Michael Knee

Cadmium and Copper Uptake and Translocation in Five Willow (Salix L.) Species

ABSTRACT The efficacy for phytoremediation of five willow species was tested by experimental copper and cadmium uptake in a greenhouse hydroponic system. Five treatments included two concentrations (5 and 25 μM for each metal) and a control. Metal concentrations in solution as well as solution uptake were monitored. Metal resistance was assessed through effects on the dry weight of roots and shoots. The willow species tested were generally resistant of increased Cu and Cd content. Metal accumulation was found in all plant organs of all species. Growth and transpiration were not decreased by 5 μM of copper and 25 μM of cadmium in the solution for most species. 25 μM copper caused injury and reduced the dry weight for all species after 21 d. Salix nigra was highly resistant of both Cu and Cd and accumulated more metals than other species. Future field study should be conducted to confirm the findings and feasibility of the phytoremediation technology using those species.

Selection of biocides for use in floral preservatives

Abstract The effects of concentrations of various biocides, in a solution containing 0.2 g l−1 citric acid and 10 g l−1 glucose, were tested on cut roses (Rosa hybrida L., ‘Classy’), Alstroemeria pelegrina L. and carnations (Dianthus caryophyllus L.). Compounds were evaluated for their effects on flower life (time to decline in fresh weight), maximum gain in fresh weight, solution uptake from 4 to 6 days, resistance to water flow in the stem, stem respiration and solution absorbance. Longer flower life and higher gain in fresh weight of roses were observed with a concentration of 0.05 g l−1 than with higher concentrations of most biocides. At this concentration, bromopropanediol, Dantogard and thiabendazole did not prevent a rise in stem resistance to water flow, or solution absorbance. Aluminium sulphate up to 0.8 g l−1 was also ineffective in these respects. Stem respiration was inhibited by sodium benzoate, hydroxyquinoline citrate (HQC), Isocil and Physan-20. Principal component analysis on the rose data indicated that the best treatments were 0.05 g l−1 benzoate, cetylpyridinium chloride, Isocil and Physan-20, 0.05 and 0.2 g l−1 dichloroisocyanuric acid, and 0.2 and 0.8 g l−1 HQC. Tests with carnation and Alstroemeria indicated that HQC, Isocil and Physan most consistently promoted fresh weight increase and maintenance.

Vermicompost stimulates mycorrhizal colonization of roots of Sorghum bicolor at the expense of plant growth

Summary Two greenhouse experiments were conducted on the biological and nutritional effects of vermicompost on Sorghum bicolor growth and root infection by arbuscular mycorrhizal fungi (AMF). Two rates of sterile and non-sterile vermicompost (5% and 20%) were added to two media (peat and mineral). In experiment 1, all treatments received AMF inoculant but in experiment 2 uninoculated treatments were included. The addition of vermicompost to substrates increased N, P and K levels. Vermicompost stimulated mycorrhizal colonization of roots in both experiments, particularly in the peat medium. Shoot and root dry weights were increased by vermicompost in the absence of AMF. Inoculation with AMF reduced dry weights particularly at the higher rate (20%) of vermicompost. Steam sterilization of vermicompost had no consistent effect on mycorrhizal colonization but generally enhanced dry weights relative to the non-sterile treatment.

Carotenol esters in developing apple fruits

Abstract The carotenol esters of apple ( Malus pumila , cv Coxs Orange Pippin) fruit peel were partially characterized, and their accumulation measured relative to changes in ethylene concentration. Monoesters of violaxanthin, neoxanthin and an unknown pigment, possibly cryptoxanthin 5,6,5′,6′-epoxide, were found. Lutein, violaxanthin and neoxanthin were present as diesters. Palmitate and oleate were the main acyl substituents, with lesser amounts of laurate, myristate and stearate. There were large families of diesters, presumably including mixed fatty acyl derivatives, and these were not fully resolved by reverse phase HPLC. The pattern of acyl substitution appeared to recur among the mono- and diesters of the different carotenols. Violaxanthin mono-oleate and palmitate began to accumulate ca 20 days before the rise in ethylene production associated with fruit ripening, whereas the increase in the corresponding diesters was concurrent with the rise in ethylene. The results suggest that carotenol esters are synthesized de novo in ripening apples and that synthesis may be independent of ethylene or require lower concentrations to initiate than other ripening processes. The pigments could serve as early indicators of fruit maturity.

Role of ethylene in chlorophyll degradation in radish cotyledons

The effect of age of radish seedlings on changes in chlorophyll concentration caused by ethylene was examined. Ethylene was produced at 2–4 nl g−1 h−1 following excision of cotyledons from 5-to 20-day-old seedlings. The youngest cotyledons maintained this rate, whereas ethylene synthesis declined by as much as 80% during a 24-h period in older cotyledons. The youngest cotyledons continued to accumulate chlorophyll in the dark, but after 7 days cotyledons lost chlorophyll and the proportion of chlorophyll lost increased with age. Ethylene promoted, and norbornadiene inhibited, this loss of chlorophyll; in combined treatments the effects of ethylene and norbornadiene were competitive. The maximal rate of chlorophyll loss occurred in 1μl L−1 ethylene; extrapolation of the response to concentration indicated that half-maximum loss would occur at 0.005–0.01 μl L−1 ethylene. In cotyledons from 20-day-old seedlings, chlorophyll degradation occurred mainly after 24 h from excision and transfer to the dark. Chlorophyll degradation during 48 h in the dark was affected by norbornadiene or ethylene applied from 0–24 h or from 24–48 h.

