Size‐dependent resource allocation and sex allocation in herbaceous perennial plants

Individuals within a population often differ considerably in size or resource status as a result of environmental variation. In these circumstances natural selection would favour organisms not with a single, genetically determined allocation, but with a genetically determined allocation rule specifying allocation in relation to size or environment. Based on a graphical analysis of a simple evolutionarily stable strategy (ESS) model for herbaceous perennial plants, we aim to determine how cosexual plants within a population should simultaneously adjust their reproductive allocation and sex allocation to their size. We find that if female fitness gain is a linear function of resource investment, then a fixed amount of resources should be allocated to male function, and to post‐breeding survival as well, for individuals above a certain size threshold. The ESS resource allocation to male function, female function, and post‐breeding survival positively correlate if both male and female fitness gains are a saturating function of resource investment. Plants smaller than the size threshold are expected to be either nonreproductive or functionally male only.     

The rates of shoot and root growth in intact plants of pea mutants in leaf morphology

Isogenic lines of pea (Pisum sativum L.) with the genetically determined changes in leaf morphology, afila (af) and tendril-less (tl), were used to study the relationship between shoot and root growth rates. The time-course of shoot and root growth was followed during the pre-floral period in the intact plants grown under similar conditions. The af mutation produced afila leaves without leaflets, whereas in the case of the tl mutations, tendrils were substituted with leaflets, and acacia-like leaves were developed. Due to the changes in leaf morphology caused by these mutations, pea genotypes differed in leaf area: starting from day 7, the leaf area was lower in the af plants and larger in the tl plants as compared to the wild-type plants. Such divergence was amplified in the course of plant development and reached its maximum immediately before the transition to flowering. Plants of isogenic lines did not notably differ in stem surface areas. In spite of significant difference in total leaf area, the wild type and tl plants did not differ in leaf dry weight. Starting from leaf 9, the af plants lagged behind two leaflet-bearing genotypes (wild type and tl) in leaf dry weight, whereas stem dry weight was similar in the wild type and tl forms and slightly lower in the af plants. Root dry weights were practically similar in the wild type and tl plants until flowering. The reduction of leaf area in the af plants drastically reduced root dry weight. In other words, the latter index was related to the total weight and total area of leaves and stems. The correlation analysis demonstrated an extremely low relationship between leaf and stem area and dry weight and those of roots early in plant development (when plants develop five to seven leaves). Later, immediately before flowering (nine to eleven leaves), root weight was positively related to leaf weight and area; however, stem area and root weight did not correlate. Thus, in three genotypes (wild type, af, and tl), at the end of their vegetative growth phase, leaf and root biomass accumulated in proportion, independently of leaf area expansion.     

Leaf damage induces twining in a climbing plant

Successful climbing by vines not only prevents shading by neighbouring vegetation, but also may place the vines beyond ground herbivores. Here we tested the hypothesis that herbivory might enhance climbing in a vine species, and that such induced climbing should be greater in the shade. We assessed field herbivory in climbing and prostrate ramets of the twining vine Convolvulus arvensis. We evaluated plant climbing after mechanical damage in a glasshouse under both sun and shade conditions, and determined whether control and damaged plants differed in growth rate or photosynthetic capacity. Plants experienced greater herbivory when growing prostrate than when climbing onto companion plants, in both an open habitat and a shaded understorey. Experimental plants increased their twining rate on a stake after suffering leaf damage, in both high- and low-light conditions, and this induced climbing was not coupled to an increase in growth rate. Increased photosynthesis was associated with enhanced twining rate only in the shade. Herbivory may be an ecological factor promoting the evolution of a climbing habit in plants.     

