A comparative analysis of karyotypes of three species of Macleaya—producers of a complex of isoquinoline alkaloids

Using a set of methods (C-banding, DAPI-staining, fluorescence hybridization in situ (FISH) with probes of 26S and 5S rDNA, and analysis of meiosis), the first comparative cytogenetic study of three species of Macleaya, producers of complex isoquinoline alkaloids, cordate Macleaya cordata (Willd.) R. Br. (2n = 20), small-fruited Macleaya microcarpa (Maxim.) Fedde (2n = 20) and Macleaya kewensis Turrill (2n = 20), was first carried out. On the basis of morphometric analysis, formulas of karyotypes were made for each species. Species ideograms for M. cordata, M. microcarpa, and M. kewensis were constructed taking into account the polymorphic variants of the C-banding patterns and indicating the location of 26S and 5S rDNA sites. A comparative study revealed that the karyotypes of M. microcarpa and M. kewensis have more in common with each other than with M. cordata. Analysis of meiotic chromosomes suggests of genetic stability of Macleaya genomes. The results of chromosome analysis were used to confirm the close relationship of Macleaya and to clarify their phylogenetic relationships.     

Effect of γ-Irradiation on Development of Lachrymator of Onion

A thermosensitive uracil requiring mutant of Bacillus subtilis Marburg 168 thy trp₂ ts42 was examined as to the colony forming ability at the permissive and nonpermissive temperatures. The viability of the mutant cells decreased rapidly at the restrictive temperature in the modified Woese’s (MW) medium. However, the cells retained viability when sodium succinate or potassium chloride was added to the medium at that temperature although uracil deficiency was unchanged. A little but significant incorporation of adenine-8-¹⁴C into RNA still continued even after the incorporation of N-acetyl-³H-d-glucosamine into acid insoluble fraction of the cells terminated in the MW medium at 48°C. Both incorporations as well as increase of absorbance were slowed down in the presence of sodium succinate at 48°C. This mutant, ts42, was more sensitive to deoxycholate (DOC) than the parent strain. The restoration of colony forming ability after the temperature shift back from 48 to 37°C was suppressed by the addition of DOC to the medium. However, the cell became resistant to DOC when uracil was added to the medium prior to the temperature shift.     

Mechanisms of action of the α-amylase of Micromonospora melanosporea

The -amylase of Micromonospora melanosporea was produced extracellularly during batch fermentation in a 5.0-1 fermentor. The absence of an organic nitrogen source in its growth medium facilitated subsequent purification of the enzyme by ammonium sulphate fractionation and two consecutive Superose-12 gel-filtration steps. The enzyme exhibited maxima for activity at pH 7.0 and 55° C and was 72% stable at pH 6.0–12.0 for 30 min at 40° C. It had a relative molecular mass of 45 000 and an isoelectric point at pH 7.6. The enzyme catalyses the conversion of starch to maltose (53%, w/w) as the predominant final end-product. Initial hydrolysis of this substrate, however, gave rise to the formation of maltooligosaccharides in the range maltotriose to maltohexaose. Maximum yields of these intermediate sugars accumulated to between 31 and 42% (w/w) as the reaction proceeded. The action of the M. melanosporea amylase on high concentrations of saccharides larger than maltotriose resulted in the formation of mainly maltose and maltotriose without concomitant glucose production. A combination of hydrolytic and transfer events is postulated to be responsible for this phenomenon and for the high maltose levels achieved. Correspondence to: C. T. Kelly     

Selection of optimal variants of Gō-like models of proteins through studies of stretching

The Gō-like models of proteins are constructed based on the knowledge of the native conformation. However, there are many possible choices of a Hamiltonian for which the ground state coincides with the native state. Here, we propose to use experimental data on protein stretching to determine what choices are most adequate physically. This criterion is motivated by the fact that stretching processes usually start with the native structure, in the vicinity of which the Gō-like models should work the best. Our selection procedure is applied to 62 different versions of the Gō model and is based on 28 proteins. We consider different potentials, contact maps, local stiffness energies, and energy scales—uniform and nonuniform. In the latter case, the strength of the nonuniformity was governed either by specificity or by properties related to positioning of the side groups. Among them is the simplest variant: uniform couplings with no i, i + 2 contacts. This choice also leads to good folding properties in most cases. We elucidate relationship between the local stiffness described by a potential which involves local chirality and the one which involves dihedral and bond angles. The latter stiffness improves folding but there is little difference between them when it comes to stretching.     

