The smooth muscle cells of both the afferent and efferent arterioles are swollen and contain dark granules. These cells are called Juxtaglomerular cells. These cells secret Renin which convert angiotensinogen into angiotensin.
The epithelial cells of the distal convoluted tubules that comes in contact with the afferent and efferent arterioles are more dense than the other tubular cells and are collectively called muscula densa. The cells of the mascula densa may function as chemoreceptors; feeding information to the juxtaglomerular cells. The juxtaglomerular cells and macula densa together form juxtaglomerular complex.
Macula densa cells are the columnar tubule cells. They are present in the wall of afferent arterioles. The modified fibers of smooth muscles present in the lining of the afferent arteriole are called juxtaglomerular cells.
The juxtaglomerular cells and macula densa cells together make the juxtaglomerular apparatus, also called juxtaglomerular complex. The function of the juxtaglomerular apparatus is to maintain the blood pressure of kidneys.
Because each subject in an experiment has to have equal conditions to ensure the most accurate results. And water temperature is known to impact plant growth. An experiment using different water temperatures is a terribly inaccurate experiment.
