Plant Moisture Status Research Articles

Application of compositional data analysis to determine the effects of heating mode, moisture status and plant species on pyrolysates

Pyrolysate gas mixtures are multivariate and relative in nature. Statistical techniques applied to these data generally ignore their relative nature. Published data for permanent gases (CO, CO2, H2, CH4) and tars produced by pyrolysing 15 wildland fuels were reanalysed using compositional data analysis techniques. Mass and mole fractions were compositionally equivalent. Plant species, moisture status and heating mode effects on compositional balances formed from subsets of pyrolysates were tested. Plant species affected the amount of phenol, primary and secondary/tertiary tars relative to permanent gases and relative amounts of single- and multi-ring compounds. Plant moisture status affected the amount of CO relative to other permanent gases, of H2 to CH4 and tars to phenol. Heating mode and rate strongly influenced pyrolysate composition. Slow heating produced more primary tars relative to multi-ring tars than fast heating convective and combined radiant and convective heating modes. Slow heating produced relatively more compounds with fewer rings and fast heating produced relatively more multi-ring compounds. Compositional data analysis is a well-developed statistical methodology, providing models and methods equivalent to traditional ones, that accounts for the special constraining features of relative data. Future analysis of the compositional data related to wildland fire using compositional techniques is recommended.

Variations in ethylene sensitivity among mungbean [Vignaradiata (L.) Wilczek] genotypes exposed to drought and waterlogging stresses

Ethylene is an important phytohormone that regulates several aspects of plant development including those crucial for drought tolerance. The main aim of the present work was to investigate variability in ethylene sensitivity of mungbeans to seed germination, waterlogging, and leaf senescence, and the underlying transcriptional regulation of ethylene biosynthetic/responsive genes. Significant variation was observed for silver-nitrate-mediated germination inhibition and flooding stress tolerance among the mungbean genotypes. Genotypes with differential ethylene sensitivity (IC-325817 and IC-325756) revealed variable leaf senescence rates upon exposure to exogenously supplied ethephon. Drought induced significant upregulation of VrACS7 and VrERF genes in the more sensitive genotype, implicating the role of plant moisture status in influencing ethylene biosynthesis/perception. Drought-mediated upregulation of VrACS7 transcripts was accompanied by reduced lateral root formation in the more sensitive genotype (IC-325756), although the same did not follow in the less sensitive genotype (IC-325817), which had reduced ethylene responsiveness. These studies emphasize the variability in ethylene sensitivity of mungbeans and reveal a genotype- dependent transcriptional regulation of ethylene biosynthetic/responsive genes upon drought in this waterlogging-sensitive legume crop.

Wpływ niektórych warunków klimatycznych i glebowych na działanie tribenuronu metylu w zależności od dawki i adiuwanta

