ABSTRACT
The location of the phloem within a plant, and its vulnerability to disruption, make it a difficult tissue to study and therefore non-invasive studies of phloem functionality are important. Here we compare, phloem transport, measured non-invasively, in wild type Arabidopsis thaliana, and transposon-insertion mutants for AtSUC1 or AtSUC2, giving in vivo information on the importance of these sucrose transporters for phloem transport. The suc2 mutant showed an increase in both phloem leakage and transport time, consistent with reduced sucrose uptake into both transport and collection phloem. The results are consistent with the AtSUC2 transporter being important for retrieval of leaked sucrose in the transport phloem of Arabidopsis. There was no difference in phloem transport properties between the wild type and the suc1 mutants, implying that the AtSUC1 transporter does not play a significant role within the transport phloem of Arabidopsis under the conditions of our study.
Subject(s)
Arabidopsis/metabolism , Gene Expression Regulation, Plant/genetics , Membrane Transport Proteins/metabolism , Phloem/metabolism , Plant Proteins/metabolism , Sucrose/metabolism , Arabidopsis/genetics , Biological Transport , Carbon/metabolism , Carbon Radioisotopes , Gene Knockout Techniques , Membrane Transport Proteins/genetics , Mutagenesis, Insertional , Plant Proteins/geneticsABSTRACT
Positron emitters such as (11)C, (13)N and (18)F and their labelled compounds are widely used in clinical diagnosis and animal studies, but can also be used to study metabolic and physiological functions in plants dynamically and in vivo. A very particular tracer molecule is (11)CO(2) since it can be applied to a leaf as a gas. We have developed a Plant Tomographic Imaging System (PlanTIS), a high-resolution PET scanner for plant studies. Detectors, front-end electronics and data acquisition architecture of the scanner are based on the ClearPET system. The detectors consist of LSO and LuYAP crystals in phoswich configuration which are coupled to position-sensitive photomultiplier tubes. Signals are continuously sampled by free running ADCs, and data are stored in a list mode format. The detectors are arranged in a horizontal plane to allow the plants to be measured in the natural upright position. Two groups of four detector modules stand face-to-face and rotate around the field-of-view. This special system geometry requires dedicated image reconstruction and normalization procedures. We present the initial performance of the detector system and first phantom and plant measurements.
Subject(s)
Plants , Positron-Emission Tomography/instrumentation , Carbon Dioxide , Carbon Radioisotopes , Equipment Design , Hordeum , Image Processing, Computer-Assisted , Imaging, Three-Dimensional/instrumentation , Imaging, Three-Dimensional/methods , Phantoms, Imaging , Plant Roots , Positron-Emission Tomography/methods , Rotation , Time FactorsABSTRACT
A midribless (mbl) mutant of Panicum maximum Jacq. induced by ethylmethanesulfonate treatment was characterized with respect to morphological and physiological features. The absence of the midrib was accompanied by a reduction of the large veins in the leaf lamina from 25% of total veins found in the wildtype to 13%. The florets of the mutant had no carpel but one or two extra stamens were observed. Similar phenotypic changes have been described for an ovaryless (ovl) mutant of barley. This supports the suggestion that a common morphogenetic determinant in wildtype plants induces both the development of the main midrib in leaves and the carpel in florets. Photosynthetic rate, CO2-compensation point and export of photosynthates, however, were similar in leaves of mutant and wild type plants.
