Which of the following is a component of the middle lamella?

Zinc is associated with

Iron is present in which of the following?

An element involved in the metabolism of urea is:

Mark the statements as true/false by choosing the correct option from the set $(I-IV)$ given below:
$I.$ Magnesium is a constituent of chlorophyll and helps to maintain the ribosome structure.
$II.$ Calcium is needed during the formation of mitotic spindle.
$III.$ Magnesium is essential for the photolysis of water.
$IV.$ Zinc helps in sugar translocation.

Name the minerals responsible for maintaining cation-anion balance in the plant cells.