Chemistry of the “molecular trap” of protease-catalyzed splicing reaction of complementary segments of α-subunit of hemoglobin A

The complementary fragments of human Hb α, α_1–30, and α_31–141 are spliced together by V8 protease in the presence of 30%n-propanol to generate the full-length molecule (Hb α-semisynthetic reaction). Unlike the other protease-catalyzed protein/peptide splicing reactions of fragment complementing systems, the enzymic condensation of nonassociating segments of Hb α is facilitated by the organic cosolvent induced α-helical conformation of product acting as the “molecular trap” of the splicing reaction. The segments α_24–30 and α_31–40 are the shortest complementary segments that can be spliced by V8 protease. In the present study, the chemistry of the contiguous segment (product) α_24–40 has been manipulated by engineering the amino acid replacements to the positions α²⁷ and α³¹ to delineate the structural basis of the molecular trap. The location of Glu²⁷ and Arg³¹ residues in the contiguous segment α_24–40 (as well as in other larger segments) is ideal to generate (i, i+4) side-chain carboxylate-guanidino interaction in its α-helical conformation. The amino acid residue replacement studies have confirmed that the side chains at α²⁷ and α³¹ facilitate the semisynthetic reaction. The relative influence of the substitute at these sites on the splicing reaction depends on the chemical nature of the side chain and the location. The γ-carboxylate guanidino side-chain interaction appears to contribute up to a maximum of 85% of the thermodynamic stability of the molecular trap. The studies also demonstrate that the thermodynamic stability of the molecular trap is determined by two interdependent conformational aspects of the peptide. One is an amino acid-sequence-specific event that facilitates the induction of an α-helical conformation to the contiguous segment in the presence of organic cosolvent that imparts some amount of protease resistance to Glu³⁰-Arg³¹ peptide bond. The second structural aspect is a site-specific event, ani, i+4 side-chain interaction in the α-helical conformation of the peptide which imparts an additional thermodynamic stability to the molecular trap. The results suggest that conformationally driven “molecular traps” of protease-mediated ligation reactions of peptides could be designed into products to facilitate the modular assembly of peptides/proteins.     

Association of the subunits of the calcium-independent receptor of α-latrotoxin

CIRL-1 also called latrophilin 1 or CL belongs to the family of adhesion G protein-coupled receptors (GPCRs). As all members of adhesion GPSR family CIRL-1 consists of two heterologous subunits, extracellular hydrophilic p120 and heptahelical membrane protein p85. Both CIRL-1 subunits are encoded by one gene but as a result of intracellular proteolysis of precursor, mature receptor has two-subunit structure. It was also shown that a minor portion of the CIRL-1 receptor complexes dissociates, producing the soluble receptor ectodomain, and this dissociation is due to the second cleavage at the site between the site of primary proteolysis and the first transmembrane domain. Recently model of independent localization p120 and p85 on the cell surface was proposed. In this article we evaluated the amount of p120-p85 complex still presented on the cellular membrane and confirmed that on cell surface major amount of mature CIRL-1 presented as a p120-p85 subunit complex.     

Inhibition of colony-spreading activity of Staphylococcus aureus by secretion of δ-hemolysin

Staphylococcus aureus spreads on the surface of soft agar, a phenomenon we termed "colony spreading." Here, we found that S. aureus culture supernatant inhibited colony spreading. We purified δ-hemolysin (Hld, δ-toxin), a major protein secreted from S. aureus, as a compound that inhibits colony spreading. The culture supernatants of hld-disrupted mutants had 30-fold lower colony-spreading inhibitory activity than those of the parent strain. Furthermore, hld-disrupted mutants had higher colony-spreading ability than the parent strain. These results suggest that S. aureus negatively regulates colony spreading by secreting δ-hemolysin.     

Kinetics of renaturation and self-assembly of intermediates on the pathway of folding of the β2-subunit of Escherichia coli tryptophan-synthetase

The kinetics of renaturation of the β₂-subunit of Escherichia coli tryptophan-synthetase (l-serine hydrolyase (adding indole) E.C. 4.2.1.20) and those of its two proteolytic fragments F₁ and F₂ are studied and compared. Steps corresponding to the refolding of F₁, to the association of the folded F₁ and F₂ fragments, and to an isomerization of the associated protein are identified. These steps are ordered on the pathway of renaturation and some of their kinetic parameters are determined. This leads to a tentative kinetic model for the renaturation of nicked-β₂ starting from the denatured F₁ and F₂ fragments.The step corresponding to the refolding of the F₁ domain, as well as that corresponding to the last rate-limiting isomerization leading to the native protein, is shown to be the same in the refolding of the entire, uncleaved β₂-protein. It is concluded that the refolded F₁ fragment corresponds to a folding intermediate on the pathway of renaturation of the β₂-subunit.     