The controlled environment experiments were carried out to evaluate the activity of tribenuron methyl applied under different climate and soil conditions depending on herbicide rate and application method. The herbicide was applied at two doses (15 and 7.5 g/ha), single and in the mixture with adjuvant Trend 90 EC. It was applied against plants of Anthemis arvensis L. and Papaver rhoeas L. that differed in plant moisture status (dry and wet plants) and type of soil (black soil and podsolic soil). Plant moisture status at the time of herbicide treatment differentiated activity of tribenuron methyl applied as single dosage against examined weed species, especially P. rhoeas. Greater efficacy was obtained when plants were wet during application time. Joint application of herbicide and adjuvant overcame differences in herbicide efficacy related to plant moisture status. Tribenuron methyl applied against both weed species growing on black soil was highly effective, independently on dose and application method. Weeds growing on podsolic soil were less controlled by herbicide used at single dosage than in the mixture with adjuvant. Differences in dose activity were observed, especially in the case of single application. Doświadczenia w warunkach kontrolowanych wykonano w celu oceny działania tribenuronu metylu stosowanego w różnych warunkach klimatycznych i glebowych w zależności od dawki środka oraz sposobu aplikacji. Herbicyd zastosowano w dwóch dawkach (15 i 7,5 g/ha), oddzielnie oraz łącznie z dodatkiem adiuwanta Trend 90 EC. Aplikowano go na rośliny Anthemis arvensis L. i Papaver rhoeas L. charakteryzujące się różnym stopniem uwilgotnienia (rośliny suche i wilgotne) oraz glebowych (czarna ziemia, gleba płowa). Stan uwilgotnienia roślin w momencie wykonywania zabiegu zróżnicował działanie tribenuronu metylu stosowanego samodzielnie w stosunku do badanych gatunków chwastów, a zwłaszcza P. rhoeas. Wyższą skuteczność osiągnięto, gdy w momencie wykonywania zabiegu rośliny były wilgotne. Łączna aplikacja herbicydu z adiuwantem zniwelowała różnice w jego skuteczności w zależności od stanu uwilgotnienia roślin. Tribenuron metylu zastosowany na oba gatunki rosnące na czarnej ziemi wykazał wysoką skuteczność, niezależnie od wysokości dawki oraz sposobu aplikacji. Herbicyd stosowany samodzielnie na glebie płowej niszczył chwasty słabiej niż zastosowany z adiuwantem. Wykazano różnice w działaniu badanych dawek środka, zwłaszcza w przypadku samodzielnej aplikacji.

The Relationship Between Soil Water Potential, Environmental Factors, and Plant Moisture Status for Poblano Pepper Grown Using Tensiometer-Scheduled Irrigation

Managing irrigation using soil moisture sensors for automation can allow for a reduction in water use while avoiding drought stress and maintaining optimum yields in high-value crops. Measurements of plant water status such as leaf water potential and relative water content are often utilized to demonstrate the presence or lack of drought stress in plants subjected to varying soil moisture regimes. Poblano peppers (Capsicum annuum L.) were grown under four automated, tensiometer-controlled irrigation regimes with set points of on/off −30/−25, −40/−35, −50/−45, and −60/−55 kPa and a manually operated treatment with set points of −50/−10 kPa. Soil moisture data were collected at depths of 15 and 25 cm and plant midday leaf water potential and relative water content data were collected throughout the growing season. Yield and fruit quality were unaffected by irrigation treatment. Soil water potential was poorly correlated with plant leaf water potential and relative water content. Plant leaf water potential and relative water content were well correlated with the following environmental factors: air temperature, relative humidity, dew point temperature, and solar radiation. These data indicate that in a non-drought-stressed production system leaf water potential and relative water content may be poor indicators of soil water status because they may be affected by environmental variables to a greater extent than by soil moisture.

Optical sensing estimation of leaf nitrogen concentration in maize across a range of water-stress levels

Optical sensing techniques offer an instant estimation of leaf nitrogen (N) concentration during the crop growing season. Differences in plant-moisture status, however, can obscure the detection of differences in N levels. This study presents a vegetation index that robustly measures differences in foliar N levels across a range of plant moisture levels. A controlled glasshouse study with maize (Zea mays L.) subjected to both water and N regimes was conducted in Ottawa, Canada. The purpose of the study was to identify spectral waveband(s), or indices derived from different wavebands, such as the normalised difference vegetation index (NDVI), that are capable of detecting variations in leaf N concentration in response to different water and N stresses. The experimental design includes three N rates and three water regimes in a factorial arrangement. Leaf chlorophyll content and spectral reflectance (400–1075 nm) were measured on the uppermost fully expanded leaves at the V6, V9 and V12 growth stages (6th, 9th and 12th leaves fully expanded). N concentrations of the same leaves were determined using destructive sampling. A quantitative relationship between leaf N concentration and the normalised chlorophyll index (normalised to well fertilised and well irrigated plants) was established. Leaf N concentration was also a linear function (R2 = 0.9, P < 0.01) of reflectance index (NDVI550, 760) at the V9 and V12 growth stages. Chlorophyll index increased with N nutrition, but decreased with water stress. Leaf reflectance at wavebands of 550 ± 5 nm and 760 ± 5 nm were able to separate water- and N-stressed plants from normal growing plants with sufficient water and N supply. Our results suggest that NDVI550, 760 and normalised chlorophyll index hold promise for the assessment of leaf N concentration at the leaf level of both normal and water-stressed maize plants.