Steady-state nutrition and growth responses of Betula pendula to different relative supply rates of copper

In a series of experiments on the growth and nutrition of copper-limited birch (Betula pendula Roth) plants, growth was controlled by the relative addition rate of copper, R_Cu (d^–1). This was 0·05, 0·10, 0·15 or 0·20 d^–1 with free access to all other nutrients. An additional treatment provided free access to all nutrients. The pH in the nutrient solution was ≈ 4·5 and conductivity was 100 μS cm^–1. At steady-state growth, there was a linear relationship between the relative growth rate, R_G, and R_Cu. The [Cu] of the plants ranged from 2·4 to 2·7 μg g^–1 dry mass (DM) in all treatments with limiting R_Cu and was ≈ 28 μg g^–1 in the free access treatment. The plants showed specific copper deficiency symptoms at limitation. Total non-structural carbohydrate concentrations and the fraction of plant DM partitioned to roots was much less at copper limitation than at free access. The uptake rate of copper per unit root growth rate, dCu/dW_r (μmol g^–1 root DM) was unaffected by the copper supply. Low rates of plant growth at copper limitation were associated with high values of specific leaf area (SLA; 47 m² kg^–1) and leaf area ratio (LAR; 28 m² kg^–1 plant DM) but lower values of net assimilation rate (NAR; 2·5 kg m^–2 leaf DM d^–1) than were found at free access, 28 m² kg^–1 (SLA), 17 m² kg^–1 DM (LAR) and 14 kg m^–2 leaf DM d^–1 (NAR), respectively. It is not obvious from the present data how the growth response can help alleviate copper limitation in the field.     

北方地区藤本类忍冬叶表皮结构及其生态适应性比较研究

利用光镜和扫描电镜观察了8种在北京地区引种栽培成功的藤本类忍冬的叶表皮形态,观察指标包括气孔器、表皮毛、表皮细胞特征等.结合其在北京的栽培状况,发现叶片表皮形态和解剖结构与生态适应性之间有很强的相关性.自然分布广、适应性强的种在叶表皮形态上表现出气孔密度大、表皮细胞小、被毛或叶革质等特征.金银花、红白忍冬、淡红忍冬是8种忍冬中适应性最强的,具有推广应用价值.本研究为藤本类忍冬在北方地区推广应用提供了理论基础.     

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.     

Female-biased sex allocation in relation to growth rate of fruit in Erythronium japonicum

Using four populations of the liliaceous perennial Erythronium japonicum, I examined the hypothesis that sex allocation will be female-biased if the duration of sink-limited growth of fruits, during which fruits grow exponentially, is long. I found that all marked fruits in each population had a period of sink-limited growth. Among the four populations, the mean length of sink-limited growth increased, and the mean dry mass ratio of the sum of the corolla and androecium/fruit decreased, in a consistent order. Thus, plants in populations where the duration of sink-limited growth was long allocated relatively more of their resources to their female functions. This result was consistent with the above hypothesis. Received: 21 March 1998 / Accepted: 27 August 1998     

水位和氮浓度对三江藨草幼苗生长和生物量分配的影响

以莫莫格国家级自然保护区常见植物三江藨草(Scirpus nipponicus)为研究对象,设置低(5 cm)、中(35 cm)、高(65 cm) 3个水位和低(4 mmol·L-1)、中(8 mmol·L-1)、高(12mmol·L-1) 3个氮浓度交互的室内控制实验,探究不同水位和氮浓度对湿地植物三江藨草幼苗生长及生物量分配的影响。结果表明:水位对三江藨草幼苗生长、生物量及其分配均产生显著影响(P<0.05),随着水位的升高,三江藨草株高增加,分株数、球茎数及根生物量降低,根茎、球茎、地下、地上和总生物量均呈先增加后降低的趋势;植株地上生物量分配增加,地下(包括根和球茎)生物量分配降低;氮浓度仅对植株株高、球茎数以及地下与地上部分的生物量分配有显著影响(P<0.05),对分株数及生物量的累积均无显著影响(P>0.05);综合三江藨草幼苗的生长特征和生物量累积,认为其生长的最适宜水位为35 cm;且低水位有利于植株对氮的吸收,高水位和高氮浓度限制植株的生长。     

Comparison of biomass allocation in ectomycorrhizal and nonmycorrhizal Douglas fir seedlings of similar nutrition and overall size

