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Summary: The molecular mechanisms controlling underwater elongation are based extensively on studies on internode elongation in the monocot rice (Oryza sativa) and petiole elongation in Rumex rosette species. Here, we characterize underwater growth in the dicot Nasturtium officinale (watercress), a wild species of the Brassicaceae family, in which submergence enhances stem elongation and suppresses petiole growth.We used a genome‐wide transcriptome analysis to identify the molecular mechanisms underlying the observed antithetical growth responses. Though submergence caused a substantial reconfiguration of the petiole and stem transcriptome, only little qualitative differences were observed between both tissues. A core submergence response included hormonal regulation and metabolic readjustment for energy conservation, whereas tissue‐specific responses were associated with defense, photosynthesis, and cell wall polysaccharides.Transcriptomic and physiological characterization suggested that the established ethylene, abscisic acid (ABA), and GA growth regulatory module for underwater elongation could not fully explain underwater growth in watercress.Petiole growth suppression is likely attributed to a cell cycle arrest. Underwater stem elongation is driven by an early decline in ABA and is not primarily mediated by ethylene or GA. An enhanced stem elongation observed in the night period was not linked to hypoxia and suggests an involvement of circadian regulation. See also the Editorial on this article by Sasidharan et al., 229: 5–7. [ABSTRACT FROM AUTHOR]

Summary: Climate warming may stimulate growth and reproduction in cold‐adapted plants, but also reduce their performance due to warming‐induced drought limitation. We tested this theory using a unique experiment with the alpine forb Rumex alpinus.We examined how climate warming over the past four decades affected its annual rhizome growth, leaf production and flowering, and whether responses varied between alpine, subalpine and montane populations.Before the period of accelerated warming in the 1970s and 1980s, the primary limitation on growth had been cold temperatures and short growing seasons. Increased summer temperatures in the 1990s and 2000s enhanced rhizome growth and leaf production, but not flowering. Alpine and subalpine plants profit more than montane plants, currently producing three times longer annual rhizome increments and twice as many leaves as 40 yr ago, and achieving nearly the same values as montane plants. During the warmest 2005–2015 period, growth became contingent on summer precipitation and began to decrease across all populations, likely due to an increasing water shortage in dense monospecific stands. Warming releases plants from cold limitations but induces water shortage.Rumex alpinus exceeds its thermal optimum and becomes water‐limited as the climate warms. Our results suggest that warming‐induced responses in alpine plants will not be one‐sided shifts to higher growth and reproduction, but rather multidimensional and spatiotemporally variable. [ABSTRACT FROM AUTHOR]

Summary: It has long been known that more pollen grains often arrive on stigmas than there are ovules to fertilize, resulting in pollen competition. Moreover, this competition among pollen grains (gametophytes) depends, in part, on their extensive haploid gene expression. Here I review how this leads to a variety of phenomena in dioecious plants of interest to evolutionary biologists. For example, pollen competition can lead to extreme female‐biased sex ratios. In addition, gene expression by individual pollen grains can slow mutation accumulation and degeneration of the Y chromosome. Lastly, I review work on how the haploid selection resulting from pollen competition has been proposed to influence which alleles are linked to the Y chromosome, and some recent empirical evidence in support of this theory. [ABSTRACT FROM AUTHOR]

Summary [ABSTRACT FROM AUTHOR]

• Plants can respond to their environment by morphological plasticity. Generally, the potential benefits of adaptive plastic responses are beyond doubt under predictable environmental changes. However, the net benefits may be less straightforward when plants encounter temporal stresses, such as flooding in river flood plains. • Here, we tested whether the balance of costs and benefits associated with flooding-induced shoot elongation depends on the flooding regime, by subjecting Rumex palustris plants with different elongation capacity to submergence of different frequency and duration. • Our results showed that reaching the surface by shoot elongation is associated with fitness benefits, as under less frequent, but longer, flooding episodes plants emerging above the floodwater had greater biomass production than plants that were kept below the surface. As we predicted, slow-elongating plants had clear advantages over fast-elongating ones if submergence was frequent but of short duration, indicating that elongation also incurs costs. • Our data suggest that high costs select for weak plasticity under frequent environmental change. In contrast to our predictions, however, fast-elongating plants did not have an overall advantage over slow-elongating plants when floods lasted longer. This indicates that the delicate balance between benefits and costs of flooding-induced elongation depends on the specific characteristics of the flooding regime. [ABSTRACT FROM AUTHOR]

• Earlier work on the submergence-tolerant species Rumex palustris revealed that leaf anatomical and morphological changes induced by submergence enhance underwater gas exchange considerably. Here, the hypothesis is tested that these plastic responses are typical properties of submergence-tolerant species. • Submergence-induced plasticity in leaf mass area (LMA) and leaf, cell wall and cuticle thickness was investigated in nine plant species differing considerably in tolerance to complete submergence. The functionality of the responses for underwater gas exchange was evaluated by recording oxygen partial pressures inside the petioles when plants were submerged. • Acclimation to submergence resulted in a decrease in all leaf parameters, including cuticle thickness, in all species irrespective of flooding tolerance. Consequently, internal oxygen partial pressures (pO2) increased significantly in all species until values were close to air saturation. Only in nonacclimated leaves in darkness did intolerant species have a significantly lower pO2 than tolerant species. • These results suggest that submergence-induced leaf plasticity, albeit a prerequisite for underwater survival, does not discriminate tolerant from intolerant species. It is hypothesized that these plastic leaf responses may be induced in all species by several signals present during submergence; for example, low LMA may be a response to low photosynthate concentrations and a thin cuticle may be a response to high relative humidity. [ABSTRACT FROM AUTHOR]

