On the races of Arenaria tetraquetra L. (Caryophyllaceae)

FAVARGER, C. & NIETO FELINER, G., 1988 On the races of Arenoria tetraquetra L. (Caryophyllaceae). The caryological study of some Betic populations of Arenaria tetraquetra northwards from Sierra Nevada has proved that they are polyploids ( 3x, 4x, 5x ). Even though their Rowers are pentamerous, they differ from the Nevadean Arenaria tetraguetra subsp. amabilis (2x ) not only by the chromosome number but also by the micromorphology of the seed coat and the hairiness of the stem internodes. They also differ from Arenaria tetraquetra subsp. tetraquetra , the Rowers of which are tetramerous and the degree of polyploidy higher (6x in the Pyrenees, 7x in the Sierra de Pela eastwards from Sierra de Guadarrama). The authors proposed to give a subspecific status to such Betic polyploid populations with a new combination. They suggest a hypothesis to explain the evolution of the A. tetraguetra polyploid complex.     

A revision of Arenaria section Plinthine (Caryophyllaceae)

GOYDER, D. J., 1987. A revision of Arenaria section Plinthine (Coryophyllaceae). The systematics of Arenaria section Plinthine are reviewed and a classification is presented, based on detailed field and herbarium studies. Members of the section are found on the mountains of SW Europe and N Africa. Seven taxa are recognized within five species: A. alfacarensis, A. tetraquetra subsp. tetraquetra, A. tetraquetra subsp. amabilis, A. armerina, A. aggregata subsp. aggregata, A. aggregata subsp. erinacea , and A. querioides. Arenaria armerina and A. aggregata subsp. erinacea are extremely polymorphic and include minor morphological variants which have been treated as separate species in previous systematic treatments of the group.     

氮过量吸收对地肤暗呼吸速率及相对生长速率的影响

为研究N过量吸收对植物生长的作用,以耐盐植物地肤(Kochia scoparia)作为研究对象,设置3个不同的施N处理,测量了不同生长时期的N含量、暗呼吸速率、生物量和相对生长速率(RGR)。结果表明:在N过量吸收的情况下,多余的N对暗呼吸速率并没有显著的影响,导致了暗呼吸中N的利用效率变低;单位质量暗呼吸速率与相对生长速率(RGR)有很好的线性相关,并且直线的斜率和截距并不受氮素过量吸收的影响,表明单位质量暗呼吸速率与RGR的关系不受施氮水平的影响;暗呼吸速率与总N的异速关系中,幂指数的大小与施N量相关,施N量越大对应的幂指数越小。     

Pollen discounting and the evolution of selfing in Arenaria uniflora (caryophyllaceae)

Although most models of mating system evolution assign a central role to the male transmission advantage of selfing genotypes, empirical data on the male fitness consequences of increased self-pollination are still uncommon. Here, I use measures of pollen import and export by focal plants in genotyped arrays to investigate the effects of floral morphology and pollination environment on self and outcross male function. Plants from an autogamous population of Arenaria uniflora (Caryophyllaceae) exhibit complete pollen discounting relative to closely related outcrossers, as do morphologically intermediate F1 hybrids between the two populations. However, the low cumulative male fitness of hybrids probably results from reduced pollen number or competitive ability, rather than a nonlinear relationship with floral morphology. When surrounded by selfers, plants from the outcrosser population self-fertilize at nearly the same rate as selfers (>80%), but have much lower self male fitness due to reduced fruit set. Because outcross siring success is also extremely low (<8%) in this treatment, these mate-limited outcrossers are at male fitness disadvantage to both pseudocleistogamous selfers and nonlimited outcrossers. The relative male fitness of plants with different mating systems appears dependent on the ecological context, as well as on morphological trade-offs.     

Cultivar differences in the rate of nitrate uptake by intact wheat plants as related to growth rate

Six Argentinian wheat ( Triticum aestivum L.) cultivars grown in nutrient solutions in controlled environment were compared for their nitrate uptake rates on a root dry weight basis. Up to 3-fold differences were observed among the cultivars at 16, 20 and 24 days from germination, either when measured by depletion from the nutrient solution in short-term experiments, or by total N accumulation in the tissue during 8 days.
No differences in total N concentration in root or shoots were found among cultivars. Although the different cultivars showed significant differences in shoot/root ratio and nitrate reductase activity (EC 1.6.6.1) in the roots, none of these parameters was correlated with the nitrate uptake rate. However, nitrate uptake was found to be positively correlated (r = 0.99) with the shoot relative growth rate of the cultivars. The three cultivars with the highest nitrate uptake rates and relative growth rates showed a positive correlation between root nitrate concentration and uptake. However, this correlation was not found in the cultivars with the lowest growth and uptake rates.
Our results indicate that the difference in nitrate uptake rate among these cultivars may only be a consequence of their differences in growth rate, and it is suggested that at least two mechanisms regulate nitrate uptake, one working when plant demand is low and another when plant demand is high.     

