In summary, our results show that Ca deficiency enhanced Cd toxicity in rice seedlings. Of particular interest is the finding that Ca is required for the expression of rice hsp genes and HS-induced tolerance to Cd in rice seedlings. To our knowledge, no corresponding studies on the effect of Ca deficiency on subsequent Cd stress in plants have been previously published. It appears that stress combination could have a significant impact on agricultural production. To develop sustainable practices, enhancing our knowledge of the molecular, physiological, and metabolic responses of plants to a combination of nutrient deficiency and Cd stress is thus required.