Physiological and field growth responses of oak seedlings to warm storage

The effect of warm storage (15°C) for 0, 15 or 31 days, applied after cold storage until April, and date of lifting to cold storage on the physiological condition and field performance of two-year-old oak seedlings (Quercus robur L.) was investigated. Assessments before planting included plant moisture status, root and shoot dry weight, root growth potential (RGP), while after planting root growth, shoot growth phenology, shoot and root dry matter accumulation and stem quality were assessed. Warm storage effects were large, but lift date effects were small. Warm storage for 31 days reduced height and diameter growth, stem quality, total biomass, root growth, and reduced stem quality in the field, but 15 days storage had a smaller effect. Warm storage delayed bud break and shoot growth cessation but survival was unaffected. The depletion of food reserves during storage and low moisture availability might have caused shoot dieback leading to the development of poor quality stems. There was evidence that dry weight fraction of both the shoot tip and the taproot provided good information on the quality of the stock before planting. RGP was also a good indicator of quality. Electrolyte leakage readings from fine and taproots were not reliable indicators of plant quality.

Scale-dependent mechanisms in the population dynamics of an insect herbivore

A multiscale approach has lead to significant advances in the understanding of species population dynamics. The scale-dependent nature of population processes has been particularly clearly illustrated for insect herbivores. However, one of the most well-studied insect herbivores, the galling sawfly Euura lasiolepis, has to date been examined almost exclusively at fine spatial scales. The preference-performance, plant vigour and larval survival hypotheses are well supported by this species. Here, we test these hypotheses at a spatial scale larger than that previously considered, i.e. across a landscape in northern Arizona represented by an altitudinal gradient encompassing a series of drainages. We also develop a qualitative model for understanding the population dynamics of E. lasiolepis based on patterns of survival and mortality found in this study and previous ones. Gall density was highly variable across the altitudinal gradient, not explained by host plant variables, and thus a poor surrogate for population abundance. These findings for the first time fail to support the plant vigour and preference hierarchy hypotheses for E. lasiolepis. Dispersal limitation most likely explains the lack of support for these hypotheses at this scale. By contrast, sawfly survival, gall abortion, parasitism and larval mortality were well explained by host plant quality variables and altitude. The larval survival hypothesis was well supported and is thus comparatively scale-invariant. A qualitative model developed here highlighted the importance of both willow water status and disturbance in determining host plant quality, as well as an apparent trade off between shoot length and plant moisture status in determining vital rates across the altitudinal gradient. This study thus demonstrated for the first time the scale-dependent nature of mechanisms underlying the population dynamics E. lasiolepis, and identified the interaction between parasitism and altitude as a novel mechanism underlying spatial patterns in the survival and mortality patterns of this species.

Light, soil, and seedling characteristics associated with varying levels of competition in a red pine plantation

Red pine (Pinus resinosa Ait.) seedlings growing under differing levels of competition were evaluated during the fifth growing season following planting, and placed into low, moderate, or high tree classes, as a function of levels of competing vegetation. Tree growth, moisture status, and nutrition were monitored over the growing season. Additionally, site characteristics such as soil temperature and moisture, inorganic nitrogen concentration, mineralized soil nitrogen, and light were measured. Red pine seedlings growing under low competition had an absolute volume growth increase of 795% over the seedlings growing under the heaviest competition. The associated relative volume growth increase during the fifth growing season was 44%. Discriminant analysis was used to describe three classes of trees representing low, moderate, and high levels of competition. Trees growing under low competition had longer and heavier needles, but generally lower nutrient concentrations. Pre-dawn plant moisture status did not vary among competition levels. Soil variables indicated that, in general, the trees growing under low competition occupied warmer, drier, and less fertile microsites, as inorganic soil N and mean monthly mineralized NO3-N and NH4>-N tended to be lower on these microsites. The suite of independent variables was effective in classifying the model data into three tree competition classes, with percent correct classifications of 92, 75, and 100 for low (tree class one), moderate (tree class two), and heavy (tree class three) competition, respectively.

