By studying their forms, could you guess the specific function of any of these objects?

I couldn't. I found them all on a website called Monotaro, a Japanese hardware retailer, in what appears to be their gardening and agriculture section. Some of them are designed to make harvesting easier, by providing a collection surface that can be wheeled harmlessly over a row of crops. Others are designed to solve this problem:

Standing up while working crops or plants at ground level is, of course, murder on the back. The bulk of these objects allows you to do the job on your ass, while providing a simple means of moving down the row:

(If the hunched-over seated position still doesn't look comfortable to you, consider that Japan is one of the many countries in the world where people are entirely comfortable squatting.)

A rough machine translation of the product pages explains their functions:

Aina No. Strawberry harvesting wagon 5-stage type

Obviously in the harvesting category. I couldn't figure out why the top tray is level and the lower trays are slanted, and needed the translation to understand.

"Since it is divided into each stage, you can put it in and out with confidence.
Since the top row is tilted toward you, you can put strawberries in a stable manner from the front. In addition, the lower four steps are inclined forward, so the harvested strawberries are stable."

Aluminum worker

This is for moving down the row while harvesting or planting. It comes in different configurations (hence the three photos) and is designed to carry a lot of weight.

"An indispensable tool for planting seedlings in harvesting work. Made of aluminum, it is light and has excellent operability and durability. For harvesting and transporting heavy items. The height and width of the table can be changed depending on the application."

Horizontal assistant

You load this thing up with a roll of plastic film, and use it to stretch the plastic into a tunnel over the half-hoops you've laid down, creating a mini-greenhouse over the crops. I'd seen the crop tunnels before, but never saw how they applied the plastic.

"You can extend and wind the film while moving it with a dolly without having to lift and carry the film for tunnels and mulch. Since it has an anti-reverse device (ratchet), the film can be wound while aligning even by one person."

Non-key

Two variants, both with wide tires for stability. The second one appears to be more of a "deluxe" model in that the seat is height-adjustable, and it's got that basket for holding tools.

"Because the seat is wide, you won't get tired even if you work for a long time! The comfortable seat that considers the ride quality improves work efficiency. There are various ways to use it depending on the idea. Great for all kinds of work!! Rust resistant and keeps a beautiful luster forever."

RSA-400 passenger work platform high type

Similar idea as above, but for working taller crops. Slightly better UX as it hasa swivel seat and a handle for manipulating the thing into place.

"The RSA-400 has a slightly higher seating surface, making it ideal for work above the ground. The tires are as large as 12 inches and run smoothly, reducing the strain on your lower back. In addition, the figure eight tire structure is excellent in stability. The chair finished in a special shape has good cushioning and does not get tired even if you work for a long time. In addition, since the chair rotates, you can work in a comfortable posture in either the front, back, left, or right direction. Comes with a handle that is convenient for moving."

RSA-640L passenger work platform low type

This one still has a swivel seat, but puts you in a lower and sideways position compared to the model directly above. It's also got a longer wheelbase, but I'm not sure if that's a desirable feature or simply a function of making room for both the wheels and the seat.

"The RSA-640L has a low seating surface, making it ideal for sideways work near the ground. The tires are as large as 12 inches and run smoothly, reducing the strain on your lower back. In addition, the figure eight tire structure is excellent in stability. The chair finished in a special shape has good cushioning and does not get tired even if you work for a long time. In addition, since the chair rotates, you can work in a comfortable posture in either the left or right direction. Comes with a handle that is convenient for correcting the direction."

Rakuemon High-rise strawberry trolley

The most bicycle-like one yet, at least in appearance. This one's got a height-adjustable swivel seat, cambered wheels for stability, and a handy tray holder.

"The chair slides up and down and rotates left and right, so you can work in a comfortable posture while sitting."

Easy turn chair

Certainly the most basic of the bunch; it looks like a child's toy. Interestingly, the seat is a Lazy Susan.

"Work and movement can be done easily. Long hours of work are also easy. Ideal for farm work, weeding, etc. The seat rotates 360 degrees."

Garden Chair Pro

This one's got beefy pneumatic tires, for rolling through the rough stuff. The lower handle's for scooching around while seated, and the higher handle's for carrying it.

"Make gardening work more comfortable. It is a durable tube tire specification. You can move while sitting and work easily. Comes with a comfortable cushion. Comes with a handle that is convenient to carry."

If it's not clear from the photos, most of these objects are absolutely diminutive. You can get an idea of the scale by scanning through this video:

Enter a caption (optional)

Even before I knew what these things did, I instantly liked all of them, because there is a real purity to their design. These are obviously tools, and appear to be built as economically as possible, absent any extraneous parts, decoration or flair. And the variety of solutions reminds me a lot of ID school assignments on presentation day.