Light utilization and competition between Echinacea purpurea, Panicum virgatum and Ratibida pinnata under greenhouse and field conditions

Competitive interactions were compared under field and greenhouse conditions for three representative tallgrass prairie species, Echinacea purpurea, Panicum virgatum and Ratibida pinnata. These were planted in monoculture and in mixtures of two species using a replacement series design with groups of four or eight plants. Competition was determined from shoot dry weight data collected during 120 days in the greenhouse and after 415 days in the field. Yields declined with increased density of a single species in the greenhouse from 40 days onward and in the field. Relative yields were up to 100% higher in mixtures than in monocultures for all species early on in the greenhouse experiment. Later in the experiment and in the field relative yields of E. purpurea decreased in the presence of P. virgatum and R. pinnata, whereas relative yields of these two species increased in the presence of E. purpurea. There were correlations in relative yield between the field and the greenhouse experiment at 80 and 120 days. In the greenhouse P. virgatum maintained higher net assimilation rates than the other species. Relative growth rates of all species were higher in monoculture and in mixtures up to 40 days, after which they declined, especially for E. purpurea in mixtures. In the field, higher light intensities occurred in pure stands of E. purpurea than in mixed stands with other species. The order of competitive ability that was apparent from these field and greenhouse studies, P. virgatum = R. pinnata > E. purpurea, could be partially explained by photosynthetic rates in relation to canopy light interception.

Evidence for a cytosolic NADP-malic enzyme in tomato

Abstract The similarity and cellular location of NADP + -malic enzyme (NADP-ME, EC 1.1.1.40) in developing fruit and other parts of the tomato ( Lycopersicon esculentum Mill.) plant were investigated in order to clarify the role of the enzyme in metabolism. There appeared to be a single enzyme (native NW 260 kD, subunit MW 66 kD) in mature green tomato fruit; this was purified to a specific activity of 42.5 μmol mg −1 min −1 and apparent homogeneity on SDS-PAGE. Polyclonal antibodies raised against this protein achieved 90% precipitation of enzyme activity, but required purification in order to detect specifically the 66 kD protein on Western blots. The purified antibodies recognized a similar protein in tomato leaves, roots and stems. The specific activity of NADP-ME was at least nine times higher in supernatant than in chloroplast fractions in tomato fruit and leaf, consistent with the distribution of a cytoplasmic marker (alcohol dehydrogenase), but in contrast to a chloroplast marker (rubisco). The purified NADP-ME antibodies did not detect a 66 kD protein in chloroplast preparations. A partial NADP-ME cDNA isolated from a fruit library specifically hybridized with a 2.1 kb transcript in RNA preparations from tomato leaves and fruits at different stages of development. The existence of a minor, possibly chloroplastidic NADP-ME in tomato cannot be excluded; the major NADP-ME is a cytosolic protein which is present in all plant organs analysed.

Sensitivity of ATPases to silver ions suggests that silver acts outside the plasma membrane to block ethylene action

Abstract The possibility of inhibition of ATPases, when silver salts are used to inhibit ethylene action in plant tissues, was considered. The vanadate-sensitive ATPase in a plasma membrane preparation was sensitive to 1 μM silver nitrate. Inhibition was reversed by a 20-fold excess of sodium thiosulphate, or dithiothreitol, but not by EDTA. This ATPase was also inhibited by silver nitrate in the presence of a four- or eight-fold excess of sodium thiosulphate. Mitochondrial ATPases appeared to be less sensitive than the plasma membrane enzymes to silver nitrate, but more sensitive to silver thiosulphate mixtures. Dilution of silver thiosulphate increased its inhibitory effect. Silver above 10 μM promoted ion and sugar efflux from corn coleoptile segments, but tissue respiration was only inhibited at 500 μM silver. It is suggested that ethylene action is inhibited by silver acting outside the plasma membrane.

Changes in mRNA during low temperature storage and ripening of pears

Abstract A method is described for the purification of nucleic acid from conference pear fruit. RNA was extracted from preclimacteric pears prior to storage, 60 days after storage at −1° and during the early stages of post storage ripening. In vitro translation of this RNA indicated that it was intact and showed a number of m RNA changes were occurring during both storage and subsequent ripening. Notable was the accumulation during storage of m RNAs coding for polypeptides with M r of ca 38, 44 and 45 000, and during the first 48 hr out of store a m RNA coding for a polypeptide with an M r of ca 43 000. The results show that low temperature storage and subsequent ripening of conference pears are accompanied by altered gene expression.

Relationship of seed source and arbuscular mycorrhizal fungi inoculum type to growth and colonization of big bluestem (Andropogon gerardii)

Big bluestem (Andropogon gerardii) is a key grass of tallgrass prairies and is commonly included in restoration projects. In many cases, it has been found to benefit significantly from arbuscular mycorrhizal (AM) fungi, however results have varied under non-sterile soil conditions. This study investigated the effects of two types of AM fungi inoculum (commercial and prairie) on growth and root colonization of big bluestem from five different seed sources grown in non-sterile soils. Seed sources were collected from five remnant prairies in the Tallgrass Prairie Peninsula located in the Midwestern United States. Growth of big bluestem and root length colonized by AM fungi was highly variable among seed source treatments. Overall, percentage of root length colonized by AM fungi was positively correlated with the total dry weight of plants, and plants that received inoculum generally grew better than those that did not receive inoculum. Inoculum treatment affected both big bluestem growth and percentage root length colonized and there was an interaction between seed source and inoculum treatment relative to colonization. Root colonization responses were not significantly different between the prairie and commercial inoculum types, although there was a significant response between plants that received additional inoculum as opposed to no additional inoculum. Seed sources from Ohio and Illinois had the highest biomasses and greatest percentage of root length colonized while plants from Wisconsin and Missouri grew poorly and had low root colonization. These results demonstrate the importance of considering both seed source and inoculum type before the incorporation of AM inoculum to prairie restoration projects.