Biomass allocation in 6-month-old ectomycorrhizal Douglas fir seedlings was compared to that in nonmycorrhizal seedlings of the same age, nutrient status and total biomass. Seedlings colonized by Rhizopogon vinicolor had the same distribution of biomass between roots, stems and needles, but only 56% of the total length of roots (including mycorrhizal branches) compared to nonmycorrhizal seedlings. Laccaria laccata had no effect on distribution of biomass or root length of seedlings. The results for Rhizopogon provide direct evidence that the process of ectomycorrhizal colonization can significantly affect plant biomass allocation by one or more mechanisms not directly related to altered nutrition or overall plant size.     

Regeneration,colonisation and growth rates of allofragments in four common stream plants

Colonisation by stream plants occurs to a large extent from simple stem fragments. Allofragments are stem fragments formed by mechanical breakage. We studied regeneration, colonisation, and growth rates in four common stream plants: Elodea canadensis Michx., Myriophyllum spicatum L., Potamogeton perfoliatus L. and Ranunculus baudotii x pseudofluitans. The objectives of this study were to determine (1) if shoots with an apical tip have higher regeneration (growth of new shoots and rhizomes from allofragments) and colonisation (root attachment in sediment) abilities and higher relative growth rates (RGR) than shoots without an apical tip, and (2) if fragment size correlates with regeneration and colonisation abilities and with RGR of fragments. For all species, over 60% of fragments regenerated new shoots and colonised. Apical shoots and larger fragments generally had higher regeneration and colonisation abilities and higher RGR. Relative growth rate for E. canadensis and M. spicatum was between 0.06 and 0.09 d⁻¹ whereas it was about half this rate for Ranunculus and P. perfoliatus (0.02–0.04 d⁻¹).     

Special symposium: In vitro plant recalcitrance recalcitrance of woody and herbaceous perennial plants: Dealing with genetic predeterminism

Summary As a general, long-lived perennial plants probably present the most challenging obstecles to the researcher, breeder or propagator utilizing microculture as a tool. These challenges appear during all stages of the microculture process, but are probably most resplendent during the stabilization phase. What may be particularly frustrating is that much of this ‘recalcitrance’ is genetically driven and is thus difficult to control by environmental and nutritional manipulations in microculture. Perennials have complex seasonal cycles and life cycles, which complicate control of their growth in microculture. As shoot cultures have provided useful tools for overcoming these limitations, the inability to establish stabilized shoot cultures is a major form of recalcitrance. Plants having seasonal growth dynamics dominated by strong episodic or determinant shoot growth are some of the most recalcitrant species because stabilized shoot cultures cannot be readily generated. In some cases, episodic growth may be tied closely to phase state and can thus be controlled by manipulating phase; nevertheless, adequate controls have not been identified for many problematic plants. Another trait contributing to recalcitrance of perennials is the relatively slow growth rate in microculture. Slow growth complicates such procedures as selection of transformed tissues. The high phenolic content of many perennial tissues can interfere with the efficacy of transgenic traits such as β-glucuronidase. Developmentally determined growth characteristics such as plagiotropism may persist through all stages of microculture and complicate the recovery of commercially useful micropropagules. Although some technical approaches can occasionally circumvent immediate microculture limitations, general solutions await the development of a deeper understanding of physiological bases of such genetically predetermined phenomena.     

Effects of ramet clipping and nutrient availability on growth and biomass allocation of yellow nutsedge

A glasshouse experiment was conducted to examine how the interactions of nutrient availability and partial ramet clipping affect growth, reproduction and biomass allocation of Cyperus esculentus, an invasive sedge. The plants sprouting from tubers were grown at low and high nutrient levels, and were subject either to no clipping, one, two or three clippings, with each clipping cutting half of the existing ramets at soil level. Our results show that nutrient availability and clipping frequency tended to independently affect most of growth, reproduction and biomass allocation parameters of Cyperus esculentus examined in the present study. Increased supply of nutrients led to an increase in plant productivity and its associated traits. All of the traits, except for the number of ramets, displayed a decreasing pattern with increasing clipping frequency, indicating that Cyperus esculentus had undercompensatory responses to ramet clipping. It is likely that the patterns of plants response to clipping are species specific, and depend on morphological characters of species. Its susceptibility to ramet clipping can offer opportunities for controlling this invasive species through mechanical methods such as mowing. Clipping had little effects on biomass allocation; however, root weight fraction increased with increasing clipping frequency. While nutrient availability and clipping frequency had no influence on leaf carbon concentration at harvest, both of them increased leaf nitrogen concentration, and hence reduced leaf C/N ratio.     

