Abstract
Potassium (K) is generally considered as being closely linked to plant water dynamics. Consequently, reinforcing K nutrition, which theoretically favors root growth and specific surface, extends leaf lifespan, and regulates stomatal functioning, is often used to tackle water stress. We designed a greenhouse pot-scale device to test these interactions on corn (Zea mays L.), and to analyze their links to plant transpiration. Three levels of K nutrition were combined with two water-supply treatments. Shoot and root development and growth were continuously measured during a 60-day-long experiment. Individual plant transpiration was measured by weighing pots and by calculating water mass balances. The results showed that, although K deficiency symptoms resembled those caused by water shortage, there was no advantage to over-fertilizing water-stressed plants. K failed to decrease either the transpiration per unit leaf surface or to improve water use efficiency. The link between K nutrition and plant transpiration appears solely attributable to the effect of K on leaf area. We conclude that K over-fertilization could ultimately jeopardize crops by enhancing early-stage water transpiration to the detriment of later developmental stages.
Highlights
Corn (Zea mays L.) is a crop that is very sensitive to water stress [1,2], which often makes irrigation necessary in most growing areas [3], such as in the southwest of France, a major corn production region.In this temperate part of Western Europe, annual rainfall is expected to decrease by the year 2050, coupled with an increase in the frequency and duration of summer droughts and temperature-driven evaporative demand [4,5]
Deficiency and water shortage lead to comparable morphological root and shoot changes, as K shares some physiological functions with water; (2) K over-fertilization partially offsets the deleterious effects of drought; in which case; (3) this type of compensation is partly due to increases in leaf lifespan and in root specific area, together with a better transpiration regulation
The root system was separated by phytomers (P), which consist in a repetition of constructional units represented by successive horizontal circles from which primary roots emerge at the base of the stem
Summary
Corn (Zea mays L.) is a crop that is very sensitive to water stress [1,2], which often makes irrigation necessary in most growing areas [3], such as in the southwest of France, a major corn production region In this temperate part of Western Europe, annual rainfall is expected to decrease by the year 2050, coupled with an increase in the frequency and duration of summer droughts and temperature-driven evaporative demand [4,5]. We hypothesize that: (1) the effects of K deficiency and water shortage lead to comparable morphological root and shoot changes, as K shares some physiological functions with water; (2) K over-fertilization partially offsets the deleterious effects of drought; in which case; (3) this type of compensation is partly due to increases in leaf lifespan and in root specific area, together with a better transpiration regulation
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