Ammonium and nitrate nutrition inPlantago lanceolata andPlantago major L. ssp.major

P. lanceolata andP. major were grown in culture solutions with nitrate or ammonium as the nitrogen source. Dry matter accumulation in the shoot was faster with nitrate than with ammonium, whilst that of the roots was not affected by the nitrogen source. As a consequence, the shoot-to-root ratio was lower with ammonium than with nitrate. InP. lanceolata, dry matter percentage of shoot and root tissue was lower with nitrate nutrition, suggesting better elongation growth than with ammonium. However, in shoot tissue ofP. major the opposite was found. The rate of root respiration declined with time, and this was almost completely due to a declining activity of the alternative path, which amounted to about 30–60% of total root respiration. Respiration via the cytochrome path was for a part of time slightly increased by ammonium, whereas the activity of the alternative path was strongly enhanced. The concentration of ethanol-soluble carbohydrates (SC) in the roots of both species was higher when nitrate was used, but no difference in the concentration of starch was found. When the plants were transferred from one nitrogen source to the other, many parameters, including the concentration of nitrate and chloride, and the shoot to root ratio, adjusted to the new situation in both species. Grassland Species Research Group, Publication no. 116.     

Alteration of growth ofSolanum opacum andPlantago drummondii and inhibition of regrowth of hyphae of vesicular-arbuscular mycorrhizal fungi from dried root pieces by manganese

Addition of MnSO₄ or MnCl₂ to a fine sandy soil from South Australia had a negative effect on shoot growth and root elongation ofSolanum opacum in the absence of significant presence of vesicular-arbuscular mycorrhiza (VAM). VAM ameliorated the reduction of plant growth by Mn, even though mycorrhizal development was decreased. Mn inhibited infection of roots by a fine endophyte less than that by some coarse endophytes. High concentrations of available Mn inhibited growth of hyphae of VAM fungi from dried root pieces, a significant source of infection by mycorrhizal fungi in the soil used.     

No evidence for a pleiotropic relationship between male sterility and cyanide-resistant respiration in Plantago lanceolata

Gynodioecy, the coexistence of hermaphrodites and male steriles, is frequent in populations of Plantago lanceolata L. A condition for the maintenance of gynodioecy in an obligatory outbreeding species like this is an increase in female fitness in male steriles compared with hermaphrodites. One of the possible underlying mechanisms, a lower cyanide-resistant respiration in male steriles, which could lead to a higher metabolic efficiency, was investigated. For the experiments adult plants were used, because the effects which compensate for male sterility have been found in characters like seed production and longevity. No general correlation between sex phenotype and cyanide-resistant respiration capacity, or with any other respiration component, was found. Only in a single cross a strong correlation between cyanide-resistant respiration activity and sex phenotype was established, male steriles possessing the higher activity. The conclusion from these experiments is that there is no pleiotropic relationship between respiration levels and sex phenotype. The strongly significant correlation mentioned is ascribed to chromosomal linkage.     

Effects of vesicular-arbuscular mycorrhizal infection and phosphate on Plantago major ssp. pleiosperma in relation to internal cytokinin concentrations

Relations between cytokinin concentrations and effects of P and vesicular-arbuscular mycorrhizal (VAM) infection were investigated in Plantago major L. ssp. pleiosperma Pilger. Both mycorrhizal infection by Glomus fasciculatum (Thaxt. sensu Gerdemann) Gerdemann and Trappe and P addition increased the shoot to root ratio, specific leaf area (SLA), and P concentrations of shoot and roots, and decreased the percentage of dry matter in the shoot during the experiment. In general, P concentration in the shoot and roots of each treatment correlated positively with the shoot to root ratio and specific leaf area, and negatively with the percentage of dry matter in the shoot. Cytokinin concentrations in the tissue of shoots and roots were determined using an enzyme-linked immunosorbent assay. Concentrations of zeatin and zeatin-ribosides in the free base and nucleotide fractions had increased more after P addition than in the case of mycorrhizal infection in both shoot and roots, whereas the P concentrations had increased less. It is suggested that zeatin and zeatin-ribosides are not the primary growth-substances involved in mediating VAM effects.     

