Maintenance of xylem hydraulic function during winter in the woody bamboo McClure.

Background: Frost is a common environmental stress for temperate plants. Xylem embolism occurs in many overwintering plants due to freeze-thaw cycles, so coping with freeze-thaw-induced embolisms is essential for the survival of temperate plants.

Methods: This study was conducted on McClure, a woody bamboo species that was grown under natural frost conditions to explore its responses to winter embolisms.

Strategies of tree species to adapt to drought from leaf stomatal regulation and stem embolism resistance to root properties.

Considerable evidences highlight the occurrence of increasing widespread tree mortality as a result of global climate change-associated droughts. However, knowledge about the mechanisms underlying divergent strategies of various tree species to adapt to drought has remained remarkably insufficient. Leaf stomatal regulation and embolism resistance of stem xylem serves as two important strategies for tree species to prevent hydraulic failure and carbon starvation, as comprising interconnected physiological mechanisms underlying drought-induced tree mortality.

Xylem structure and hydraulic characteristics of deep roots, shallow roots and branches of walnut under seasonal drought.

Background: Despite the importance of root hydraulics, there is little research on the in situ dynamic responses of embolism formation and embolism repair of roots distributed in different soil depths in response to different water regimes.

Results: The vessel diameter, hydraulic conductivity, and vulnerability to cavitation were in the order of deep root > shallow root > branch. The midday PLC of shallow root was the highest in the dry season, while the midday PLC of deep root slightly higher than that of branch with no significant difference in the two seasons.

Hydraulic traits are coupled with plant anatomical traits under drought-rewatering cycles in Ginkgo biloba L.

Investigating the responses of plant anatomical traits of trees to drought-rewatering cycles helps us to understand their responses to climate change; however, such work has not been adequately reported. In this study, Ginkgo biloba L. saplings were subjected to moderate, severe, extreme and lethal drought conditions by withholding water according to the percentage loss of hydraulic conductivity (PLC) and rewatering on a regular basis.

Poplar aquaporin PIP1;1 promotes Arabidopsis growth and development.

Background: Root hydraulic conductance is primarily determined by the conductance of living tissues to radial water flow. Plasma membrane intrinsic proteins (PIPs) in root cortical cells are important for plants to take up water and are believed to be directly involved in cell growth.

Results: In this study, we found that constitutive overexpression of the poplar root-specific gene PtoPIP1;1 in Arabidopsis accelerated bolting and flowering.

Coordinated variation in stem and leaf functional traits of temperate broadleaf tree species in the isohydric-anisohydric spectrum.

Stomatal regulation serves as an important strategy for plants to adapt to drought. However, the understanding of how complexes of plant-functional traits vary along the continuum from isohydry to anisohydry remains insufficient. In this study, we investigated a proxy of the degree of iso/anisohydry-the water potential at stomatal closure-and a series of functional traits of leaves and branches in 20 temperate broadleaf species planted in an arid limestone habitat in northern China.

Tradeoff between storage capacity and embolism resistance in the xylem of temperate broadleaf tree species.

Xylem traits are critical plant functional traits associated with water transport, mechanical support, and carbohydrate and water storage. Studies on the xylem hydraulic efficiency-safety tradeoff are numerous; however, the storage function of xylem parenchyma is rarely considered. The effects of a substantial number of xylem traits on water transport, embolism resistance, mechanical support, storage capacity and nonstructural carbohydrate (NSC) content were investigated in 19 temperate broadleaf species planted in an arid limestone habitat in northern China.

Frost fatigue and its spring recovery of xylem conduits in ring-porous, diffuse-porous, and coniferous species in situ.

Frost-induced embolism and frost fatigue are two major aspects of frost damage to xylem water transport in trees. In this study, three species of each ring-porous, diffuse-porous, and coniferous trees growing in situ were used to explore their differences in winter embolism and frost fatigue. Changes in predawn water potential, predawn native embolism, maximal specific conductivity (K), and cavitation resistance (P, xylem water potential at 50% loss of conductivity) of current-year branches were measured from autumn to spring.

