Showing papers on "Plant morphology published in 2006"

Plant morphology and root hydraulics are altered by nutrient deficiency in Pistacia lentiscus (L.)

Abstract: The plants in arid and semiarid areas are often limited by water and nutrients. Morpho-functional adjustments to improve nutrient capture may have important implications on plant water balance, and on plant capacity to withstand drought. Several studies have shown that N and P deficiencies may decrease plant hydraulic conductance. Surprisingly, studies on the implications of nutrient limitations on water use in xerophytes are scarce. We have evaluated the effects of strong reductions in nitrogen and phosphorus availability on morphological traits and hydraulic conductance in seedlings of a common Mediterranean shrub, Pistacia lentiscus L.. Nitrogen deficiency resulted in a decrease in aboveground biomass accumulation, but it did not affect belowground biomass accumulation or root morphology. Phosphorus-deficient plants showed a decrease in leaf area, but no changes in aboveground biomass. Root length, root surface area, and specific root length were higher in phosphorus-deficient plants than in control plants. Nitrogen and phosphorus deficiency reduced both root hydraulic conductance and root hydraulic conductance scaled by total root surface area. On the other hand, nutrient limitations did not significantly affect root conductance per unit of foliar surface area. Thus, adaptation to low nutrient availability did not affect seedling capacity for maintaining water supply to leaves. The implications for drought resistance and survival during seedling establishment in semi-arid environments are discussed.

Modulation of plant morphology, root architecture, and cell structure by low vitamin C in Arabidopsis thaliana

Abstract: Ascorbic acid (AA) fulfils many essential functions in plants. It is a key antioxidant and an important reducing substrate for a number of enzymes. The effects of low AA on plant architecture and leaf ultrastructure were studied in Arabidopsis thaliana mutants, which have constitutively moderately low (vtc1) or very low (vtc2) leaf AA contents compared with the wild type. Shoot development was comparable in all accessions over the first 14 d of growth. The production of primary roots was slightly different in vtc1, vtc2, and wild-type plants. However, the most notable difference was that a high proportion of the primary roots of the vtc2 plants grown on soil had lost the wild-type responses to gravity. The vtc mutants showed the antagonistic interaction between nitrate and sugar in the regulation of lateral root (LR) development that was observed in the wild type. However, the vtc2 mutants produced greater numbers of longer LRs than wild-type or vtc1 plants at all levels of nitrate. At later stages of development, the vtc rosettes were smaller than those of the wild type and the leaves showed intracellular structural changes that are consistent with programmed cell death (PCD). PCD symptoms such as nuclear chromatin condensation, the presence of multivesicular bodies, and extensive degradation and disorganization of the grana stacks were observed in 8-week-old vtc2 leaves and in 10-week-old vtc1 leaves. The data presented here illustrate the importance of tissue AA contents in regulating whole plant morphology, cell structure, and development.

Morphological Diversity of Bambara Groundnut [ Vigna subterranea (L.) Verdc.] Landraces in Tanzania

Abstract: A field experiment was conducted in Tanzania for two seasons to assess the genetic diversity of bambara groundnut landraces based on morphological characters. One hundred accessions collected from a wide range of agricultural zones in the country were evaluated in a 10 × 10 triple lattice block design at Maruku station in Bukoba, Tanzania. For the qualitative characters evaluated, considerable morphological variations were observed for growth habit, pod shape and pod colour. Quantitative morphological characters such as peduncle length, number of leaves per plant, terminal leaflet width, terminal leaflet length, petiole length, plant spread, plant length, pod width, seed length, seed width, number of pods per plant, shelling percentage and days to 50% flowering showed significant variation among accessions for the two test seasons. Multivariate analysis for 15 quantitative morphological traits that showed significant variation indicated that the first four PCs with eigenvalues ≥1 accounted for 63.0 and 65.0% of the total variance among the accessions during the two test seasons, respectively. The most important loadings for PC1 and PC2 for the two seasons were terminal leaflet width, terminal leaflet length, petiole length, plant spread, plant height and pod length, pod width, seed length, seed width, numbers of pods per plant. Cluster analysis grouped bambara groundnut accessions into three major groups with respect to their geographic origins. Based on this present study, bambara groundnut landraces from Tanzania displayed a considerable diversity for morphological and agronomic traits useful for germplasm management and utilization into crop improvement.

Native and introduced populations of Solidago gigantea differ in shoot production but not in leaf traits or litter decomposition

Abstract: Summary 1Invasive alien plants tend to have a greater specific leaf area and more nutrient-rich tissues than the invaded native vegetation. To test whether these traits differ between introduced and native populations of the same species, we compared 20 European (introduced) and 22 American (native) populations of Solidago gigantea Aiton (Asteraceae) in a common-garden experiment. 2Five plants per population were grown for 2 years in pots and for one summer outdoors in nutrient-rich soil. We recorded shoot number and biomass, leaf production and senescence, flowering, leaf morphology and nutrient concentrations of leaves and litter. In laboratory assays, we compared litter decomposition and nutrient mineralization. 3Shoot growth and leaf traits varied three- to 10-fold among the 42 populations. European plants produced, on average, more shoots than American plants, but did not differ in shoot size, leaf traits or litter decomposition. 4The shoot number and total shoot biomass per plant in the experiment correlated positively with the number of new rhizomes produced by shoots of the same populations at their original field sites. 5We conclude that introduced S. gigantea populations tend to produce more shoots through clonal growth than native populations. This may increase their ability to compete against the established vegetation in dense stands or at nutrient-poor sites.

Effects of litter and standing biomass on growth and reproduction of two annual species in a Mediterranean old‐field

Abstract: Summary 1 We tested the hypothesis that the competitive ability of a plant changes during its lifetime, by evaluating variations in the relative influence of standing biomass and litter on plant performance. 2 Seedlings of two annual herbaceous species (‘targets’), of contrasted life-forms ( Crepis foetida and Bromus madritensis ) were transplanted into an old-field. The competitive ability of seedlings, vegetative and reproductive plants towards neighbours was recorded over one growing season. 3 Fourteen traits related to plant morphology, growth and reproduction were measured to assess the competitive ability of targets. Relationships among traits were characterized to identify a set of traits as a surrogate of target competitive ability. 4 The two target species responded similarly. Early growth was facilitated by litter and, to a greater degree, by vegetative biomass. Thereafter, the effect of neighbouring vegetation on target performance was negative, with a maximum depressing effect on reproduction (especially seed number and date of flowering) despite a weak facilitative effect of litter. Plant basal diameter, measured at peak growth period, and total number of inflorescences per plant, were found to predict growth and reproductive components of competitive ability, respectively. 5 Assessing the effects of competition for population success from the response of vegetative plants will underestimate its importance because competition appears to exert its maximal impact on seed production.