Effects of Elevated [CO2] and Nitrogen Nutrition on Cytokinins in the Xylem Sap and Leaves of Cotton

Abstract

We measured the level of xylem-derived cytokinins (CKs) entering a cotton leaf, and the CK levels in the same leaf, thus enabling xylem sap and foliar CKs to be compared concurrently. Although zeatin was the dominant CK in xylem sap, zeatin, dihydrozeatin, and N 6 -(2-isopentenyl) adenine were present in approximately equimolar levels in leaves. Elevated [CO 2 ] (EC) has an effect on the levels of cytokinins in sap and leaf tissues. This effect was modulated by the two levels of root nitrogen nutrition (2 and 12 mm nitrate). Growth enhancement (70%) in EC over plants in ambient [CO 2 ] (AC) was observed for both nitrogen nutrition treatments. Low-nitrogen leaves growing in EC exhibited photosynthetic acclimation, whereas there was no sign of photosynthetic acclimation in high-nitrogen grown leaves. Under these prevailing conditions, xylem sap and leaf tissues were obtained for CK analysis. Higher nitrogen nutrition increased the delivery per unit leaf area of CKs to the leaf at AC. EC caused a greater increase in CK delivery to the leaf at low nitrogen conditions (106%) than at high nitrogen conditions (17%). EC induced a significant increase in CK content in low-nitrogen leaves, whereas CK content in leaf tissues was similar for high-nitrogen leaves growing in AC and EC.

Control of axillary bud initiation and shoot architecture in Arabidopsis through the SUPERSHOOT gene

“…For the analysis, we used a simplified method for quantifying cytokinins in potentially active forms. Cytokinin ribosides and nucleotides were converted to bases during the process of anhydrous methanolysis, whereas the O-, 7-, and 9-glucoside linkages were not cleaved appreciably Yong et al 2000). Thus, Z, DZ, iP, OGZ, and OGDZ levels presented in this paper refer to the total content of each compound (base) in free, riboside and nucleotide forms.…”

“…This procedure (Chaudhury et al 1993;Wang et al 1995) converts 9-ribosides and nucleotides to bases, whereas O-, 7-, and 9-glucoside linkages are not cleaved appreciably. After three-step column purification (Chaudhury et al 1993), the bases (free plus bound and glucosides) were further purified by HPLC for quantification by scintillation proximity immunoassay Yong et al 2000). Cytokinin bases (Z, DZ, and iP) and Z-9-glucoside were measured directly, but the O-glucosides were first hydrolyzed to bases with ␤-glucosidase (Yong et al 2000).…”

Foliar chemical composition of two oak species grown in a free-air enrichment system with elevated O₃ and CO₂

“…Fangmeier et al, 2002;Thomas et al, 2006), what we found in this study ( Table 2) is in consistence with Wang et al (2015) where leaf K was not clearly different at eO 3 and eCO 2 from that grown under ambient. It was possibly because the decreased photosynthetic rate (Kitao et al, 2015) was somehow offset by the enhanced phytohormones induced by eO 3 or eCO 2 (Yong et al, 2000;Winwood et al, 2007;Matyssek et al, 2012), thereby regulating the foliar K independent with the specific gas treatments. Moreover, the high leaf K in August, both the 1 st and 2 nd flush, was likely connected with remobilisable stored water or with succulence so that K may be accumulated in vacuoles (Von Willert et al, 1992;Cornelissen et al, 1997).…”

18O Spatial Patterns of Vein Xylem Water, Leaf Water, and Dry Matter in Cotton Leaves

“…For sap collection with minimal perturbation, xylem water of an intact leaf was sampled concurrently from primary and secondary veins using a root pressure chamber (Yong et al, 2000). While the whole root system of the plant was enclosed and pressurized in the chamber, a light incision was made on the leaf vein with a sharp razor blade.…”