Effects of rhizosphere soil,vesicular-arbuscular mycorrhizal fungi and phosphate onPlantago major L. ssp.pleiosperma Pilger

Biotic factors in the rhizosphere and their effect on the growth ofPlantago major L. ssp.pleiosperma Pilger (Great plantain) were studied. In a pot experiment the effect on shoot growth of the addition of 2.5% rhizosphere soil at four levels of phosphate was highly dependent on the availability of phosphate: a promoting effect at low phosphate levels was observed while a reducing effect occurred at higher phosphate levels. As the roots were infected with vesicular-arbuscular mycorrhizal (VAM) fungi in the treatment with rhizosphere soil, two other experiments were set up to separate effects of the indigenous VAM fungi from effects of the total rhizosphere population. The uptake of phosphate and shoot growth was not decreased at higher phosphate availability when VAM inoculum was added alone or in combination with rhizosphere soil. The growth reducing effect of the rhizosphere soil could therefore not be ascribed only to mycorrhizal infection. The results suggest that biotic factors in the rhizosphere soil affect the phosphate uptake ofPlantago major ssp.pleiosperma. This may, under conditions of phosphate limitation, lead to an increase of phosphate stress and, subsequently, a growth reduction. Futhermore, it is concluded that VAM fungi, as part of the rhizosphere population, may compensate this phosphate stress by enhancing the phosphate uptake.Grassland Species Research Group Publication No. 148.     

Variation in host susceptibility among and within populations ofPlantago lanceolata L. infected by the fungusPhomopsis subordinaria (Desm.) Trav.

Summary Susceptibility toPhomopsis stalk disease ofPlantago lanceolata genotypes, sampled in three different populations with a variable degree of infection by the fungusPhomopsis subordinaria, was determined under greenhouse conditions. Susceptibility of the host varied within, but not among populations. No relationship between the intensity of the disease in the field and the mean susceptibility of the host genotypes sampled at those locations could be established. Host susceptibility appeared to be composed of the host genotypes sampled at those locations could be established. Host susceptibility appeared to be composed of different (uncorrelated) plant characteristics. Determining whether host genotypes are highly or slightly susceptible can only be achieved by field trials, where the plants are exposed to the whole set of disease inducing factors. The relevance of host susceptibility to the intensity of disease in the field is discussed in relation to the variation in pathogenicity of the fungus and the variation in environmental factors prevailing inP. lanceolata populations underP. subordinaria pathogen pressure. Grassland Species Research Group Number 123     

Behaviour of specialist and generalist caterpillars on plantain (Plantago lanceolata)

Abstract.

• 1 Foraging patterns of specialist (Junonia coenia Hubner: Nymphalidae) and generalist (Spilosoma congrua Wlk.: Arctiidae) caterpillars on five genotypes of plantain (Plantago lanceolata L.: Plantaginaceae) were examined in an experimental garden.
• 2 Movement by the specialists reflected declining availability of new leaves. When direct sunlight was available, these caterpillars were usually exposed to it.
• 3 Although the generalists also preferred new leaves, they spent less than 50% of their time on the plantain and changed location more frequently than the specialists. They often hid at the base of plants or under leaves.
• 4 Plant genotype influenced the apparency of the specialists and damage by the herbivores.

     

Free proline accumulation in drought-stressed plants

Summary Free-proline accumulation was measured in leaves of intact wheat (Triticum vulgare L. cv. Kalyan Sona), plantago (Plantago ovata Forsk-Isabgool), papavar (Papaver somnifera L. Opium poppy) and mustard (Brassica juncea L. var. Varuna) grown in the field with low to high field water content and thus they were subjected to water stress. Leaf water deficit in percentage was used to determine the degree of stress at the time of proline anlysis.Free proline content was higher in mustard leaves as compared to wheat, plantago and papavar leaves. Water stress enhances the proline content but at same water deficit level the content differ in the leaves of the plants studied.