Effect of plant moisture stress and application surface on uptake and translocation of triclopyr with organosilicone surfactant in red maple seedlings

This study investigated the effect of plant moisture stress and surface of application on the absorption, translocation, and "rainfastness" (short-term ability to retain herbicide) of organosilicone-adjuvated (adjuvant added) [14C]triclopyr amine on greenhouse-grown, 4-month-old red maple (Acerrubrum L.) seedlings. Xylem water potentials were −1.6 and −0.9 MPa and leaf conductances were 0.07 and 0.13 cm s−1 for the stressed and control seedlings, respectively. At 2 h, rainfastness was 13% less for stressed seedlings. Uptake increased with time, and by 72 h no effect of moisture stress treatment was apparent. Abaxial absorption into living leaf tissue was 57% greater at 72 h than was adaxial absorption, but application surface did not significantly affect translocation. Plant moisture stress did, however, reduce translocation of herbicide into the shoots and roots. Organosilicone surfactants may enhance long-term triclopyr uptake in water-stressed seedlings, but do not appear to facilitate translocation in stressed seedlings. Plant moisture status, therefore, should continue to be a concern when scheduling herbicide applications.

Effect of plant moisture stress on absorption and translocation of triclopyr in oak seedlings

Ways to maximize herbicide efficacy are of great concern to most forest managers. Many factors influence the efficacy of herbicides, including the physiological status of the plant and its effect on the translocation of herbicides. This study investigated how plant moisture status affected herbicide absorption and translocation. The ester formulation of [14C]triclopyr was applied to the foliage of 8-month-old, container-grown water oak (Quercusnigra L.) and southern red oak (Quercusfalcata Michx.) seedlings. At the time of treatment, seedlings were in soil with average moisture contents of 5 and 35% by weight. Corresponding seedling xylem water potentials averaged −1.8 and −0.3 MPa, respectively. Triclopyr absorption was not significantly affected by the soil moisture treatment. However, translocation to stems and roots was 62 and 48% lower, respectively, in water-stressed seedlings. Water oak absorbed 23% less than southern red oak when averaged over the soil moisture treatments. Scheduling herbicide applications when moisture is plentiful could improve triclopyr efficacy.

PHOTOSYNTHETIC CHARACTERISTICS AND POTENTIAL MOISTURE STRESS FOR THE ACTINORHIZAL SHRUB, MYRICA CERIFERA (MYRICACEAE), ON A VIRGINIA BARRIER ISLAND

Seasonal variations in photosynthesis and water relations parameters were quantified for Myrica cerifera, the dominant woody species on the barrier islands along the eastern shore of Virginia. From June through September of 1989, maximum values were 35 μmol m−‐2 sec−‐1 for net CO2 assimilation, 10.5 mm sec−‐1 for stomatal conductance to water vapor diffusion, and –0.3 MPa for xylem pressure potential at the field site on Hog Island. Midday minimum xylem pressure potential often was less than –1.5 MPa. Data from the field and measurements on glasshouse plants indicated that stomatal opening and photosynthesis were sensitive to leaf water potential (<–0.8 MPa) and the leaf‐to‐air humidity deficit (>1.5 kPa). Using meteorological data and derived photosynthetic responses, predictions indicated that M. cerifera photosynthesis would have been limited at the field site due to nonoptimal air temperatures and humidity deficits on at least 90% of the days during the relatively wet summer of 1989. By comparison, these parameters were expected to limit photosynthesis on all but 2 d, or more than 98% of the time during the relatively dry summer of 1990. The sensitivity of Myrica cerifera to atmospheric humidity and plant moisture status may explain the distributional preference for the more mesic swale sites of barrier islands.

