Changes in leaf growth, net photosynthetic rate (PN), incorporation pattern of photosynthetically fixed 14CO2 in leaves 1-4 from top, roots, and rhizome, and in essential oil and curcumin contents were studied in turmeric plants grown in nutrient solution at boron (B) concentrations of 0 and 0.5 g m-3. B deficiency resulted in decrease in leaf area, fresh and dry mass, chlorophyll (Chl) content, and PN and total 14CO2 incorporated at all leaf positions, the maximum effect being in young growing leaves. The incorporation of 14CO2 declined with leaf position being maximal in the youngest leaf. B deficiency resulted in reduced accumulation of sugars, amino acids, and organic acids at all leaf positions. Translocation of the metabolites towards rhizome and roots decreased. In rhizome, the amount of amino acids increased but content of organic acids did not show any change, whereas in roots there was decrease in contents of these metabolites as a result of B deficiency. Photoassimilate partitioning to essential oil in leaf and to curcumin in rhizome decreased. Although the curcumin content of rhizome increased due to B deficiency, the overall rhizome yield and curcumin yield decreased. The influence of B deficiency on leaf area, fresh and dry masses, CO2 exchange rate, oil content, and rhizome and curcumin yields can be ascribed to reduced photosynthate formation and translocation. and Deeksha Dixit, N. K. Srivastava, S. Sharma.
At the grain-filling stage, net photosynthetic rate (PN), stomatal conductance (gs), and ribulose-1,5-bisphosphate carboxylation efficiency (CE) were correlated in order to find the determinant of photosynthetic capacity in rice leaves. For a flag leaf, PN in leaf middle region was higher than in its upper region, and leaf basal region had the lowest PN value. The differences in gs and CE were similar. PN, gs, and CE gradually declined from upper to basal leaves, showing a leaf position gradient. The correlation coefficient between PN and CE was much higher than that between PN and gs in both cases, and PN was negatively correlated with intercellular CO2 concentration (Ci). Hence the carboxylation activity or activated amount of ribulose-1,5-bisphosphate carboxylase/oxygenase rather than gs was the determinant of the photosynthetic capacity in rice leaves. In addition, in flag leaves of different tillers PN was positively correlated with gs, but negatively correlated with Ci. Thus gs is not the determinant of the photosynthetic capacity in rice leaves. and D.-Y. Zhang ... [et al.].
Developmental changes of plant in the regulation of photosynthate distribution of leaves were studied in hydroponically cultivated rice by the 14CO2 tracer technique and analysis of the activity of the regulatory enzymes, sucrose phosphate synthase (SPS), phosphoenolpyruvate carboxylase (PEPC), and pyruvate kinase (PK). The distribution of primary photosynthates into sugars, amino acids, organic acids, sugar phosphates, proteins, and polysaccharides was determined by column chromatography. The relative primary photosynthate distribution to the sugar phosphate fraction was significantly larger in the 5th leaf than in the 6th one. Correspondingly, the Vmax of PEPC was significantly higher in the 5th than in the 6th leaf, while no significant differences between leaves were detected in the other enzymes. As a consequence, the ratio of the Vmax of SPS and PEPC was lower in the 5th than in the 6th leaf. As the 5th leaf develops before panicle initiation in rice, it predominantly supports vegetative growth, while the 6th leaf develops after panicle initiation and thus contributes mainly to reproductive growth. We conclude that the physiological properties of each leaf are regulated developmentally. When the 6th leaf became fully expanded (corresponding to the panicle initiation stage of plant), the distribution pattern of 14C was transiently changed in the 5th leaf, indicating that individual organs that are mainly involved in vegetative development are affected to some extent by the whole-plant-level physiological transformation that occurs at the transition from the vegetative to the reproductive stage. and T. Shinano ... [et al.].
Changes in leaf growth, photosynthetic efficiency, and incorporation pattern of photosynthetically fixed 14CO2 in leaves 1 and 2 from plant apex, in roots, and rhizome induced in Curcuma by growing in a solution culture at Fe concentration of 0 and 5.6 g m-3 were studied. 14C was incorporated into primary metabolites (sugars, amino acids, and organic acids) and secondary metabolites (essential oil and curcumin). Fe deficiency resulted in a decrease in leaf area, its fresh and dry mass, chlorophyll (Chl) content, and CO2 exchange rate at all leaf positions. The rate of 14CO2 fixation declined with leaf position, maximum being in the youngest leaf. Fe deficiency resulted in higher accumulation of sugars, amino acids, and organic acids in leaves at both positions. This is due to poor translocation of metabolites. Roots and rhizomes of Fe-deficient plants had lower concentrations of total photosynthate, sugars, and amino acids whereas organic acid concentration was higher in rhizomes. 14CO2 incorporation in essential oil was lower in the youngest leaf, as well as incorporation in curcumin content in rhizome. Fe deficiency influenced leaf area, its fresh and dry masses, CO2 exchange rate, and oil and curcumin accumulation by affecting translocation of assimilated photosynthates. and Deeksha Dixit, N. K. Srivastava.
Leaf-specific Farquhar-von Caemmerer-Berry (FvCB) model was fitted to characterize the vertical profile of photosynthetic CO2 response within rice canopy. Leaf-position-specific and canopy average FvCB models were fitted to study a suitable leaf representing photosynthetic parameters at the canopy scale. The results showed that leaf photosynthesis was limited by Rubisco activity or ribulose-1,5-bisphosphate regeneration under field conditions. The maximum rate of carboxylation, maximum rate of electron transport, rate of triose phosphates utilization, and light respiration rate in the FvCB model reached the highest values for the top second leaf and then decreased, while the mesophyll diffusion conductance kept decreased in downward leaves. The integrated photosynthetic CO2-response curves for the top fourth and fifth leaves were appropriate for estimating parameters in the FvCB model at the canopy scale.