Sharon A. Duray

Influence of Phosphorus and Endomycorrhiza (Glomus Intraradices) on gas exchange and plant growth of Chile Ancho Pepper (Capsicum Annuum L. cv. San Luis)

Seedlings of chile ancho pepper were grown in pots containing a pasteurized mixture of sand and a low phosphorus (P) sandy loam soil, and either inoculated (VAM) or not inoculated (NVAM) with the endomycorrhizal fungus Glomus intraradices. Long Ashton nutrient solution (LANS) was modified to supply P to the seedlings at 0, 11, and 44 g(P) m-3 (P0, P11, P44, respectively). Low P depressed net photosynthetic rate (PN), stomatal conductance (gs), phosphorus use efficiency (PN/P), and internal CO2 concentration (Ci). The mycorrhiza alleviated low P effects by increasing PN, gs, PN/P, and decreasing Ci. At P0, Ci of NVAM plants was equal to or higher than that of VAM plants, suggesting nonstomatal inhibition of photosynthesis. Gas exchange of VAM plants at P0 was similar to that of NVAM plants at P11. Endomycorrhiza increased leaf number, leaf area, shoot, root and fruit mass at P0 and P11 compared to NVAM plants. Reproductive growth was enhanced by 450 % in mycorrhizal plants at P44. Root colonization (arbuscules, vesicles, internal and extraradical hyphae development) was higher at lower P concentrations, while sporulation was unaffected. The enhanced growth and gas exchange of mycorrhizal plants was in part due to greater uptake of P and greater extraradical hyphae development.

Micropropagation of Crinum 'Ellen Bosanquet' by tri-scales

Crinum lilies (Crinum spp. L.) are tropical and sub-tropical bulbous plants with excellent potential for southern US landscapes. Unfortunately, the more desirable crinum cultivars are slow and expensive to propagate by traditional offsets. The objective of this research was to develop reliable procedures for multiplying Crinum ‘Ellen Bosanquet’ by tissue culture. A sterilization procedure for cleaning explants was developed in which bulb chips containing a basal plate were submersed and agitated in 0.525% hypochlorite for 1 h. For shoot formation, tri-scales (three scales attached to a section of the basal plate) were used as the explant source and grown on MS-based media containing five levels of benzyladenine (BA) (0‐22.2 mM) and five levels of naphthaleneacetic acid (NAA) (0‐5.3 mM). The greatest shoot formation was obtained from the highest level of BA (22.2 mM) without NAA. In a subsequent experiment, explants were cultured for 4 months on media containing 35.5‐88.8 mM BA, and then transferred to hormone-free media for 3 months. BA at 35.5 mM stimulated optimal shoot (8.4) and bulblet (2.8) formation. Plantlets were successfully acclimatized and rooted ex vitro. # 1999 Elsevier Science B.V. All rights reserved.

Mycorrhizae, soil amendments, water relations and growth of Rosa multiflora under reduced irrigation regimes

Abstract To determine the role of endomycorrhizae and selected soil amendment treatments on water relations and growth of Rosa multiflora , rooted cuttings were planted in a medium with either incorporated hydrogel (polyethylene oxide) or a synthetic mulch surface covering (wax-impregnated cardboard) and either inoculated with vesicular-arbuscular mycorrhizal fungi (VAM) [ Glomus mosseae (Nicol. and Gerd.) and G. fasciculatum (Thaxt. sensu Gerd.) Gerd. and Trappe] or left as non-inoculated controls. Plants were initially irrigated daily, but then irrigation was reduced to three times weekly before water-stress cycles were initiated. Shoot and root dry weight and root:shoot ratio were higher when hydrogel was incorporated in the medium, regardless of VAM colonization treatments. Xylem water potential in shoots ( ψ s ) of roses with hydrogel-in-corporated medium was lowest (more negative) and had the greatest changes regardless of mycorrhizal treatment. In general, mycorrhizal plants had lower transpirational rates and a higher diffusive resistance, either with or without hydrogel incorporation in medium.

GROWTH, ROOT ALTERATION, AND NUTRIENT UPTAKE OF NEEM TREE (Azadirachta indica A. Juss) SEEDLINGS IN RESPONSE TO VESICULAR-ARBUSCULAR MYCORRHIZAL FUNGI AND PHOSPHORUS NUTRITION

SUMMARY Growth and nutrient uptake of neem tree (Azadirachta indica A. Juss) seedlings were studied in response to vesicular-arbuscular mycorrhizal (VAM) fungi Glomus intraradices Schenck and Smith, and 2 levels of phosphorus (P). Extensive VAM colonization in neem roots occurred at both P levels: 0.65 and 1.30 mM P. Growth of VAM plants at both P levels was similar, while growth of noncolonized (Non-VAM) plants increased with increasing P supply. At the low P level, VAM plants had greater leaf area, shoot, root and leaf dry weight, and a greater root: shoot ratio than Non-VAM plants. Low P, VAM plants had a greater leaf area and root dry weight and a comparable leaf and shoot dry weight and root: shoot ratio, when compared with high P, Non-VAM plants. VAM inoculation also altered dry mass partitioning to root systems resulting in greater root length and dry weight of suberized roots in VAM plants. The length of nonsuberized roots increased with increasing P supply regardless of VAM inoculation. VAM inocu...

Influence of Phosphorus on Gas Exchange and Plant Growth of Two Morphologically Distinct Types of Capsicum Annuum

Tolerance to phosphorus stress was studied in Capsicum annuum L. Chile ancho cv. San Luis and bell pepper cv. Jupiter plants. Plants were fertilized weekly with Long-Ashton nutrient solution (LANS) modified to supply 0, 11, 22, 44, 66, or 88 g(P) m-3 (P0, P11, P22, P44, P66, P88). Phosphorus stress occurred in both cultivars at P0 and P11, with reduced plant growth and development. At P0, the lowest percentage of total biomass was directed toward reproductive growth. The root/shoot ratio was greatest at P0, reflecting greater dry matter partitioning to the root system. Growth of ‘San Luis’ was more sensitive to phosphorus stress than ‘Jupiter’. A greater percentage of total biomass was directed towards reproductive growth in ‘Jupiter’ than ‘San Luis’. Increasing P nutrition elevated leaf tissue P in both cultivars with highest leaf tissue P at P88. There were no differences in tissue P between P0 and P11 ‘San Luis’ plants, whereas P0 ‘Jupiter’ plants had the lowest tissue P. Low P-plants generally had the highest tissue N and lowest S, Mn, and B. In both cultivars, gas exchange was lowest at P0, as indicated by reduced stomatal conductance (gs) and net photosynthetic rate (PN). Internal CO2 concentration and leaf-to-air vapor pressure difference (VPD) were generally highest with P-stressed plants. Phosphorus use efficiency, as indicated by PN per unit of leaf tissue P concentration (PN/P), was highest at P11. Generally, no P treatments exceeded the gas exchange levels obtained by P44 (full strength LANS) plants. Both PN and gs declined during reproductive growth in ‘San Luis’, which fruits more rapidly than ‘Jupiter’, whereas no reduction in gas exchange occurred with ‘Jupiter’.