Crown development in a pioneer tree, Rhus trichocarpa, in relation to the structure and growth of individual branches

Based on an allometric reconstruction, the structure and biomass-allocation patterns of branches and current-year shoots were investigated in branches of various heights in the pioneer tree Rhus trichocarpa, to evaluate how crown development is achieved and limited in association with height. Path analysis was conducted to explore the effects of light availability, basal height and size of individual branches on branch structure and growth. Branch angle was affected by basal height, whereas branch mass was influenced primarily by light availability. This result suggests that branch structure is strongly constrained by basal height, and that trees mediate such constraints under different light environments. Previous-year leaf area and light availability showed positive effects on current-year stem mass. In contrast, branch basal height and mass negatively affected current-year stem mass. Moreover, the length of stems of a given diameter decreased with increasing branch height. Therefore the cost of biomass investment for a unit growth in length is greater for branches of larger size and at upper positions. Vertical growth rate in length decreased with increasing height. Height-dependent changes in stem allometry and angle influenced the reduction in vertical growth rate to a similar degree.     

Relationships among Rhizosphere Oxygen Deficiency,Root Restriction,Photosynthesis, and Growth in Baldcypress (Taxodium Distichum L.) Seedlings

Seedlings of baldcypress (Taxodium distichum L.) grown in sealed containers containing nutrient solution were subjected to root-zone oxygen deficiency, physical restriction, and the combined stresses in a greenhouse. After six weeks of treatments (Phase I), half of the plants were harvested. The remaining half were allowed to continue (Phase II) under various treatments except plants that had restricted roots were freed thus allowing free expansion of roots into the nutrient solution. Oxygen deficiency and root physical restriction inhibited plant gas exchange parameters. Net photosynthetic rate (PN) was significantly higher in aerated unrestricted root (AUR) plants than in aerated root restricted (AR) plants and in anaerobic root unrestricted (FUR) plants than in anaerobic root restricted (FR) plants. After Phase I, FUR plants' shoot and root biomasses were 57.0 and 30.6 % lower than those of AUR plants, and AUR plants showed 3.3 and 3.8 times greater shoot and root biomasses than the AR plants, respectively. During Phase II, PN recovered rapidly in plants under aerated conditions, but not in plants under anaerobic conditions. The removal of physical root restriction under both aerated and anaerobic conditions resulted in rapid shoot and root growth in seedlings. Hence, root restriction or root-zone anaerobiosis, reductions in plant gas exchange, and biomass production in baldcypress were closely interrelated. In addition, root release from restriction was related to the regain of photosynthetic activity and biomass growth. The results support the previously proposed source-sink feed-back inhibition of photosynthesis in plants subjected to root-zone oxygen deficiency or physical restriction.     

Evolution of resource allocation between growth and reproduction in animals with indeterminate growth

We review the recent theoretical developments explaining the evolution of age-schedules of reproduction in animals with indeterminate growth. Indeterminate growth, i.e. growth that continues past maturation and may continue until the end of life, is characteristic for a large number of invertebrate taxa (e.g. clams, cladocerans and crayfish) and ‘lower’ vertebrate taxa (e.g. fish, amphibians, lizards and snakes). Many plants also exhibit indeterminate growth, and we liberally include studies focused on plants when they can be interpreted in terms of animal life histories. We focus on different measures used to determine the fittest life histories, on indeterminate growth as a problem of resource allocation and on the effects of environment to the evolution of the resource allocation schemes.