Within-generation and transgenerational plasticity in growth and regeneration of a subordinate annual grass in a rainfall experiment

Precipitation changes may induce shifts in plant species or life form dominance in ecosystems, making some previously subordinate species abundant. The plasticity of certain plant functional traits of these expanding subordinate species may be one possible mechanism behind their success. In this study, we tested if the subordinate winter annual grass Secale sylvestre shows plasticity in growth and reproduction in response to altered environment associated with field-scale rainfall manipulations (severe drought, moderate drought, and watering) in a semiarid grassland, and whether the maternal environment influences offspring germination or growth in a subsequent pot experiment. Compared to control plots, S. sylvestre plants grew 38% taller, and produced 32% more seeds in severe drought plots, while plants in watered plots were 17% shorter, and had 22% less seeds. Seed mass was greatest in severe drought plots. Plants growing in drought plots had offspring with enhanced juvenile shoot growth compared to the progeny whose mother plants grew in watered plots. These responses are most likely explained by the decreased cover of previously dominant perennial grasses in severe drought plots, which resulted in wetter soil compared to control and watered plots during the peak growth of S. sylvestre. We conclude that the plasticity of this subordinate annual species in response to changing environment may help to gain dominance with recurring droughts that suppress perennial grasses. Our results highlight that exploring both within-generation and transgenerational plasticity of subordinate species may lead to a better prediction of changes in plant species dominance under climate change.

     

四种不同生活型植物幼苗对喀斯特生境干旱的生理生态适应性

喀斯特石漠化是我国西南喀斯特地区最严重的生态环境问题, 生境干旱是限制该地区植物生长的主要因素之一, 掌握喀斯特植被不同演替阶段不同生活型植物对干旱胁迫的适应策略有助于提高植被恢复的成功率。通过人工模拟4种干旱强度, 测定叶片水势、气体交换、叶绿素荧光、光合色素含量、渗透调节物质浓度、抗氧化酶活性以及生物量, 研究了喀斯特地区4种不同生活型植物幼苗对干旱胁迫的适应策略。这4种植物为常绿灌木火棘(Pyracantha fortuneana)、落叶灌木小果蔷薇(Rosa cymosa)、常绿乔木猴樟(Cinnamomum bodinieri)和落叶乔木圆果化香树(Platycarya longipes)。结果表明: 随着干旱程度的加深, 4种植物幼苗的叶片水势、光合能力、叶绿素含量、生物量增长、叶重比(LMR)、叶面积比(LAR)和比叶面积(SLA)逐渐下降, 而热耗散(NPQ)、类胡萝卜素与叶绿素含量比值、丙二醛含量和根重比(RMR)逐渐上升; 圆果化香树和猴樟的水分利用效率(A_n/g_s)、渗透调节物质浓度和抗氧化酶活性呈先升高后降低的趋势, 而火棘和小果蔷薇的A_n/g_s、脯氨酸含量和超氧化物歧化酶活性呈上升趋势。严重干旱下, 火棘和小果蔷薇幼苗的叶片水势和叶绿素含量下降较少, 具有较高的光合能力和生物量增长, 这主要是由于它们具有较低的SLA和LAR、较高的NPQ和A_n/g_s以及较高的渗透调节能力和抗氧化保护能力。中度干旱下, 猴樟幼苗叶片水势下降很少, LMR和LAR也较高, 脯氨酸含量和抗氧化酶活性非常高。但在严重干旱下, 其叶片水势、LMR、LAR和生物量增长大幅度下降, 最大光化学效率和光合速率也非常低, 渗透调节能力与抗氧化酶活性大幅度下降至正常水平以下。水分好的条件下, 圆果化香树幼苗具有较高的RMR以吸收充足的水分, 具有较高的LAR和叶绿素含量, 保证了生物量的大量积累。然而, 干旱胁迫致使其生物量大幅度下降, 主要是由于LMR、LAR、气体交换和叶绿素含量的大量下降以减少蒸腾面积、水分散失和对光能的吸收。研究结果表明, 火棘、小果蔷薇和猴樟幼苗主要采用耐旱策略, 其中猴樟抗严重干旱的能力较弱; 圆果化香树幼苗对干旱胁迫更为敏感, 主要采取避旱策略。     

