Enhancing potassium content in leaves and stems improves drought tolerance of eucalyptus clones

Eucalyptus are widely planted in regions with low rainfall, occasioning frequent drought stresses. To alleviate the stress-induced effects on plants growing in these environments, soil fertilization with potassium (K) may affect drought-adaptive plant mechanisms, notably on tropical soils with low K availability. This work aimed to evaluate the K dynamic nutrition in eucalyptus in response to soil-K and -water availabilities, correlating the K-nutritional status with the physiological responses of contrasting eucalyptus clones to drought tolerance. A complete randomized design was used to investigate the effects of three water regimes (well-watered, moderate water deficit, and severe water deficit) and two K soil supplies (sufficient and low K) on growth and physiological responses of two elite eucalyptus clones: VM01 (Eucalyptus urophylla x camaldulensis) and AEC 0144 (E. urophylla). Results depicted that the K-well-nourished E. urophylla x camaldulensis clone under severe water deficit maintained shoot biomass accumulation by upregulating the K-content in leaves and stems, gas exchange, water-use efficiency (WUEI), leaf water potential (psi w), and chlorophyll a fluorescence parameters, compared to E. urophylla clone. Meanwhile, E. urophylla with a severe water deficit showed a decreased of K content in leaves and stem, as well as a reduction in the accumulation of dry mass. Therefore, the K-use efficiency and the apparent electron transport rate through photosystem II were positively correlated in plants grown in low K, indicating the importance of K in maintaining leaf photochemical processes. In conclusion, management strategy should seek to enhance K-nutrition to optimize water-use efficiencies and photosynthesis.

Automated summary

This study evaluated the potassium dynamic nutrition in eucalyptus in response to soil-K and -water availabilities, finding that eucalyptus clones with sufficient potassium were able to maintain biomass accumulation under severe drought conditions compared to those with low potassium levels. The importance of potassium nutrition in maintaining leaf photochemical processes was highlighted, showing positive correlations between potassium use efficiency and electron transport rate through photosystem II in plants grown in low potassium conditions. Management strategies should focus on enhancing potassium nutrition to optimize water-use efficiencies and photosynthesis.