Nutrition and growth of coniferous seedlings at varied relative nitrogen addition rate

The growth of two provenances of Pinus sylvestris L. were compared with two provenances of Picea abies (L.) Karst. and with Pinus contorta Dougl. when grown in solution cultures with low nutrient concentrations. Nitrogen was added at different exponentially increasing rates, and the other nutrients were added at a rate high enough to ensure free access of them to the seedlings. During an initial period of the culture (a lag phase), when the internal nutrient status was changing from optimum to the level of the treatment, deficiency symptoms appeared. The needles yellowed and the root/shoot ratio increased. The initial phase was followed by a period of exponential growth and steady-state nutrition. The needles turned green again, and the root/shoot ratio stabilized at a level characteristic of the treatment. These patterns were the same as previously reported for other tree species. The relative growth rate during exponential growth was numerically closely equal to the relative nitrogen addition rate. The maximum relative growth rates were about 6 to 7.5% dry weight increase day^-1. This is a much lower maximum than for broad-leaved species (about 20 to 30% day^-1) under similar growth conditions. The internal nitrogen concentrations of the seedlings and the relative growth rates were stable during the exponential period. Close linear relationships were found between these parameters and the relative addition rate up to maximum growth. During steady state the relative growth rates of the different plant parts were equal. However, there were large differences between genotypes in absolute root growth rate at the same seedling size because of differences in root/shoot ratio. Lodgepole pine had the highest root growth rate, whereas that of Norway spruce, especially the southern provenance, was remarkably low. Yet, Norway spruce had a high ability to utilize available nutrients. In treatments with free nutrient access, growth allocation to the shoot had a high priority in all genotypes, but there was still a marked tendency for luxury uptake of nutrients. Nitrogen productivity (growth rate per unit of nitrogen) was lower than in broadleaved species and highest in lodgepole pine. The relevance of the dynamic factors, i.e. maximum relative growth rate, nutrient uptake rate, nitrogen productivity, growth allocation and root growth rate, are discussed with regard to conifer characteristics and selection value.     

Comments on the taxonomic treatment of Arenaria section Plinthine (Caryophyllaceae)

Comments on the taxonomic treatment of Arenaria section Plinthine (Caryophyllaceae) by D. J.Goyder. Comments are given on the taxonomic treatment of Arenaria section Plinthine presented by D. J.Goyder in a revision of this group recently published in the Botanical Journal of the Linnean Society, 97(1): 9–32.     

Environmental variation for outcrossing rate in rapeseed (Brassica napus)

Summary Rapeseed (Brassica napus) is a predominantly selfpollinated crop with about one-third outcrossing. The outcrossing rate may be influenced by environmental factors, and hence changes in the heterozygosity level of a variety may occur during multiplication. In an investigation on environmental variation in outcrossing, we estimated the outcrossing rate in the Swedish spring rapeseed cv Topas by isozyme analysis and found that outcrossing varied from 12% to 47% over five locations in Sweden, Denmark and Germany. Among flowers at different positions on the same plant, average outcrossing varied from 11% at the top to 39% at the bottom of the plant. In conclusion, environmental factors can greatly influence the outcrossing rate in rapeseed, and an investigation therefore merit further studies.     

Differences in developmental plasticity and growth rate among drought-resistant and susceptible cultivars of durum wheat (Triticum turgidum L. var. durum)

Understanding how growth and development of durum wheat cultivars respond to drought could provide a basis to develop crop improvement programmes in drought-affected tropical and subtropical countries. A greenhouse experiment was conducted to study the responses of five durum wheat cultivars to moisture stress at different developmental phases. Phenology, total dry matter (TDM), relative growth rate (RGR), leaf area ratio (LAR), net assimilation rate (NAR), leaf weight ratio (LWR), specific leaf area (SLA) and shoot:root ratio were compared. Pre-anthesis moisture stress delayed phenological development, whereas post-anthesis moisture stress accelerated it. TDM accumulation rate was different between drought-resistant and susceptible cultivars. RGR and its components changed with age and moisture availability. Drought-resistant cultivars had a high RGR in favourable periods of the growing season and a low RGR during moisture stress. In contrast, the drought-susceptible cultivar (Po) showed an opposite trend. LAR explained the differences in RGR (r=0.788) best, whereas the relationship between NAR and RGR was not significant. Even though both LWR and SLA were important factors determining the potential growth rate, LWR was of major importance to describe cultivar differences in LAR, and consequently in RGR. The drought-resistant cultivars Omrabi-5 and Boohai showed vigorous root development and/or a low shoot:root ratio. It is concluded that biomass allocation is the major factor explaining variation in RGR among the investigated durum wheat cultivars.     

