) new leaves begin to cup
(2) chlorosis and necrosis in localized spots
(3) leaf nodes grow closer together, causing a more squat plant to arise

Question 37

What are the characteristics of interveinal chlorosis in iron-limited plants?

Answer 37

typically in young tissues (blooms and leaves) first, with the chlorosis being very symmetrical

Question 38

How does a manganese deficiency differ from a deficiency in iron?

Answer 38

manganese deficiencies are less symmetrical and more abrupt between the green and yellow areas than seen in iron

Question 39

What is the underlying reason for which plants suffer low-nitrogen symptoms when they are deficient in molybdenum?

Answer 39

molydenum enables plants to metabolize nitrate, so when molydenum is not adequately present, nitrates build up overtime in the leaves and other tissues

Question 40

What can occur if too many nitrates build up in plant leaves due to molybdenum deficiencies?

Answer 40

burning of the leaves at the margins (plants may also experience stunted growth)

Question 41

What special use do legumes have for molybdenum relative to non-legumes?

Answer 41

fixation of atmospheric nitrogen in the root nodules

Question 42

What are the two symptoms of zinc deficiency in crop plants?

Answer 42

(1) whitening of the leaf margins in a mottled manner
(2) stunted overall growth