Potassium Starvation Increases Stomatal Conductance in Olive Trees

Abstract

<jats:p>The effects of potassium (K) status and water availability in the growth medium on growth, water content, water-use efficiency and stomatal conductance was studied in mist-rooted `Chemlali de Sfax' olive (<jats:italic>Olea europaea</jats:italic> L.) cuttings grown in a perlite substrate. Potassium starvation produced dehydration of all parts of the plant, reduced shoot growth and water-use efficiency. By contrast, K starvation enhanced stomatal conductance in well-irrigated plants and, even more, in water-stressed plants. These results suggest that moderate K deficiency in olives may impair the plant's ability to regulate stomatal closure; this may account for the dehydration observed in K-starved plants, particularly in situations of water stress. This result is of great importance for agricultural practices of this crop, because K status, which may not be considered deficient, can cause disorders in olive trees.</jats:p>

K+ starvation inhibits water-stress-induced stomatal closure

“…For all treatments, values are means of four replications7standard error. (Arquero et al, 2006). This would suggest that this physiological disorder is widespread among plants, and may be the chief cause of tissue dehydration in many rainfed crops with low potassium content.…”

“…However, in some of these studies, the potassium deficiency was extreme (Hsiao and Läuchli, 1986). In contrast, other authors suggest that potassium deficiency favours stomatal opening and transpiration in wheat and peas (Brag, 1972), sugar cane (Sudama et al, 1998) and, more recently, in the olive cultivar 'Chemlali de Sfax' (Arquero et al, 2006). It is not yet clear why potassium-deficient plants are more susceptible to dehydration.…”

Functioning of potassium and magnesium in photosynthesis, photosynthate translocation and photoprotection

“…Some reports indicate that under combined K deficiency and water‐limitation, stomatal control may be lost in perlite‐grown sunflower and olive plants, resulting in an inhibition of drought‐induced stomatal closure (Fournier et al , Arquero et al , Benlloch‐González et al , ). In accordance with the general concept, the authors do not attribute their results to a loss of osmotic stomatal control, but to an inhibition of the ABA signaling pathway by excessive ethylene production in the leaves.…”

The role of nutrients in drought‐induced tree mortality and recovery

“…Very low nutrient availability and thus the lack of nutrient reserves impairs the plant's ability to sustain drought stress. Potassium deficiency for example is known to have detrimental effects on growth and survival under drought (Arquero et al ., ; Sardans & Peñuelas, ). However, when a nutrient threshold is exceeded, higher nutrient availability predisposes plants to drought‐induced mortality due to morphological and physiological traits that are adaptive towards high nutrient supply but maladaptive for drought survival.…”

“…Conditions of high (or low) nutrient availability can each have positive and negative impacts on the likelihood of forest survival during drought (e.g. Arquero et al, 2006;Coomes et al, 2007;Dziedek et al, 2016). The legacy of high vs low nutrient supply on the long-term, that is, before the direct impact of a drought event, will affect the predisposition of plants to drought.…”