Development and characterization of microsatellite markers for Arenaria grandiflora L. (Caryophyllaceae)

Genomic libraries of Arenaria grandiflora enriched for di- and trinucleotide repeats were used for the development of novel microsatellite markers. The subset of 13 polymorphic markers was characterized on 40 individuals of A. grandiflora originating from lowland locations in France. The loci amplified 3 to 10 alleles per locus and expected heterozygosities ranged from 0.46 to 0.83. The newly developed markers will be used for population genetic studies and for assessing genetic composition of a restoration experiment of lowland A. grandiflora populations that are protected in France.     

Relative growth rate and biomass allocation in 20 Aegilops (Poaceae) species

This paper analyses relationships between relative growth rate ( rgr ), seed mass, biomass allocation, photosynthetic rate and other plant traits as well as habitat factors (rainfall and altitude) in 20 wild species of Aegilops L. and one closely related species of Amblyopyrum (Jaub. & Spach) Eig., which differ in ploidy level (diploid, tetraploid and hexaploid). The plants were grown hydroponically for 20 d in a growth chamber. The relationships between parameters were calculated either using the phylogenetic information (phylogenetically independent contrasts, PIC) or without using the phylogenetic information (trait values of taxa, TIP). The results using the two approaches were very similar, but there were a few exceptions in which the results were different (e.g. rgr vs. seed mass). Specific leaf area ( sla ) was positively correlated with leaf area ratio ( lar ) and negatively correlated with net assimilation rate ( nar ), which together resulted in the absence of a correlation between sla and rgr . Leaf photosynthetic rates (expressed on a mass or area basis) showed no correlation with rgr . rgr was positively correlated with the stem mass ratio and negatively with root mass ratio. Species with a lower d. wt percentage have a higher rgr . Aegilops species from locations with higher annual rainfall invested less biomass in roots and more in shoots (leaves and stems) and had a higher rgr . Diploid species had a lower seed mass and initial mass than the hybrids (tetraploid and hexaploid species), but there was no correlation of rgr with ploidy level. Polyploid species, which have higher seed mass, occur at a higher altitude than diploid species. Our results show that variation in rgr in Aegilops and Amblyopyrum spp. is associated mainly with variation in biomass allocation (proportion of biomass in stems and roots) and d. wt percentage, and not with variation in sla , leaf photosynthetic rates or seed mass.     

Control of relative growth rate by application of the relative addition rate technique to a traditional solution culture system

The relative addition rate (RAR) technique allows the nutritional control of plant relative growth rate (RGR) by the provision of nutrients at exponential supply rates. The technique, however, was developed with technologically sophisticated aeroponic systems. In this paper, we report on experiments used to adapt the RAR technique to a conventional solution culture system. A background concentration requirement of 36 μM nitrogen (N), with other nutrients supplied in proportion to N, was necessary to produce a constant RGR of Triticum aestivum L. (wheat) at a low RAR. Solution pH changes were reduced by increasing the percentage of NH₄ in the nitrogen supply, but the plants exhibited dry weight reductions and symptoms of toxicity above 30% NH₄. For wheat, a ratio of 25/75 NH₄/NO₃ was optimum for minimizing pH changes within the nontoxic range. A test of the effectiveness of the RAR technique using this background concentration and NH₄/NO₃ ratio showed that RGR increased with RAR with a linear slope of 0.55 and an intercept of 0.07 d^-1. Although the relationship between growth rate and nutrient supply was less than the one-to-one dependence of RGR on RAR that has been obtained with more sophisticated apparatus, application of the RAR technique to a conventional solution culture system still affords considerable control of RGR and presents a simple method for growing plants at different levels of nutrient stress and at distinct RGRs.     