• Nutrient hot spots in the soil have a limited life span, but the costs and benefits for root foraging are still underexposed. We assessed short-term costs that may arise when a nutrient-rich patch induces root proliferation, but then rapidly disappears. • Rumex palustris plants were grown with a homogeneous or a heterogeneous nutrient application. After root proliferation in a nutrient-rich patch, nutrient supply was switched from homogeneous to heterogeneous, and vice versa, or the patch location was changed. • R. palustris proliferated its roots in the rich patch. After switching, the relative growth rates of the roots were adjusted to the novel pattern of nutrient availability. However, the changes in local root biomass lagged behind the rapid shift in nutrient supply, because the root mass realized in specific sectors could not be rapidly relocated. Despite this, R. palustris did not exhibit costs of switching in terms of biomass or nitrogen uptake. • Our data suggest that rapid shifts in uptake rate and redistribution of nitrogen within the plant may have lowered the costs of incorrect root placement. [ABSTRACT FROM AUTHOR]

• Nutrient hot spots in the soil have a limited life span, but the costs and benefits for root foraging are still underexposed. We assessed short-term costs that may arise when a nutrient-rich patch induces root proliferation, but then rapidly disappears. • Rumex palustris plants were grown with a homogeneous or a heterogeneous nutrient application. After root proliferation in a nutrient-rich patch, nutrient supply was switched from homogeneous to heterogeneous, and vice versa, or the patch location was changed. • R. palustris proliferated its roots in the rich patch. After switching, the relative growth rates of the roots were adjusted to the novel pattern of nutrient availability. However, the changes in local root biomass lagged behind the rapid shift in nutrient supply, because the root mass realized in specific sectors could not be rapidly relocated. Despite this, R. palustris did not exhibit costs of switching in terms of biomass or nitrogen uptake. • Our data suggest that rapid shifts in uptake rate and redistribution of nitrogen within the plant may have lowered the costs of incorrect root placement. [ABSTRACT FROM AUTHOR]

• Terrestrial plants experience multiple stresses when they are submerged, caused both by oxygen deficiency due to reduced gas diffusion in water, and by shade due to high turbidity of the floodwater. It has been suggested that responses to submergence arede factoresponses to low light intensity.• We investigated the extent to which submergence and shade induce similar acclimation responses by comparing two terrestrialRumexspecies that differ in their responses to flooding.• Our study confirms that there are strong similarities between acclimation responses to shade and submergence. Petiole length, specific leaf area (SLA), chlorophyll parameters and underwater light-compensation points changed at least qualitatively in the same direction. Maximum underwater photosynthesis rate, however, did discriminate between the functionality of the responses, as the acclimation to submergence appeared to be more effective than acclimation to shade at saturating light.• We conclude that acclimation to submergence involves more than an increase in SLA to achieve the significant reduction of diffusion resistance for gas exchange between leaves and the water column.New Phytologist(2005)doi: 10.1111/j.1469-8137.2005.01404.x© New Phytologist(2005) [ABSTRACT FROM AUTHOR]

Resistance to complete submergence was tested in three Rumex species that occur in the Dutch river forelands. The species differ in both habitat and life history characteristics. The annual or biennial R.maritimus and the biennial or short lived perennial R. palustris grow on frequently flooded mud flats of low elevation, while the perennial R. thyrsiflorus can he found on dykes and river dunes that are seIdom flooded. The flooding characteristics of the habitats of the three species were determined. These data were used to design experiments to determine the survival and biomass development of the three species during submergence and and the influence of plant size and light level on these parameters. It was shown in all three species that plants submerged during daytime were much more resistant to flooding than those submerged at night. This is most probably due to the generation of oxygen or carbohydrates by underwater photosynthesis. Mature plants of the three species showed higher survival after submergence than juvenile plants, which might by caused by higher carbohydrate levels in the taproots of mature plants. In addition, the three species clearly differed in survival and biomass development during submergence. Rumex thyrsiflorus, the species least subjected to flooding, is least tolerant to complete submergence. Rumex maritimus, which can avoid the floods In having a short life cycle, is less tolerant to submergence than R. palustris which has to survive the floods as a vegetative plant. It was noted that some plants that survived the flooding period itself, still died in the following period of drained conditions, possibly due to post-anoxic injury. [ABSTRACT FROM AUTHOR]

