Silicon is proven to enhance drought and heat tolerance in plants.
Silicon is one of most abundant elements in nature, second only to oxygen. It makes up about 1/4 of the Earths crust. It is a naturally occurring element found in soil and works its way up the food chain through the plant and animal kingdoms.
Benefits of Silicon
Run off from soils contains approximately 400 ppm of silicic acid, which is readily absorbed by plants in nature. Plant tissues of soil grown specimens contain approximately 10% silicon [dry weight], which is fairly close to the dry weight of phosphorous and manganese.
It strengthens the cellular walls, improving the plants tissue strength, overall health, vitality and productivity. Silicon enables plants to cope with toxic levels of certain elements such as manganese, iron, phosphorus and aluminium as well as deficiencies in zinc.Silicon increases plants resistance to pests and pathogens. Without silicon - plant life as we know it could not exist.
It is pretty well established that silicon is advantageous to drought tolerance in plants, a number of studies all support this.  Plants absorb Silicon as monosilicic acids that are naturally present in soil. Supplementing garden soil with silicic acid will serve to strengthen plants drought tolerance.
There are a number of ways to supplement the silicon your garden will receive via nature. Most common is via fertilzers that contain silicon dioxide and or silica.
Another method is via foliar sprays applied to the foliage periodically. Foliar sprays of soluble silicon are effective for control of aphids and other sucking insects on many plants, they can also enhance the drought tolerance of the plants.
Diatomaceous earth is comprised of large amounts of amorphous silicon dioxide and sometimes low levels crystalline silicon dioxide. It is a natural substance used for pest suppression and is also useful if amended modestly into the soil in that it adds silicon for absorption by the plants.