The type of competition modulates the ecophysiological response of grassland species to elevated CO2 and drought

The effects of elevated CO₂ and drought on ecophysiological parameters in grassland species have been examined, but few studies have investigated the effect of competition on those parameters under climate change conditions. The objective of this study was to determine the effect of elevated CO₂ and drought on the response of plant water relations, gas exchange, chlorophyll a fluorescence and aboveground biomass in four grassland species, as well as to assess whether the type of competition modulates that response. Elevated CO₂ in well‐watered conditions increased aboveground biomass by augmenting CO₂ assimilation. Drought reduced biomass by reducing CO₂ assimilation rate via stomatal limitation and, when drought was more severe, also non‐stomatal limitation. When plants were grown under the combined conditions of elevated CO₂ and drought, drought limitation observed under ambient CO₂ was reduced, permitting higher CO₂ assimilation and consequently reducing the observed decrease in aboveground biomass. The response to climate change was species‐specific and dependent on the type of competition. Thus, the response to elevated CO₂ in well‐watered grasses was higher in monoculture than in mixture, while it was higher in mixture compared to monoculture for forbs. On the other hand, forbs were more affected than grasses by drought in monoculture, while in mixture the negative effect of drought was higher in grasses than in forbs, due to a lower capacity to acquire water and mineral nutrients. These differences in species‐level growth responses to CO₂ and drought may lead to changes in the composition and biodiversity of the grassland plant community in future climate conditions.     

Shade tolerance and herbivory are associated with RGR of tree species via different functional traits

• Relative growth rate (RGR) plays an important role in plant adaptation to the light environment through the growth potential/survival trade‐off. RGR is a complex trait with physiological and biomass allocation components. It has been argued that herbivory may influence the evolution of plant strategies to cope with the light environment, but little is known about the relation between susceptibility to herbivores and growth‐related functional traits.
• Here, we examined in 11 evergreen tree species from a temperate rainforest the association between growth‐related functional traits and (i) species’ shade‐tolerance, and (ii) herbivory rate in the field. We aimed at elucidating the differential linkage of shade and herbivory with RGR via growth‐related functional traits.
• We found that RGR was associated negatively with shade‐tolerance and positively with herbivory rate. However, herbivory rate and shade‐tolerance were not significantly related. RGR was determined mainly by photosynthetic rate (A_max) and specific leaf area (SLA). Results suggest that shade tolerance and herbivore resistance do not covary with the same functional traits. Whereas shade‐tolerance was strongly related to A_max and to a lesser extent to leaf mass ratio (LMR) and dark respiration (R_d), herbivory rate was closely related to allocation traits (SLA and LMR) and slightly associated with protein content.
• The effects of low light on RGR would be mediated by A_max, while the effects of herbivory on RGR would be mediated by SLA. Our findings suggest that shade and herbivores may differentially contribute to shape RGR of tree species through their effects on different resource‐uptake functional traits.

     

Close relationship between leaf life span and seedling relative growth rate in temperate hardwood species

The life span of resource-acquiring organs (leaves, shoots, fine roots) is closely associated with species successional position and environmental resource availability. We examined to what extent leaf life span is related to inter- and intraspecific variation in seedling relative growth rate (RGR). We examined relationships between relative growth rate in mass (RGR_M) or height (RGR_H) and leaf life span, together with classical RGR_M components [net assimilation rate (NAR), specific leaf area (SLA), leaf weight ratio (LWR), and leaf area ratio (LAR)] for seedlings of five hardwood species of different successional position across a wide range of environmental resource availability, including the presence or absence of leaf litter in shaded forest understory, small canopy gaps, and large canopy gaps. Both SLA and LAR were negatively correlated with RGR_M along the environmental gradient for all species. However, positive correlations were observed among species within microsites, indicating that these two components cannot consistently explain the variation in RGR_M. Both NAR and LWR affect interspecific, but not intraspecific, variation in RGR_M. Leaf life span was negatively correlated with either RGR_M or RGR_H in both inter- and intraspecific comparisons. Species with short-lived, physiologically active leaves have high growth rates, particularly in resource-rich environments. Consequently, leaf life span is a good predictor of seedling RGR. Leaf life span affects plant performance and has a strong and consistent effect on tree seedling growth, even among contrasting environments.     