Photosythetic Characteristics and Potential Moisture Strees for the Actinorhizal Shrub, Myrica cerifera (Myricaceae), on a Virginia Barrier Island

Seasonal variations in photosynthesis and water relations parameters were quantified for Myrica cerifera, the dominant woody species on the barrier islands along the eastern shore of Virginia. From June through September of 1989, maximum values were 35 μmol m−-2 sec−-1 for net CO2 assimilation, 10.5 mm sec−-1 for stomatal conductance to water vapor diffusion, and –0.3 MPa for xylem pressure potential at the field site on Hog Island. Midday minimum xylem pressure potential often was less than –1.5 MPa. Data from the field and measurements on glasshouse plants indicated that stomatal opening and photosynthesis were sensitive to leaf water potential (<–0.8 MPa) and the leaf-to-air humidity deficit (>1.5 kPa). Using meteorological data and derived photosynthetic responses, predictions indicated that M. cerifera photosynthesis would have been limited at the field site due to nonoptimal air temperatures and humidity deficits on at least 90% of the days during the relatively wet summer of 1989. By comparison, these parameters were expected to limit photosynthesis on all but 2 d, or more than 98% of the time during the relatively dry summer of 1990. The sensitivity of Myrica cerifera to atmospheric humidity and plant moisture status may explain the distributional preference for the more mesic swale sites of barrier islands.

Suppression of Growth and Plant Moisture Stress of Forsythia with Flurprimidol and XE-1019

Abstract Flurprimidol and XE-1019, applied at 15.0 and 2.5 mg/plant respectively, suppressed shoot dry weight and increased xylem pressure potential of Forsythia spectabilis Spaeth when drought was induced but did not affect leaf size or root dry weight. XE-1019 did not suppress growth when applied on 28 Aug. 1985. Plants treated with flurprimidol in late August had less shoot growth and higher xylem pressure potential than untreated controls or plants treated with XE-1019. Mefluidide applied as a foliar spray at 5000 mg·liter-1 on 25 June 1985 did not suppress growth or affect plant moisture status of forsythia. None of the growth regulators reduced the transpiration rate of forsythia plants. Chemical names used: N-[2,4-dimethyl-5-[[(trifluoromethyl) sulfonyl]amino]phenyl]acetamide (mefluidide); α-(1-methylethyl)- α-[4-trifluoromethoxy)phenyl]-5-pyrimidinemethanol (flurprimidol); (E)-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-ol (XE-1019).

Inclusion of plant moisture status in combination-method estimates of pasture evaporation

An earlier paper considered a combination-type formula for estimation of evaporation under conditions of restricted water supply. The formula involves an “internal conductance” factor. This paper describes relationships of the conductance to indices of moisture status of pasture species, determined over a range of soil-moisture conditions. Once established, these relationships were employed to estimate conductances, which were then used to determine evaporation, over later periods of pasture growth. The investigations demonstrated that inclusion of plant-moisture stress data into a combination formula can afford estimates of pasture evaporation which are significantly better than those obtained by more empirical means.

The Use of a 2-Layer Model to Estimate Soil Moisture Conditions in Kentucky

The verification of a simple two-layer soil moisture model using weekly rainfall and temperature is described. An index related to plant-moisture status is computed from the various parameters in the model. Actual reports of field moisture conditions were collected during an entire growing season in Kentucky; these agreed very well with the computed index. Climatological data, for a period of 20 years at Mayfield, Ky., were used to calculate average weekly values of the index at that location. The annual cycle of the index indicates the average time of onset of wet, dry, and favorable soil moisture conditions.

