Wheat or sheaves show up in a few places in the temple. 

These are small details so, difficult to see in the images.

The original temple site in Jerusalem was built on the site of a threshing floor. "Then Solomon began to build the house of the Lord at Jerusalem in mount Moriah, where the Lord appeared unto David his father, in the place that David had prepared in the threshingfloor of Ornan the Jebusite."

Mount Moriah was the same location where Abraham nearly offered up Isaac for sacrifice, but then he was halted by an angel and offered up the ram instead.

In the days of Abraham, Melchizedek was the king of Salem. 

Over time the Jebusites took possession of the city of Jerusalem.

Then King David conquered that city and made it his capital.

At one time, this outcropping on Mount Moriah was used by Ornan (also known as Araunah), the Jebusite king, as a threshing floor. In ancient cultures the threshing floor was a sacred space used for religious rites when it was not in use for harvesting.

2 Samuel 24 records the events that transferred this property to King David. David sinned in numbering the Israelites and God sent a plague to the children of Israel. The prophet Gad received this instruction for David: "Go up, rear an altar unto the Lord in the threshingfloor of Araunah the Jebusite."

So David goes to buy the property. "And Araunah said, Wherefore is my lord the king come to his servant? And David said, To buy the threshingfloor of thee, to build an altar unto the Lord, that the plague may be stayed from the people. And Araunah said unto David, Let my lord the king take and offer up what seemeth good unto him: behold, here be oxen for burnt sacrifice, and threshing instruments and other instruments of the oxen for wood."

The wording of this next part suggests that both David and Araunah are kings (indeed, the name Araunah is basically a Hittite word for lord), which makes this transfer of property so significant. "All these things did Araunah, as a king, give unto the king."

"And the king said unto Araunah, Nay; but I will surely buy it of thee at a price: neither will I offer burnt offerings unto the Lord my God of that which doth cost me nothing. So David bought the threshingfloor and the oxen for fifty shekels of silver. And David built there an altar unto the Lord, and offered burnt offerings and peace offerings. So the Lord was entreated for the land, and the plague was stayed from Israel." 

The language about buying the property at full price is straight from Abraham. "But if thou wilt give it, I pray thee, hear me: I will give thee money for the field; take it of me, and I will bury my dead there."

So that was how David acquired the threshingfloor on Moriah. He passed it on to Solomon, who built the first temple there.

So, wheat is a symbol connecting the temple with David and, by extension, Abraham. David was the King and Abraham was the Priest. 

This temple symbol is taught in Revelation 1:6 "And hath made us kings and priests unto God and his Father"

Wheat is a symbol of the righteous. This is well known in Jesus' parable of the wheat and tares.

There is a reference fitting for the Celestial Room found in the Doctrine and Covenants: "Therefore, I must gather together my people, according to the parable of the wheat and the tares, that the wheat may be secured in the garners to possess eternal life, and be crowned with celestial glory, when I shall come in the kingdom of my Father to reward every man according as his work shall be"

This probably also applies to the parable of the sower, "But he who received seed on the good ground is he who hears the word and understands it, who indeed bears fruit and produces: some a hundredfold, some sixty, some thirty."

Scriptures also distinguish between wheat and chaff.

A threshing floor reminds us of this prophecy from John the Baptist: "Whose fan is in his hand, and he will thoroughly purge his floor, and gather his wheat into the garner; but he will burn up the chaff with unquenchable fire."

Hosea called idol worshippers to repentance with the image of chaff: "Therefore they shall be as the morning cloud, and as the early dew that passeth away, as the chaff that is driven with the whirlwind out of the floor, and as the smoke out of the chimney. Yet I am the Lord thy God from the land of Egypt, and thou shalt know no god but me: for there is no saviour beside me."

This was probably what the Savior was alluding to when he told Peter, "behold, Satan hath desired to have you, that he may sift you as wheat."

Wheat is an important symbol of labor and harvest. This verse is familiar: "For behold the field is white already to harvest; and lo, he that thrusteth in his sickle with his might, the same layeth up in store that he perisheth not, but bringeth salvation to his soul" D&C 4:4

I particularly like this one, "Therefore, thrust in your sickle with all your soul, and your sins are forgiven you, and you shall be laden with sheaves upon your back, for the laborer is worthy of his hire. Wherefore, your family shall live." D&C 31:5 (Big thanks to all my family who have thrust in their sickles.)

We think of lambs and animal sacrifices at the ancient temples, but let us not forget the offerings of grain as firstfruits: "When ye be come into the land which I give unto you, and shall reap the harvest thereof, then ye shall bring a sheaf of the firstfruits of your harvest unto the priest: And he shall wave the sheaf before the Lord, to be accepted for you"

Maybe we should remember this Proverb: "Be not wise in thine own eyes: fear the Lord, and depart from evil. It shall be health to thy navel, and marrow to thy bones. Honour the Lord with thy substance, and with the firstfruits of all thine increase: So shall thy barns be filled with plenty, and thy presses shall burst out with new wine." Proverbs 3:7-10

Jesus was the firstfruits of the resurrection: "But now is Christ risen from the dead, and become the firstfruits of them that slept."

Firstfruits has also been applied to Jesus' followers: "These are they which follow the Lamb whithersoever he goeth. These were redeemed from among men, being the firstfruits unto God and to the Lamb."

Wheat is a symbol of Jesus Christ, Himself, with His death, burial and resurrection. "Verily, verily, I say unto you, Except a corn of wheat fall into the ground and die, it bideth alone: but if it die, it bringeth forth much fruit." This is also a symbol of our new life, born again as disciples of Jesus.

It is just a short jump from wheat to bread. Jesus is the Bread of Life. "I am the living bread which came down from heaven: if any man eat of this bread, he shall live for ever: and the bread that I will give is my flesh, which I will give for the life of the world."

So, in summary, wheat points us back to the origin story of the Jerusalem temple and connects to King David and Patriarch Abraham.

Wheat is a symbol of the righteous.

Wheat is a symbol of the work we do for the Lord.

Wheat is a kind of sacrifice that we offer to God- the firstfruits.

Wheat is a symbol of the Lord, Himself.

I'm pretty sure the Word of Wisdom includes a symbolic element when it states, "wheat for man."