Interaction of stomatal behaviour and vulnerability to xylem cavitation determines the drought response of three temperate tree species.

How the mortality and growth of tree species vary with the iso-anisohydric continuum and xylem vulnerability is still being debated. We conducted a precipitation reduction experiment to create a mild drought condition in a forest in the Baotianman Mountains, China, a sub-humid region. Three main sub-canopy tree species in this region were examined.

Corticular photosynthesis drives bark water uptake to refill embolized vessels in dehydrated branches of Salix matsudana.

It is well known that xylem embolism can be repaired by bark water uptake and that the sugar required for embolism refilling can be provided by corticular photosynthesis. However, the relationship between corticular photosynthesis and embolism repair by bark water uptake is still poorly understood. In this study, the role of corticular photosynthesis in embolism repair was assessed using Salix matsudana branch segments dehydrated to -1.

Prediction of temperate broadleaf tree species mortality in arid limestone habitats with stomatal safety margins.

A growing body of evidence highlights the occurrence of increased widespread tree mortality during climate change-associated severe droughts; however, in situ long-term drought experiments with multispecies communities for the prediction of tree mortality and exploration of related mechanisms are rather limited in natural environments. We conducted a 7-year afforestation trial with 20 drought-resistant broadleaf tree species in an arid limestone habitat in northern China, where the species displayed a broad range of survival rates. The stomatal and xylem hydraulic traits of all the species were measured.

Relative contributions of hydraulic dysfunction and carbohydrate depletion during tree mortality caused by drought.

Drought-induced tree mortality has been observed worldwide. Nevertheless, the physiological mechanisms underlying this phenomenon are still being debated. Potted and saplings were subjected to drought and their hydraulic failure and carbon starvation responses were studied.

Genome-Wide Constitutively Expressed Gene Analysis and New Reference Gene Selection Based on Transcriptome Data: A Case Study from Poplar/Canker Disease Interaction.

A number of transcriptome datasets for differential expression (DE) genes have been widely used for understanding organismal biology, but these datasets also contain untapped information that can be used to develop more precise analytical tools. With the use of transcriptome data generated from poplar/canker disease interaction system, we describe a methodology to identify candidate reference genes from high-throughput sequencing data. This methodology will improve the accuracy of RT-qPCR and will lead to better standards for the normalization of expression data.

Phenology-dependent variation in the non-structural carbohydrates of broadleaf evergreen species plays an important role in determining tolerance to defoliation (or herbivory).

Two broadleaf evergreen canopy species (Schima superba and Engelhardia roxburghiana) with different phenologies in a subtropical region of southern China were used to determine the influence of leaf phenology on the impact of an insect pest attack. S. superba regenerates its leaves in February, while E.

Daytime and nighttime wind differentially affects hydraulic properties and thigmomorphogenic response of poplar saplings.

This study tested how wind in daytime and nighttime affects hydraulic properties and thigmomorphogenic response of poplar saplings. It shows that wind in daytime interrupted water balance of poplar plants by aggravating cavitation in the stem xylem under high xylem tension in the daytime, reducing water potential in midday and hence reducing gas exchange, including stomatal conductance and CO2 assimilation. The wind blowing in daytime significantly reduced plant growth, including height, diameter, leaf size, leaf area, root and whole biomass, whereas wind blowing in nighttime only caused a reduction in radial and height growth at the early stage compared with the control but decreased height:diameter ratios.

Leaf economics of evergreen and deciduous tree species along an elevational gradient in a subtropical mountain.

The ecophysiological mechanisms underlying the pattern of bimodal elevational distribution of evergreen tree species remain incompletely understood. Here we used leaf economics spectrum (LES) theory to explain such patterns. We measured leaf economic traits and constructed an LES for the co-existing 19 evergreen and 15 deciduous species growing in evergreen broad-leaved forest at low elevation, beech-mixed forest at middle elevation and hemlock-mixed forest at high elevation in Mao'er Mountain, Guangxi, Southern China (25°50'N, 110°49'E).