Variation in outcrossing rate and population genetic structure of Clarkia tembloriensis (Onagraceae)

Summary Outcrossing rate estimates for eight accessions of Clarkia tembloriensis indicate that this annual plant species has a wide interpopulational range of outcrossing rate ( ). Populations' t estimates were significantly correlated with observed heterozygosity and mean number of alleles per locus. Estimated fixation indices, , for most populations were very close to their expected values, F_eq, for a given Nei's gene diversity statistics showed that the group of outcrossing populations have more total genetic variation and less differentiation among populations than does the group of selfing populations. These results indicate that the breeding system of C. tembloriensis has had a strong influence on the amount and distribution of genetic variation within and among its populations.     

Chemical composition of 24 wild species differing in relative growth rate

The chemical composition of 24 plant species which showed a three-fold range in potential growth rate was investigated. The carbon content of whole plants was lower for fast-growing species than for slow-growing ones. Fast-growing species accumulated more organic N-compounds, organic acids and minerals, whereas slow-growing species accumulated more (hemi)cellulose, insoluble sugars and lignin. No correlations with relative growth rate were found for soluble phenolics, soluble sugars and lipids. The costs to construct 1 g of plant biomass were rather similar for fast- and slow-growing species, both when expressed as C needed for C-skeletons, as glucose to provide ATP and NAD(P)H, and as total glucose costs. Therefore, we conclude that, despite the differences in chemical composition between fast- and slow-growing species, variation in the costs of synthesis of whole plant biomass cannot explain interspecific variation in relative growth rate of herbaceous species.     

Simultaneous identification of growth law and estimation of its rate parameter for biological growth data: a new approach

Scientific formalizations of the notion of growth and measurement of the rate of growth in living organisms are age-old problems. The most frequently used metric, “Average Relative Growth Rate” is invariant under the choice of the underlying growth model. Theoretically, the estimated rate parameter and relative growth rate remain constant for all mutually exclusive and exhaustive time intervals if the underlying law is exponential but not for other common growth laws (e.g., logistic, Gompertz, power, general logistic). We propose a new growth metric specific to a particular growth law and show that it is capable of identifying the underlying growth model. The metric remains constant over different time intervals if the underlying law is true, while the extent of its variation reflects the departure of the assumed model from the true one. We propose a new estimator of the relative growth rate, which is more sensitive to the true underlying model than the existing one. The advantage of using this is that it can detect crucial intervals where the growth process is erratic and unusual. It may help experimental scientists to study more closely the effect of the parameters responsible for the growth of the organism/population under study.     

The influence of gibberellic acid and sulfur fertilization rate on growth and S-use efficiency of mustard (<Emphasis Type="Italic">Brassica juncea</Emphasis>)

Earlier research has shown that exogenous gibberellic acid (GA₃) application increases shoot growth, photosynthesis and soil nitrogen (N) utilisation in mustard (Brassica juncea L. Czern & Coss.). Mustard has a high sulfur (S) requirement. Its assimilatory pathway is well coordinated with N and dependent on photosynthesis. Thus, the higher photosynthate production and an efficient use of N with the use of GA₃ could result in an increase in S-use efficiency of the crop. The research was, therefore, carried out to study the effects of 10~M GA₃ spray on specific leaf area, plant dry mass, leaf carbon dioxide exchange rate (CER), plant growth rate (PGR), relative growth rate (RGR), net assimilation rate (NAR) and S-use efficiency (SUE) of mustard treated with 0, 100 or 200 mg S kg^–1 soil levels. Plants treated with 100~mg S kg^–1 soil and receiving GA₃ treatment showed increased specific leaf area and dry mass accumulation compared to the control. At 0~mg S kg^–1 soil, N and S concentrations were reduced. They increased with increasing S supply. GA₃ application significantly increased N and S concentrations further. A two-fold increase in SUE in GA₃-treated plants at 100~mg S kg^–1 soil was noted in comparison to the control. SUE was not increased under excess S conditions beyond 100~mg S kg^–1 soil. The increase in SUE was through increase in the growth, CER and use efficiency of N by the crop due to GA₃ application.     

Growth of Populus euramericana

Growth curves of successive leaves of Populus euramericana (Dode) Guinier 'Robusta' have been determined. With ample supply of water and nutrients the growth of a poplar shoot follows a fixed pattern: an initial logarithmic acceleration phase followed by a stationary phase in which leaves of equal size are produced at a constant rate. Analysis of growth curves of leaves enabled the growth curves of leaf primordia to be predicted. These primordial growth curves are compared to the indirectly determined growth curves of primordia by measuring the lengths of successive leaf primordia in the apex during the stationary phase of growth. The increase in length of successive leaves in the acceleration phase of growth continues for a longer period at high than at low irradiace. The relative growth rates of leaf primordia, leaves and internodes are discussed in terms of shoot growth and phyllotaxis.