Plant moisture status effects in estimation of evaporation by a combination method

Various attempts have been made in the past to generalize combination-type evaporation formulae for use under conditions of restricted water supply. A further approach involving measurements of plant moisture status is described. The formula employed includes a crop “internal conductance” factor. First, relationships of this factor to the relative water content, tissue water potential and water vapour diffusion resistance of leaves were investigated for four potato crops. The regression relationships with least scatter, namely those with the relative water content of upper leaves, were employed to estimate internal conductances of three further potato crops under a range of atmospheric and soil moisture conditions. The estimates of evaporation based on these values of conductance were significantly closer to measured values than estimates based on simple empirical relationships involving, for example, the ratio of actual to potential evaporation.

Effect of Water Regime on the Sucrose-Enzyme Relationships of Sugarcane Desiccated with Paraquat

Immature sugarcane was given variable-water regimes in sand culture and subsequently treated with a powerful desiccant, the bipyridylium herbicide Paraquat, applied as a 0.05-percent aqueous foliar spray. There were two objectives: (a) To evaluate the effects of water regime on sucroseenzyme relationships in desiccating sugarcane; and (b) to determine whether controlled water regimes could effectively modify Paraquat activity in sugarcane. Tissue samples were harvested for moisture, sugar and enzyme analyses at 1,3 and 9 days after Paraquat application. Low water supply (1 liter per day) reduced total fresh weights and stalk weights, and increased sucrose content of immature storage tissue. Paraquat significantly lowered total fresh weights, stalk weights, sheath moisture and leaf sucrose by the 9-day harvest. Desiccant action was generally more rapid within the low-water regime. High- and intermediate-water regimes tended to modify Paraquat activity at 1 or 3 days, but its ultimate effects were comparable regardless of water regime. No evidence was found to support the theory that desiccating cane accumulates water as a function of continued water absorption when transpiration has ceased. Acid invertase was suppressed by Paraquat, an effect consistent with earlier findings. The suppression was most severe in the low-water regime. Low-water supply significantly lowered invertase level but the response was not consistent at all harvests. Acid phosphatase and ATP-ase were severely repressed by Paraquat in leaves but not in immature storage tissue. An explanation was offered in terms of distinct chloroplast and mitochondrial enzymes rather than localized Paraquat action. For both enzymes the desiccant repression was significantly more severe in the high-water regime at 1 or 3 days, but water regime showed no effect at 9 days. Paraquat significantly increased ß-amylase in leaves (consistent with earlier studies), particularly within the high-water regime. In immature stem tissue ß-amylase was repressed by high water in Paraquat-free plants. Paraquat eliminated the water effect. Peroxidase was increased in storage tissue by Paraquat. This response was statistically significant only under conditions of low-water supply. It is concluded that variable water regimes can modify the rate of initial Paraquat activity in sugarcane; however, the ultimate effects of Paraquat will not be changed under conditions of thorough chemical application. Under field conditions of marginal chemical penetration, the plant's moisture status might play a more decisive role in determining the desiccant's effectiveness.

Soil and Plant Moisture Relations of Red Pine Growing on a Shallow Soil

AbstractThe relationship of plant moisture status to soil moisture content was studied in a 25‐year‐old red pine, Pinus resinosa Ait., plantation on 60 cm of channery silt loam soil over fractured siltstone bedrock. Two of the four‐tree plots received summer rainfall; rainfall was excluded from the remaining two plots by a plastic ground covering. The relative turgidity and needle moisture content of current‐ and second‐year needles were measured; only the second‐year needle relative turgidity was significantly correlated with soil moisture content. Wood moisture content was not correlated with soil moisture content. The dry weight of current‐year needles was closely related to the soil moisture availability during the period of growth. The degree to which the underlying bedrock was fractured, allowing roots to penetrate, was a primary factor in survival.