Phylogenetic analysis and molecular evolution patterns in the MIR482-MIR1448 polycistron of Populus L.

The microRNAs (miRNAs) miR482 and miR1448 are disease resistance-related miRNAs; the former is ubiquitously distributed in seed plants whereas the latter has only been reported in Populus trichocarpa. The precursor and mature sequences of poplar miR1448 are highly homologous to those of poplar miR482, and these two miRNAs are located in one transcript as a polycistron. Therefore, we hypothesized that the MIR1448 gene may have evolved from the MIR482 gene in poplar.

Variation in embolism occurrence and repair along the stem in drought-stressed and re-watered seedlings of a poplar clone.

Root pressure and plasma membrane intrinsic protein (PIP) availability in the xylem have been recognized to participate in the refilling of embolized conduits, yet integration of the two mechanisms has not been reported in the same plant. In this study, 4-month-old seedlings of a hybrid poplar (Populus alba × Populus glandulosa) clone 84K were subjected to two contrasting soil-water treatments, with the drought treatment involving withholding of water for 17 days to reduce the soil-water content to 10% of the saturated field capacity, followed by a re-watering cycle. The percentage loss of stem hydraulic conductance (PLC) sharply increased, and stomatal conductance and photosynthesis declined in response to drought stress; these processes were gradually restored following the subsequent re-watering.

Variation in soil water uptake and its effect on plant water status in Juglans regia L. during dry and wet seasons.

Temporal and spatial variations in the water status of walnut trees (Juglans regia L.) and the soil in which they were growing were traced by analyzing the differences in hydrogen isotopes during spring and summer in a 7-year-old walnut stand. Walnut root dynamics were measured in both dry and wet seasons.

Osmotic effects of NaCl on cell hydraulic conductivity of corn roots.

In this study, whether the effect of salt (NaCl) stress on cell hydraulic conductivity (L(p)) is via osmotic pressure or ion toxicity and whether abscisic acid (ABA) can release the salt adverse effect were tested. Immediate effects of NaCl and ABA on root cortical cell L(p) of maize (Zea mays L.) were detected by measuring changes in half time of water exchange (T(1/2)) and turgor of individual single cells with a cell pressure probe for at least 1 h.

[Application of pressure probe techniques in studies of plant water relations].

This review introduces the pressure probe technique that was originally designed to detect the turgor of a giant algal cell, then adapted to measure the turgor and other water-relations parameters of higher plants, and now has developed into a diverse tool on researches of plant physiology and eco-physiology. This technique can be used to measure in situ the permeability of cell membranes to water and solutes at the resolution of single cells, and hence is a useful tool to study function and regulation of water channels (aquaporins) of intact plant cells. The recently developed xylem-pressure probe technique is the only way to directly measure the negative pressure in xylem conduits.

Signals controlling root suckering and adventitious shoot formation in aspen (Populus tremuloides).

We determined the effects of removal of leaves, stem axillary buds, or the entire shoot on root suckering (adventitious shoot formation by roots) and basal stem sprouts in 3- and 4-year-old potted seedlings of aspen (Populus tremuloides Michx.). The greatest number of root suckers (67.

Gating of water channels (aquaporins) in cortical cells of young corn roots by mechanical stimuli (pressure pulses): effects of ABA and of HgCl2.

Hydraulic properties (half-time of water exchange, T1/2, and hydraulic conductivity, Lp; T1/2 approximately 1/Lp) of individual cells in the cortex of young corn roots were measured using a cell pressure probe for up to 6 h to avoid variations between cells. When pulses of turgor pressure of different size were imposed, T1/2 (Lp) responded differently depending on the size. Pulses of smaller than 0.