You can make a very effective "whitewash" (or sunscreen) for your body, and for your plants too, from ordinary clay mixed with water. You can find clay almost everywhere on earth, especially in creek beds.
Let's say your car breaks down in the desert and you have to wander for days trying to get back to civilization. Find an arroyo and go deep down in the canyon to where the water is, and dig down in the moist or wet soil and you're sure to find some "mud" (clay). Now you can apply it to your skin to avoid severe (often life-threatening) sunburn. This is what elephants do when the roll around in the mud, applying sunscreen to themselves.
Same method was formerly used, especially in large acreages in California, when transplanting tomato plants to the fields. The plants were dipped in "mud" and they survived the intense light and heat with this coating on them, which naturally fell off in a few days as the plants grew. I've done this myself on several occasions, transplanting tomato plants from a shaded greenhouse to the intense sunlight of the garden.
YouTube title:
DIY Sun Block for Plants
[ NOTES: chalk / hydrated lime / clay will all work the same, and I applied mine to plants already in the ground with a sprayer like that too ]