Substrates and Importance of Water

Question 1

Osmosis creates the turgor pressure in plant cell’s that help the cell maintain its shape, and expand its size. TRUE OR FALSE

Answer 1

True

Question 2

Please select all that apply. Water is important to plant growth because…

Answer 2

-it carries the dissolved nutrients that the plant needs for growth and development
-it is needed for the process of respiration
-it helps plant cells keep their shape and their size.

Question 3

Compost is commonly added to substrates for what reason?

Answer 3

providing a starter change of nutrients to the media

Question 4

Please select all that apply. Which of the following statements about Rockwool are true?

Answer 4

-It has 0 cation exchange capacity

Question 5

Dolomitic Lime is commonly added to substrates for what reason?

Answer 5

To raise pH and provide some pH buffering capacity

Question 6

The ratio of the total volume of water that is held in a saturated substrate after all the excess water has drained, to the substrate’s total volume is called

Answer 6

Water Holding Capacity

Question 7

Engineered wood fibers are being used more frequently in growing mixes becuase…

Answer 7

-it generally costs less than perlite and coir
-it is a renewable resource unlike peat

Question 8

Please select all that apply. Which of the following statements about Sphagnum Peat Moss are true?

Answer 8

-requires a wetting agent
-is susceptible to compaction over time
-needs dolomitic limestone added because naturally low pH

Question 9

The ratio of the dry weight of the solid particles in a substrate to its total volume is called

Answer 9

Bulk density

Question 10

The optimal substrate pH for maximum nutrient availability is 6.2 - 7.3. TRUE OR FALSE

Answer 10

True

Question 11

Vermiculite is often incorporated into growing mixes because it will greatly increase the air porosity and drainage of the mix. TRUE OR FALSE

Answer 11

False
Adding vermiculite to to a mix increases the growing medias water holding capacity.

Question 12

Perlite will often be used as a top coat in plug trays. TRUE OR FALSE

Answer 12

False
Perlite typically added to increase air porosity and reduces the water holding capacity.

Question 13

Mycorrhizal fungi are commonly added to substrates for what reason?

Answer 13

Added to improve the plant’s ability to uptake nutrients

Question 14

The ratio of the total volume of air space in a saturated substrate (after the excess water has drained) to its total volume is called

Answer 14

Water holding capacity

Question 15

Active transport uses energy to move solutes across membranes that they are not permeable to, or against a natural concentration gradient. TRUE OR FALSE

Answer 15

True (**)

Question 16

It is important to maintain the pH of a substrate in the optimal range to limit the amount of nutrients that plant will take up at one time. TRUE OR FALSE

Answer 16

False
Outside of the optimal range the plant will experience deficiency, pH levels affect that plants ability to uptake nutrients.

Question 17

Substrates used in the greenhouse are also called growing media. TRUE OR FALSE

Answer 17

True

Question 18

Cation Exchange Capacity, or CEC, is a measure the the substrates ability to hold water. TRUE OR FALSE.

Answer 18

False.
Cation Exchange is the soils ability to hold positively charged nutrient ions. A higher cation exchange rate the more nutrients available to plants.

Question 19

The ratio of the total volume of pore space in a substrate to its total volume is called

Answer 19

Total Porosity

Question 20

Biological organisms like Trichoderma spp. are commonly added to substrates for what reason?

Answer 20

to provide protection against soil borne pathogens like Pythium, Rhizoctonia and Fusarium spp.

Question 21

Which of the following statements about osmosis is correct.

Answer 21

Osmosis involves the movement of water from areas of low concentration to high concentration.

Question 22

The movement of water from the roots to the shoots of plants occurs because…

Answer 22

Osmosis draws water into the roots and transpiration evaporates water from the leaves.

Question 23

Please select all that apply. Which of the following statements about Coconut Coir are true?

Answer 23

-It needs to be washed and buffered with Calcium Nitrate prior to planting

Question 24

Leaching Fraction is…

Answer 24

the amount of extra irrigation water that must be applied above the amount required by the crop in order to maintain an acceptable root zone salinity