Lobeline production by hairy root culture of Lobelia inflata L.

Hairy roots were obtained following inoculation of the stems of Lobelia inflata L. with Agrobacterium rhizogenes strain ATCC 15834. These hairy roots contained agropine and mannopine. In addition, lobeline was detected by HPLC and confirmed by mass spectrometry. Various media were tested for the growth of hairy roots as well as for the content of lobeline in hairy roots. The growth rate of hairy roots cultured in Nitsch and Nitsch's medium was approximately one third of those cultured in other media. The lobeline content of hairy roots (18–54 g/g dry weight) cultured in these media was the same order of magnitude compared with that of roots of L. inflata (24 g/g dry weight) cultivated in pots. The hairy roots cultured in Nitsch and Nitsch's medium were morphologically different from those cultured in other media.Abbreviations MS medium Murashige and Skoog's medium - 1/2 MS medium one-half strength of the standard Murashige and Skoog's medium - B5 medium Gamborg's B5 medium - NN medium Nitsch and Nitsch's medium - FW fresh weight - DW dry weight     

Control of hypocotyl phototropism by phytochrome in a dicotyledonous seedling (Sesamum indicum L.)

Abstract The phototropic response in stems of higher plants is brought about by blue/UV light. The problem studied here is to what extent long-wavelength light, which is absorbed by phytochrome, affects the phototropic response. A refined measurement of phototropism — a curvature index — was applied to the hypocotyl of the sesame seedling (Sesamum indicum L.). The time course of the phototropic response was followed in continuous unilateral weak blue light (B, 460 nm, 8 mW m^?2). Long term red light (R) pretreatments, operating through phytochrome, strongly increase the rate and extent of the phototropic response once it is elicited by unilateral B, while the pretreatments decrease the sensitivity towards B. If a R pulse is given immediately prior to the onset of unilateral B, the rate of the response is strongly reduced compared to the time course of curvature observed when the pretreatment was terminated with a long wavelength far-red light (FR) pulse. R and FR were then applied simultaneously with unilateral B to manipulate the status of the phytochrome system during actual curvature. It was found that a low Pfr/P ratio (established by FR) stimulates the phototropic response far above the control (B alone), while a high Pfr/P ratio (established by R) reduces the response below the control. During bending a positive effect of phytochrome on the rate and extent of the phototropic response, which is saturated at a low level of Pfr, appears to be counteracted by an inhibitory effect which dominates at higher levels of Pfr, such as established by omnilateral R. However, if R is applied unilaterally from the same direction as B, R increases the rate of curvature. Apparently the sesame seedling is capable of detecting the direction of R relative to the direction of B. While a mechanistic explanation of these effects cannot be advanced at present, it is clear that the seedling is capable of super-imposing information about the actual light conditions during bending on a ‘memory’ of the light conditions prior to the onset of bending. Thus, the previous as well as the actual light conditions determine its phototropic responsiveness.     

Analysing partitioning of recently fixed and of reserve carbon in reproductive Phaseolus vulgaris L. plants

Abstract. Partitioning of recently-fixed carbon among plant organs and subsequent distribution of reserve carbon were studied by supplying whole shoots of bean plants ( Phaseolus vulgaris L.) with ¹⁴C-labelled CO₂ of constant specific radioactivity throughout a photoperiod. The gain of tracer carbon in each part revealed net accumulation of recently-fixed carbon from direct fixation, import or both. Growth rate coefficients describing the present pattern of plant growth were calculated from ratios of tracer carbon to total carbon present in plant organs and were used to project future plant form. The period 10–20 d after the start of flowering was marked by a major increase in partitioning of recently-fixed carbon to reproductive growth. Growth rates for the plant and its parts during this period were projected on the basis of growth rate coefficients and were found to be similar to rates measured by gravimetric growth analysis. Changes in tracer carbon recovered in individual organs after chase periods of various lengths revealed net decreases for leaves and stems. About 9% of the carbon distributed to fruits came from reserves even in the absence of obvious stress. Respiratory loss during the chase period was determined from the progressive drop in recovery of the original tracer carbon. The methods are being applied to measure current net accumulation rates in studies of sink organ physiology, and to compare partitioning of recently-fixed and of stored carbon in several plant species under defined growth conditions.     

Proteolytic specificity of chicken cathepsin L on bovineβ-casein

The proteolytic specificity of chicken cathepsin L was studied using bovine -casein as substrate. The peptide mixtures obtained after various times of hydrolysis were separated by RP-HPLC and ten peptides were identified. Chicken cathepsin L accepts proline residues in all positions except P ₁ . Looking at the amino acid residues on the amino side of the scissile bond we found three times the Tyr-Pro pair at P ₁ –P ₂ positions and that the S ₁ subsite can interact with modified amino acids such as phosphoserine.Abbreviations RP-HPLC reverse phase high performance liquid chromatography - NMec N-methyl coumarylamide - TEA triethylamine - TFA trifluoroacetic acid     

Rice cultivar evaluation for phosphorus use efficiency

Phosphorus deficiency is one of the most growth-limiting factors in acid soils in various parts of the world. The objective of this study was to screen 25 rice cultivars (Oryza sativa L.) at low, medium, and high levels of soil P. Number of tillers, root length, plant height, root dry weight and shoot dry weight were related to tissue P concentrations, P uptake and P-use efficiency. Shoot weight was found to be the plant parameter most sensitive to P deficiency. Significant cultivar differences in P use efficiency were found. Phosphorus use efficiency was higher in roots than shoots and decreased with increasing levels of soil P. Positive correlations were found among growth parameters such as plant height, tillers, root and shoot weight, and P content of roots and shoots. These results indicate selection of rice cultivars for satisfactory performance under low P availability can be carried out using shoot and root dry weight as criteria.     