The chrysomelid beetle Gastrophysa viridula and the rust fungus Uromyces rumicis both occur on leaves of Rumex crispus and P. obtusifolius. We investigated the effect of beetle grazing or rust infection individually and when combined in sequence on the growth of their hosts in the field. SingIy, beetle Or rust reduced leaf area and plant biomass; the effect was greater on R. crispus, and rust caused greater damage than the beetle. Beetle grazing with subsequent rust infection caused damage no greater than that caused by rust alone, although on R. obtusifolius damage was greater than that from beetle grazing alone. Rust infection of R. obltssifolius with subsequent beetle grazing produced damage similar to that from other treatments involving rust infection. In R. crispus this treatment produced the greatest reduction in biomass. The reductions in root and total plant weight from rust infection with subsequent beetle grazing were accurately predicted by a model including the damage produced by beetle and rust alone and the length of time each was present on the plant. This model also predicted accurately the damage to R. obtusifolius from the beetle followed by rust treatment, but over-estimated by up to 40%, the damage to R. crispsis. This can be explained mainly by an inhibition of rust infection by beetle grazing. [ABSTRACT FROM AUTHOR]

The vegetation history of an important conservation area, the Flow Country in northern Scotland, is described using the results of pollen analysis from two closely spaced cores from the Cross Lochs, eastern Sutherland. Buried lake sediments and shallower surface peats yield a Continuous record covering the Devensian Late-glacial and the Holocene. The earliest Late-glacial pollen spectra recovered suggest a transition from open habitat to more stable communities, dominated by *Empetrum heath. This Windermere Intersradial vegetation shows some variability, with a phase of increased growth of juniper and birch, followed by deteriorating climate and less stable soil conditions in the transition to the Stadial, with Huperzia selago and Salix. There are poorly defined Loch Lomond Stadial and Stadial-Holocene transition periods, characterized by Rumex/Oxyria, after which much wanner, Holocene conditions occur, with a succession of birch-juniper and birch-hazel woodland. Birch persists in small amounts locally, hut the presence of other arboreal pollen is thought to be mostly due to long distance pollen transport. From c. 5500 BP, the landscape is largely treeless, apart from a brief phase of local pine forest c. 4500-4000 BP. These changes arc compared with other pollen records for northern Scotland. The trends in the Late-glacial vegetation are broadly similar to those displayed by other sites, although many of the changes appear to be less extreme than for areas to the south and west. The lack of Artemisia during the Loch Lomond Stadial in the east Sutherland and Caithness area is particularly noteworthy. This may imply more extensive snow cover. The early Holocene is similar to the rest of northern Scotland, but invasion of Betula was more rapid and the later growth of this genus and hazel was not so dense. [ABSTRACT FROM AUTHOR]

The flooding resistance of Rumex maritimus L. and Rumex palustris Sm., two species from frequently flooded areas of river forelands, was studied in two large-scale outdoor experiments. Plants were raised in cohorts and in several stages of development subjected to four weeks of submergence in early summer or in midsummer. The role of under-water shoot clongation in raising foliage above the water line was not equally important in both species. In R. maritimus, survival following either early-or midsummer flooding was restricted mainly to plants which emerged from the water surface by clongating their main shoot. R. palustris was better able to survive submergence, especially under early-summer conditions. As a consequence of survival being restricted to plants in the stern clongation stage, flooded plants of R. maritimus all reproduced in the first growing season and seed output correlated positively with stem length immediately after flooding. This was also the case for R. palustris flooded at midsummer. However, for plants of R. palustris which were flooded in early summer and remained below the water line, flowering was delayed or even postponed to the following season. Variation in seed weight was much larger in R. maritimus than in R. palustris and more clearly related to cohort and treatment effects. Differences between both species in flooding resistance did not seem to be primarily caused by different abilities of shoot elongation, but by differences in submergence tolerance in relation to life-history characteristics. [ABSTRACT FROM AUTHOR]

The effect of temperature and exposure to far red light were compared using positively photoblastic seeds of Cucumis and negatively photoblastic seeds of Rumex. Short exposure of Cucumis seeds to 45 °C was without effect but exposure at 0 °C for 1 to 3 h promoted subsequent germination in white light at a constant temperature of 25 °C. In contrast, white light alternating temperatures 25/10 and 25/5 °C fully counteracted the inhibitory effect of light on germination of Cucumis seeds. The temperature pairs 15/35, 20/35, and 25/35 °C were tested with both Rumex (in darkness) and Cucumis (in light). Seeds of both species had their germination strongly promoted by the 15/35 °C pair. The pair 25/35 °C had a promotive effect in Rumex and no effect in Cucumis, while the pair 20/35 °C was very effective for Rumex but much less so for Cucumis. In experiments in which the alternating pair 25/5 °C was combined with far red (followed by darkness and white light), Rumex and Cucumis seeds behaved similarly. With both, when far red was given during the 5 °C period followed by light or darkness at 25 °C germination was promoted (but the inhibitory effect was completely reversed only where far red was followed by white light). When far red was given at 25 °C followed by white light or darkness during the 5 °C period germination was not promoted. Thus, both positively and negatively photoblastic seeds show the same behaviour in relation to light and temperature when exposed to far red. [ABSTRACT FROM AUTHOR]