Responses of temperate woody seedlings to shade and drought: do trade-offs limit potential niche differentiation?

Diversity in seedling responses to combined shade and drought can drive species niche differences, and thus natural forest and scrub establishment dynamics and diversity. However, inherent trade-offs between shade tolerance and drought tolerance, as hypothesized in the literature, would constrain potential niche differentiation. For thirteen species of European trees and shrubs the impacts were determined of moderate and extreme drought on the growth and survival of first-year seedlings in a given soil volume, in irradiances in the range typical for temperate forest and scrub understories (3% daylight) and large gaps (30% daylight). Pots were watered differentially each second day to equalize soil water content across species and irradiances. Comparisons within and across species supported independent tolerances of shade and drought rather than trade-offs. For all species, drought reduced relative growth rate in dry mass by the same proportion in 3% daylight and in 30% daylight. Consequently, drought generally reduced final dry mass significantly more strongly in 30% daylight than in 3% daylight. Extreme drought led to earlier mortality in 30% daylight than in 3% daylight for nine of the eleven species tested, to earlier mortality in 3% daylight for one species, and to equal mortality rate in both irradiances for one species. For each species, growth-based shade tolerance was quantified as the ratio of absolute growth in low irradiance to that in high irradiance, and growth-based drought tolerance as the ratio of absolute growth in low water supply to that in high water supply. Across species, growth-based shade tolerance varied ≈9-fold, and growth-based drought tolerance ≈2-fold; species’ tolerances correlated respectively with indices of field establishment in shade and drought. Growth-based drought tolerance correlated with survival time in extreme drought. Experimentally quantified shade and drought tolerances varied independently for the 13 species tested, indicating the potential for extensive species niche differentiation in combinations of irradiance and water supply.     

Water-use efficiency and whole-plant performance of nine tropical tree species at two sites with contrasting water availability in Panama

Across their natural distributions, tropical tree species are regularly exposed to seasonal droughts of varying intensities. Their ability to tolerate drought stress plays a vital role in determining growth and mortality rates, as well as shaping the functional composition of tropical forests. In order to assess the ability of species to acclimate to contrasting levels of drought stress, physiological and structural traits involved in drought adaptation—wood C isotope discrimination (δ¹³C), wood specific gravity, and wood C content—of 2-year-old saplings of nine tropical tree species were evaluated in common garden experiments at two study sites in Panama with contrasting seasonality. We assessed co-variation in wood traits with relative growth rates (RGR_BD), aboveground biomass, and basal diameter and the plasticity of wood traits across study sites. Overall, species responded to lower water availability by increasing intrinsic water-use efficiency, i.e., less negative wood δ¹³C, but did not exhibit a uniform, directional response for wood specific gravity or wood C content. Trait plasticity for all wood traits was independent of RGR_BD and tree size. We found that the adaptive value of intrinsic water-use efficiency varied with water availability. Intrinsic water-use efficiency increased with decreasing RGR_BD at the more seasonal site, facilitating higher survival of slower growing species. Conversely, intrinsic water-use efficiency increased with tree size at the less seasonal site, which conferred a competitive advantage to larger individuals at the cost of greater susceptibility to drought-induced mortality. Our results illustrate that acclimation to water availability has negligible impacts on tree growth over short periods, but eventually could favor slow-growing species with conservative water-use strategies in tropical regions experiencing increasingly frequent and severe droughts.     

Comparative ecophysiological responses to drought of two shrub and four tree species from karst habitats of southwestern China

