A re-evaluation of plastochron index determination in peas — a case for using leaflet length

The plastochron index (PI) is a measure of plant growth and can be used to determine growth rate, based upon appearance of successive leaves on the axis of the plant. PI should under ideal growth conditions be a regular event and should be predictable with a relatively small error of a few hours. PI has been variously calculated in peas, and each method reported has had with it a number of problems that do not allow for reasonable prediction of PI. Internode length varies greatly and is dependent upon the variety, which may be short- or long-stemmed; thus this parameter is not ideal for determining growth rate or plant age. This paper reports our findings on PI using the average length of the first pair of leaflets on each node. Early leaflet growth in peas occurs exponentially and the early stages of growth of successive pairs of leaflets occur at the same relative growth rate. Given that growth of leaflets during early development can be measured successfully, we propose the use of leaflet growth as a measure of the plastochron index in peas. Our results suggest that plant age is best expressed using the plastochron index, which is a measure of the time interval between the initiations of successive events — in the case of peas, of successive pairs of leaflets

Phenotyping of dark and light adapted barley plants by the fast chlorophyll a fluorescence rise OJIP

Chlorophyll a fluorescence of dark adapted leaves of barley plants (Hordeum vulgare L.) upon exposure to actinic light was measured. We compared the photosynthetic behaviour of ten cultivars of barley plants in the dark and light adapted states. A significant relationship between the light adaptation (S1 to S2 transition) of the photosynthetic Performance Index (lPI/dPI) and the normalised Area (lSm/dSm) evaluated by the JIP-test was observed. The two parameters might provide a basis to rank the plants according to their tolerance to light stress conditions, i.e. the studied cultivars can be split into three groups with a different response to high light stress: tolerant, intermediate and sensitive

Die Notwendigkeit einer Lichtraktion für die Induktion photosynthetischer Aktivität

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Inhibition of photosystem II activities in soybean (Glycine max) genotypes differing in chilling sensitivity

AbstractDue to chilling sensitivity, minimum night temperatures represent the main constraint in soybean production in South Africa. In vivo quantification of photosystem II (PSII) function by direct chlorophyll fluorescence revealed that dark chilling (8°) inhibited PSII function in the extreme chill sensitive genotype, Java 29 (JAs) mainly by deactivating reaction centers and inhibiting the conversion of excitation energy to electron transport and electron transfer from reduced plastoquinone to the PSI end electron acceptors. Further analysis of the normalized fast fluorescence transients, revealed that in JAs, upon dark chilling, disengagement of the oxygen evolution complex (ΔVK band) occurred which coincided with a concomitant decrease in O2 evolution measured in vitro. The chilling resistant Maple Arrow (MAr), though one night cold stress lead to a decrease in fluorescence emission at 2ms (−ΔVJ band) indicating a decrease in the QA− concentration due to cold-induced slow-down of electron donation from P680, however showed clear signs of recovery after the second and third cold nights. The moderate chill sensitive genotype, Fiskeby V (FBm) responded in a fashion intermediate to above-mentioned extremes. A second experiment showed that in JAs the inhibitory effect increased with increasing time of exposure to light following dark chilling. Our data demonstrated that significant differences exist in the cold tolerance of different soybean genotypes: (a) In respect to activity criteria, expressed by the quantum yields for primary photochemistry φPo=TRo/ABS, for electron transport from photosystem II to photosystem I as φEo=ETo/ABS and the efficiency, φRo=REo/ABS, to reduce the end electron acceptors of photosystem I up to NADP; (b) In respect to stability criteria, dependent on structure and conformation, such as the capability of energetic cooperativity (grouping) among photosynthetic units quantified by the grouping probability for exciton movements within the energetically connected group of entire photosynthetic units. Therefore analyzing the O-J-I-P fluorescence transient according to the JIP-test offers a practical and sensitive in vivo screening test for dark chilling tolerance in soybean

Surface and electronic structure of MOCVD-grown Ga(0.92)In(0.08)N investigated by UV and X-ray photoelectron spectroscopies

The surface and electronic structure of MOCVD-grown layers of Ga(0.92)In(0.08)N have been investigated by means of photoemission. An additional feature at the valence band edge, which can be ascribed to the presence of In in the layer, has been revealed. A clean (0001)-(1x1) surface was prepared by argon ion sputtering and annealing. Stability of chemical composition of the investigated surface subjected to similar ion etching was proven by means of X-ray photoemission spectroscopy.Comment: 13 pages, 6 figure

Diabetic gastroparesis: Therapeutic options

Gastroparesis is a condition characterized by delayed gastric emptying and the most common known underlying cause is diabetes mellitus. Symptoms include nausea, vomiting, abdominal fullness, and early satiety, which impact to varying degrees on the patient’s quality of life. Symptoms and deficits do not necessarily relate to each other, hence despite significant abnormalities in gastric emptying, some individuals have only minimal symptoms and, conversely, severe symptoms do not always relate to measures of gastric emptying. Prokinetic agents such as metoclopramide, domperidone, and erythromycin enhance gastric motility and have remained the mainstay of treatment for several decades, despite unwanted side effects and numerous drug interactions. Mechanical therapies such as endoscopic pyloric botulinum toxin injection, gastric electrical stimulation, and gastrostomy or jejunostomy are used in intractable diabetic gastroparesis (DG), refractory to prokinetic therapies. Mitemcinal and TZP-101 are novel investigational motilin receptor and ghrelin agonists, respectively, and show promise in the treatment of DG. The aim of this review is to provide an update on prokinetic and mechanical therapies in the treatment of DG