Chloroplast proliferation based on their distribution and arrangement inAdiantum protonemata growing under red light

Chloroplast proliferation was investigated inAdiantum protonemata growing under continuous red light. Cell division is absent when cells are grown under red light. The chloroplast number increases as the cell length increases, therefore the chloroplasts divide in the absence of cell division. Chloroplasts in the basal part of the filamentous protonemal cell migrate gradually toward the cell apex, but there is no large net migration from the tip to the base or vice versa, indicating that chloroplast division takes place in the apical part of the protonemata. Chloroplast number in the apical 100 μm was maintained at about 200 during cell growth at least over eight days. The chloroplasts were either dumbbell- or ellipsoid-shaped. Dumbbell-shaped chloroplasts are abundant everywhere in a protonema, ranging from 30 to 50% of the total chloroplasts. The dumbbell-shaped chloroplasts attached to or very close to the plasma membrane seem to be the ones that are dividing but the dumbbell-shaped ones in the other regions do not divide. These data support the hypothesis that a signal from the plasma membrane induces the dumbbell-shaped chloroplasts to divide.     

Differences in learning by foraging juvenile pumpkinseed and bluegill sunfish in a structured habitat

Synopsis We investigated the ability of two congeneric species of sunfish to learn to forage on a novel prey item in feeding arenas containing structured habitats. Eight bluegill sunfish and eight pumpkinseed sunfish were given the opportunity to forage on whiteworms daily for 10 days. Each day, several behavioural measures were recorded for each fish. Both species of sunfish learned to feed over the 10-day period but the bluegill sunfish learned to feed more quickly than the pumpkinseed sunfish. Pumpkinseeds, however, attained a higher level of foraging efficiency. The differences in learning and foraging efficiency were related to body morphology.     

Lipolytic and peroxidative enzyme expressions in cultured potato tuber cells

Potato cells (cv. Norchip) were cultured from tuber parenchymal tissue and subcultured to dissociate and habituate the despecialized cells. After several subculturings on a minimal nutrient media, this line of cells demonstrated repeatable physical growth profiles for dry weight (DW), fresh weight (FW) and protein. Two enzymes of plant lipid metabolism were investigated, lipolytic acyl hydrolase (LAH) and lipoxygenase (LOX), which respectively liberate and peroxidize fatty acids from lipid in cellular membranes. LAH, measured as p-nitrophenyl palmitate hydrolase, was present in this line of cells in easily detectable amounts (317 units g^-1 DW) albeit much lower than that found in mother tuber (9878 units g^-1 DW). The presence of LAH in this line is significant because LAH isozymes are often described as storage proteins, yet activity per gram fresh weight in these unorganized cells is reasonably constant until culture growth exits the linear phase. However, LOX, the most active free fatty acid metabolizing enzyme in potato tubers (89,800 units g^-1 DW), was not detectable in this line of callus or suspension cultured cells. The absence of LOX activity in this line of cells was verified by a number of assay approaches and was confirmed by activity staining of extracted enzymes separated in polyacrylamide gels. The absence of LOX in these cultured cells is especially important in determining the functions of this lipid peroxidation system and how it may be genetically regulated.Mention of company or trade name does not imply endorsement by the United States Department of Agriculture over others not named.A laboratory cooperatively operated by the Midwest Area, Agricultural Research Service, U.S. Department of Agriculture, The Minnesota Agricultural Experiment Station, the North Dakota Agrcultural Experiment Station, and the Red River Valley Potato Grower's Association.     

Root turnover and production by14C dilution: implications of carbon partitioning in plants

Summary Estimates of belowground net primary production (BNP) obtained by using traditional soil core harvest data are subject to a variety of potentially serious errors. In a controlled growth chamber experiment, we examined the aboveground-belowground, labile to structural tissue, and plant to soil dynamics of carbon to formulate a¹⁴C dilution technique for potential successful application in the field and to quantify sources of error in production estimates.Despite the fact that the majority of net¹⁴C movement between above- and belowground plant parts occurred between the initial labeling and day 5, significant quantities of¹⁴C were incorporated into cell-wall tissue throughout the growing period. The rate of this increase at late sampling dates was greater for roots than for shoots. Total loss of assimilated¹⁴C was 47% in wheat and 28% in blue grama. Exudation and sloughing in wheat and blue grama, respectively, was 15 and 6% of total uptake and 22 and 8% of total plant production.When root production estimates by¹⁴C dilution were corrected for the quantities of labile¹⁴C incorporated into structural carbon between two sampling dates, good agreement with actual production was found. The error associated with these estimates was ±2% compared with a range of –119 to –57% for the uncorrected estimates. Our results suggest that this technique has potential field application if sampling is performed the year after labelling.Sources of errors in harvest versus¹⁴C dilution estimates of BNP are discussed.