Drought stress is one of the most important factors in limiting the survival and growth of plants in the harsh karst habitats of southwestern China, especially at the seedling establishment stage. The ecophysiological response to drought stress of native plants with different growth forms is useful for re-vegetation programs. Two shrub and four tree species were studied, including Pyracantha fortuneana (evergreen shrub), Rosa cymosa (deciduous shrub), Cinnamomum bodinieri (evergreen tree), and other three deciduous trees, Broussonetia papyrifera, Platycarya longipes, and Pteroceltis tatarinowii. The seedlings were randomly assigned to four drought treatments, i.e., well-watered, mild drought stress, moderate drought stress, and severe drought stress. Leaf water relations, gas exchange, chlorophyll fluorescence, and growth of the seedlings were investigated. Under severe drought stress, the two shrubs with low leaf area ratio (LAR) maintained higher water status, higher photosynthetic capacity, and larger percent biomass increase than the most of the trees. The two shrubs also had lower specific leaf area, greater intrinsic water use efficiency, and thermal dissipation than the trees. This suggested that the two shrubs had high tolerance to severe drought and were suitable for re-vegetation in harsh habitats. The evergreen C. bodinieri exhibited higher leaf mass ratio (LMR) and LAR than the deciduous species under mild and moderate stress. However, the low maximum quantum efficiency of PSII photochemistry (F _v/F _m) and net assimilation rate, and the sharp decreases of water potential, LMR, LAR, and biomass under severe stress indicated C. bodinieri’s weak tolerance to severe drought. In response to drought stress, the three deciduous trees revealed sharp reductions of biomass due to the large drought-induced decreases of gas exchange, LAR, and LMR. Under drought conditions, the deciduous trees minimized water loss by stomatal closure and by reducing transpiration leaf area and light harvesting through shedding leaves. This suggested that the three deciduous trees were more sensitive to water availability than the shrubs and used avoidance strategies against drought stress. However, the better growth performance of the deciduous trees than that of the shrubs under favorable conditions suggested that deciduous trees could be suitable for habitats with mild and temporary drought stress.     

Fungal Symbionts Alter Plant Drought Response

Grassland productivity is often primarily limited by water availability, and therefore, grasslands may be especially sensitive to climate change. Fungal symbionts can mediate plant drought response by enhancing drought tolerance and avoidance, but these effects have not been quantified across grass species. We performed a factorial meta-analysis of previously published studies to determine how arbuscular mycorrhizal (AM) fungi and endophytic fungal symbionts affect growth of grasses under drought. We then examined how the effect of fungal symbionts on plant growth was influenced by biotic (plant photosynthetic pathway) and abiotic (level of drought) factors. We also measured the phylogenetic signal of fungal symbionts on grass growth under control and drought conditions. Under drought conditions, grasses colonized by AM fungi grew larger than those without mycorrhizal symbionts. The increased growth of grasses conferred from fungal symbionts was greatest at the lowest soil moisture levels. Furthermore, under both drought and control conditions, C3 grasses colonized by AM fungi grew larger than C3 grasses without symbionts, but the biomass of C4 grasses was not affected by AM fungi. Endophytes did not increase plant biomass overall under any treatment. However, there was a phylogenetically conserved increase in plant biomass in grasses colonized by endophytes. Grasses and their fungal symbionts seem to interact within a context-dependent symbiosis, varying with biotic and abiotic conditions. Because plant–fungal symbioses significantly alter plant drought response, including these responses could improve our ability to predict grassland functioning under global change.     

Effects of extreme drought on specific leaf area of grassland species: A meta‐analysis of experimental studies in temperate and sub‐Mediterranean systems

Here, we conducted a meta‐analysis of experimental drought manipulation studies using rainout shelters in five sites of natural grassland ecosystems of Europe. The single studies assess the effects of extreme drought on the intraspecific variation of the specific leaf area (SLA), a proxy of plant growth. We evaluate and compare the effect size of the SLA response for the functional groups of forbs and grasses in temperate and sub‐Mediterranean systems. We hypothesized that the functional groups of grasses and forbs from temperate grassland systems have different strategies in short‐term drought response, measured as adjustment of SLA, with SLA‐reduction in grasses and SLA‐maintenance in forbs. Second, we hypothesized that grasses and forbs from sub‐Mediterranean systems do not differ in their drought response as both groups maintain their SLA. We found a significant decrease of SLA in grasses of the temperate systems in response to drought while SLA of forbs showed no significant response. Lower SLA is associated with enhanced water‐use efficiency under water stress and thus can be seen as a strategy of phenotypic adjustment. By contrast, in the sub‐Mediterranean systems, grasses significantly increased their SLA in the drought treatment. This result points towards a better growth performance of these grasses, which is most likely related to their strategy to allocate resources to belowground parts. The observed SLA reduction of forbs is most likely a direct drought response given that competitive effect of grasses is unlikely due to the scanty vegetation cover. We point out that phenotypic adjustment is an important driver of short‐term functional plant response to climatic extremes such as drought. Differential reactions of functional groups have to be interpreted against the background of the group's evolutionary configuration that can differ between climatic zones.