What is the soil uptake form(s) for chlorine?

The correct answer is the chloride ion, which is the primary form of chlorine that plants can uptake from the soil. Chlorine, as an essential micronutrient for plants, is most commonly found in the soil in the form of chloride, which is highly soluble. This solubility allows it to be easily absorbed by plant roots during their physiological processes.

Chloride plays a vital role in plant functions such as photosynthesis since it is involved in the formation of oxygen during the light-dependent reactions. Additionally, chloride can influence plant water regulation and stomatal activity, which are critical for maintaining plant health and optimizing growth.

Other forms of chlorine, such as chlorate ions, are not typically available in significant amounts or in a form that plants can readily absorb. Boric acid is not related to chlorine and does not contribute to its uptake, while nitrate ions pertain specifically to nitrogen and do not play a role in the uptake of chlorine. Thus, the chloride ion is the recognized and significant form through which plants access and utilize chlorine from the soil.