Shoot and root growth of hydroponic maize (Zea mays L.) as influenced by K deficiency

Abstract

Potassium (K) has major biophysical and biochemical functions in plant physiology. However, plant responses to K deficiency at the whole plant level are not always clearly related to these wellknown functions of K at the cellular level. The objective of this study was to investigate the morphological response of maize to increasing K deficiency and test to what extent this morphological response can be interpreted in the light of the simple model proposed by Leigh and Wyn Jones, suggesting that biophysical functions are affected first. Maize was grown in a greenhouse under hydroponic conditions. For half of the plants, K was removed from the nutrient solution from the 4th visible leaf stage. The K content in the starved plants dropped from 100 to 30 mM, and was not fully compensated by an increase in other cations. Leaf elongation rates were reduced on K-deprived plants, whereas axile root elongation rates were slightly increased between 45°C days and 75°C days after starvation, and reduced thereafter. During the first part of the starvation period, i.e. under moderate K deficiency (K concentration above 40 mM), all measured variables suggest that the whole plant response may be interpreted as the consequence of the reduced leaf growth, probably due to insufficient turgor pressure or cell-wall extensibility. This general pattern of response is in agreement with the model of Leigh and Wyn Jones. However, during the second part of the starvation period, i.e. under more severe K deficiency (K concentration below 40 mM), malfunction of additional physiological processes (mostly related to biochemical functions like photosynthetic processes) must be considered to explain the plant morphological response.

Root mass for oilseed and pulse crops: Growth and distribution in the soil profile

“…There are considerable root data related to cereal crops (Bolinder et al 1997;Niu et al 2004;Caires et al 2008;Jordan-Meille and Pellerin 2008), especially some of the studies conducted in the 1970s and 1980s (Wellbank et al 1974;Campbell et al 1977;Gregory et al 1978;Buyanovsky and Wagner 1986). However, very limited literature exists in which extensive measurements of roots have been taken for oilseed and pulse crops under field conditions.…”

“…However, crop roots are very difficult to measure, and thus research on roots has lagged behind that on above-ground (AG) biomass. In the literature, there are many studies documenting root characteristics of field crops, but the vast majority of these studies have considered cereals (Campbell et al 1977;Bolinder et al 1997;Niu et al 2004;Caires et al 2008;Jordan-Meille and Pellerin 2008). To date, there are no detailed studies reporting root growth and biomass distribution profile in soil for oilseeds or pulses.…”

Leaf photosynthetic capacity is regulated by the interaction of nitrogen and potassium through coordination of CO2 diffusion and carboxylation

“…In contrast to N, K cannot function as a component of key enzymes or proteins involved in photosynthesis. As a dominant osmolyte, increasing the K + concentration in guard cells improved cell turgor, which promotes water absorption by these cells and open stomata (Jordan‐Meille and Pellerin , Ahmad and Maathuis ). Stomatal morphology is altered under long‐term K deficiency, and the total stomatal pore area decreases, resulting in lower stomatal conductance (Battie‐Laclau et al ).…”

Effect of carbon assimilation on dry weight production and partitioning during vegetative growth

“…DW reduction may be the consequence of a reduction in photosynthesis per leaf unit area (Bednarz and Oosterhuis 1999;Zhao et al 2001;Jordan-Meille and Pellerin 2008;Pettigrew 2008). Three major causes of a reduction of photosynthesis under K deficiency have been implicated: (i) reduced stomatal and mesophyll conductance (Terry and Ulrich 1973;Longstreth and Nobel 1980;Pervez et al 2004): (ii) a negative feedback on CO 2 assimilation rates induced by the accumulation of soluble sugars Roitsch 1999) which can impact negatively on the activity of the enzyme Rubisco (Farquhar et al 1980); (iii) impaired counterbalancing by K + of H + accumulation during electron transport across the thylakoid membrane (Mengel 1984;Tester and Blatt 1989;Weng et al 2007).…”