chlorophyll-a and Potassium-Deficiency

The interaction between low sink demand and potassium (K) deficiency in leaf photosynthesis was not intensively investigated, therefore this interaction was investigated in winter oilseed rape (Brassica napus L.). Plants subjected to sufficient (+K) or insufficient (-K) K supply treatments were maintained or removed their flowers and pods; these conditions were defined as high sink demand (HS) or low sink demand (LS), respectively. The low sink demand induced a lower photosynthetic rate (P

Topics: Brassica napus; Carbohydrate Metabolism; Carbon Dioxide; Chlorophyll; Feedback, Physiological; Flowers; Hydrogen-Ion Concentration; Photosynthesis; Plant Leaves; Potassium; Potassium Deficiency

Although silicon (Si) has been widely reported to alleviate plant nutrient deficiency, the alleviating effect of Si on potassium (K) deficiency and its underlying mechanism are poorly understood. Here, we examined whether Si-regulated putrescine (Put) metabolisms are involved in Si-alleviated K deficiency.. Sorghum seedlings were grown in K deficiency solution with and without Si for 15 d. The influence of K deficiency and Si on leaf chlorosis symptoms, K(+) concentration, polyamine (PA) levels, amine oxidase activities, the transcription of Put synthesis genes, antioxidant enzyme activities and H2O2 accumulation were measured.. Under K-sufficient conditions, plant growth was not affected by Si application. Si application significantly alleviated the growth inhibition induced by K-deficient stress, however. K deficiency induced leaf chlorosis and reduction in several leaf chlorosis-related metrics, including photosynthesis, efficiency of photosystem II photochemistry, chlorophyll content and chlorophyll a/b ratio; all of these changes were moderated by Si application. Si application did not influence the K(+) concentration in leaves under K-sufficient or K-deficient conditions. It did, however, decrease the excessive accumulation of Put that was otherwise induced by K deficiency. Simultaneously, Put synthesis gene transcription and activation of amine oxidases were down-regulated by Si application under K-deficient conditions. In addition, Si reduced K-deficiency-enhanced antioxidant enzyme activities and decreased K-deficiency-induced H2O2 accumulation.. These results indicate that Si application could reduce K-deficiency-induced Put accumulation by inhibiting Put synthesis and could decrease H2O2 production via PA oxidation. Decreased H2O2 accumulation contributes to the alleviation of cell death, thereby also alleviating K-deficiency-induced leaf chlorosis and necrosis.

Topics: Antioxidants; Carboxy-Lyases; Chlorophyll; Chlorophyll A; Hydrogen Peroxide; Photosynthesis; Plant Leaves; Plant Proteins; Polyamines; Potassium Deficiency; Putrescine; Seedlings; Silicon; Sorghum

The main aim of this work is to identify how the combined stresses affect the interdependent nitrogen and photosynthetic carbon assimilations in maize. Maize plants were cultivated in Meider's solution. They were subjected to salt stress and potassium deficiency in the K-present Meider's media and K-deficient Meider's media. After 5 weeks, we measured chlorophyll a fluorescence and the activities of several enzymes in metabolic checkpoints coordinating primary nitrogen and carbon assimilation in the leaves of maize. The study showed that the combination of salt stress and potassium-deficient stress more significantly decreased nitrate uptake, plant growth, the activities of nitrate reductase, glutamate dehydrogenase, glutamate synthase, urease, glutamic-pyruvic transaminase, glutamic-oxaloace transaminase, sucrose-phosphate synthase, phosphoenolpyruvate carboxylase, and the synthesis of free amino acids, chlorophyll, and protein than those of each individual stress, respectively. However, the combined stresses significantly increased the accumulation of ammonium and carbohydrate products. The combined stresses also significantly decreased the oxygen evolution, the electron transport, and the efficiency of photochemical energy conversion by photosystem II in maize seedlings. Taken together, a combination of salt stress and potassium-deficient stress impaired the assimilations of both nitrogen and carbon and decreased the photosystem II activity in maize.

Topics: Amino Acids; Carbohydrate Metabolism; Carbon; China; Chlorophyll; Chloroplasts; Mass Spectrometry; Nitrogen; Oxygen; Photosynthesis; Plant Leaves; Plant Proteins; Potassium; Potassium Deficiency; Quaternary Ammonium Compounds; Seedlings; Sodium; Spectrometry, Fluorescence; Zea mays

The mechanisms of photoprotection of photosynthesis and dissipation of excitation energy in rice leaves in response to potassium (K) deficiency were investigated. Net photosynthetic rate and the activity of ribulose-1,5-bisphosphate carboxylase/oxygenase decreased under K deficiency. Compared with the control, non-photochemical quenching of Chl fluorescence increased in K-deficient plant, whereas the efficiency of excitation transfer (F'(v)/F'(m)) and the photochemical quenching coefficient (q(P)) decreased. Thus, thermal dissipation of excitation energy increased as more excess electrons were accumulated in the photosynthetic chain. The electron transport rate through PSII (J(f)) was more sensitive to O2 concentration, and the fraction of electron transport rate required to sustain CO2 assimilation and photorespiration (J(g)/J(f)) was significantly decreased under K deficiency compared with the control. Furthermore, the alternative electron transport (J(a)/J(f)) was increased, indicating that a considerable amount of electrons had been transported to O2 during the water-water cycle in the K-deficient leaves. Although the fraction of electron transport to photorespiration (J(o)/J(f)) was also increased in the K-deficient leaves, it was less sensitive than that of the water-water cycle. With the generation of reactive oxygen species level, the activities of superoxide dismutase and ascorbate peroxidase, two of the key enzymes involved in scavenging of active oxygen species in the water-water cycle, also increased in K-deficient rice. Therefore, it is likely that a series of photoprotective mechanisms were initiated in rice plants in response to K deficiency and the water-water cycle might be critical for protecting photosynthetic apparatus under K deficiency in rice.

Topics: Chlorophyll; Electron Transport; Kinetics; Oryza; Photosynthesis; Plant Leaves; Potassium; Potassium Deficiency; Ribulose-Bisphosphate Carboxylase; Superoxides; Water