Sap Exudation Research Articles

An Outbreak of Gummosis of Mango Trees Caused by Lasiodiplodia theobromae in Guangxi, South China.

Mango (Mangifera indica L.) is an economically important fruit in southern provinces of China. In May 2012, field surveys including 2,250 mango trees were done in nine orchards of five different counties in Guangxi Province. An outbreak of gummosis was observed in the province involving over 30,000 ha with an average of 50% disease incidence (DI) and a maximum of 70% in some orchards. Until then, gummosis had been considered a common but not serious disease. In 2012, high temperatures in April and extensive rain in May favored increased disease development. Infected plants showed abundant gum secretion from branches, stems, and main trunks. Some branches died from the disease. During the early stages of infection, branches or stems turned brown followed by xylem necrosis and exudation of a milky sap. The sap turned yellow and finally formed amber gum within several days. Initially, the gum appeared as small droplets, increasing in number, and covering most of the branches and the trunk with bark cracking under severe conditions. On potato dextrose agar (PDA), isolates with similar morphology were consistently recovered from symptomatic plant tissues after surface sterilization in 75% ethanol for 30 seconds and then in 0.1% mercuric chloride for 1 min. Five single-spore isolates from five different locations in Guangxi Province were used to evaluate characteristics of the pathogen. On PDA, cultures were gray with an irregularly distributed, fast-growing, and fluffy aerial mycelium, showing a dark underside as the colony changed from greenish to black after 5 days at 28°C. After 1 month, cultures produced globose pycnidia. Conidia were elliptical and hyaline when immature, becoming dark brown and one-septate, longitudinally striate when mature, and ranged from 20.0 to 28.0 × 10.5 to 16.0 μm (average 23.3 × 13.7 μm). Paraphyses produced within the tissues of pycnidia were hyaline, cylindrical, nonseptate, and up to 61 μm long. The fungus was identified as Lasiodiplodia theobromae (Pat.) Griffon & Maubl. (=Botryosphaeria rhodina (Cooke) Arx) based on morphological and cultural characteristics (1,2). The rDNA internal transcribed spacer region of one isolate showed 100% identity to L. theobromae (GenBank HM346876.2) and was deposited in GenBank (JX982240). Pathogenicity of the five isolates was tested in the field on healthy tissues in June 2012. Five green twigs and five 3-year-old branches were used. Three wounds were made on each twig or branch with a sterilized needle. Mycelial plugs were placed on wounds and covered with Parafilm. Uncolonized PDA plugs were used as controls. Two weeks later, typical brown lesions were observed on inoculated branches, and gum exuded from infected wounds. No symptoms were seen on the controls. Koch's postulates were fulfilled by reisolation of L. theobromae from diseased branches. L. theobromae is well documented as a pathogen of mango. In China, the disease was observed in the 1990s in Hainan Province, and the causal agents were identified as L. theobromae and Colletotrichum gloeosporioides Penz. & Sacc based on morphological observation (3). To our knowledge, this is the most severe outbreak reported from China.

Increased Expression of a Phloem Membrane Protein Encoded by NHL26 Alters Phloem Export and Sugar Partitioning in Arabidopsis

The complex process of phloem sugar transport involves symplasmic and apoplasmic events. We characterized Arabidopsis thaliana lines ectopically expressing a phloem-specific gene encoding NDR1/HIN1-like26 (NHL26), a putative membrane protein. NHL26 overexpressor plants grew more slowly than wild-type plants, accumulated high levels of carbohydrates in mature leaves, and had a higher shoot biomass, contrasting with slower root growth and a lower seed yield. Similar effects were observed when NHL26 was overexpressed in companion cells, under the control of a companion cell-specific promoter. The soluble sugar content of the phloem sap and sink organs was lower than that in the wild type, providing evidence of a sugar export defect. This was confirmed in a phloem-export assay with the symplastic tracer carboxyfluorescein diacetate. Leaf sugar accumulation was accompanied by higher organic acid, amino acid, and protein contents, whereas analysis of the metabolite profile of phloem sap exudate revealed no change in amino acid or organic acid content, indicating a specific effect on sugar export. NHL26 was found to be located in the phloem plasmodesmata and the endoplasmic reticulum. These findings reveal that NHL26 accumulation affects either the permeability of plasmodesmata or sugar signaling in companion cells, with a specific effect on sugar export.

Plant phloem sterol content: forms, putative functions, and implications for phloem-feeding insects

All eukaryotes contain sterols, which serve as structural components in cell membranes, and as precursors for important hormones. Plant vegetative tissues are known to contain mixtures of sterols, but very little is known about the sterol composition of phloem. Plants are food for many animals, but plant-feeding arthropods (including phloem-feeding insets) are unique among animals in that they have lost the ability to synthesize sterols, and must therefore acquire these essential nutrients from their food, or via endosymbionts. Our paper starts by providing a very brief overview of variation in plant sterol content, and how different sterols can affect insect herbivores, including those specializing on phloem. We then describe an experiment, where we bulk collected phloem sap exudate from bean and tobacco, and analyzed its sterol content. This approach revealed two significant observations concerning phloem sterols. First, the phloem exudate from each plant was found to contain sterols in three different fractions – free sterols, sterols conjugated to lipids (acylated), and sterols conjugated to carbohydrates (glycosylated). Second, for both plants, cholesterol was identified as the dominant sterol in each phloem exudate fraction; the remaining sterols in each fraction were a mixture of common phytosterols. We discuss our phloem exudate sterol profiles in a plant physiology/biochemistry context, and how it relates to the nutritional physiology/ecology of phloem-feeding insects. We close by proposing important next steps that will advance our knowledge concerning plant phloem sterol biology, and how phloem-sterol content might affect phloem-feeding insects.

가래나무 수액와 고로쇠나무의 출수량에 미치는 영향 인자 분석 : (III) 인제 지역

본 연구에서는 강원도 인제지역의 가래나무의 수액 출수와 영향인자들을 분석하여 고로쇠나무 수액의 대체자원으로서 최적의 수액 출수 조건을 얻고자 출수량, 흉고직경, 시험지의 기온과 상대습도를 2008년 2월 1일~3월 31일의 기간에 측정하여 출수량과 다른 측정값들과의 상관성 분석을 수행하였고 고로쇠나무의 경우와 비교 분석하였다. 가래나무 수액의 출수는 고로쇠나무 경우와 유사한 출수 시기와 출수 기간을 가지고 있었으나 가래나무 수액 출수는 출수 기간의 초기에 집중되었다. 동일 지역의 고로쇠나무 수액의 출수량은 나무의 흉고직경이 증가할수록 증가한 것과 달리 가래나무 수액의 출수량은 흉고직경 증가에 따른 뚜렷한 증감을 관찰할 수 없었다. 수액 출수량이 높은 개체의 경우 고로쇠나무와 가래나무 모두 단위 흉고직경 당 출수량은 높은 것으로 나타났으며, 고로쇠나무의 흉고직경 당 출수량은 전체 평균 <TEX>$0.9{\pm}0.1{\ell}/cm$</TEX>으로 가래나무의 평균 <TEX>$0.3{\pm}0.1{\ell}/cm$</TEX>에 대비하여 3배에 달하였다. 수액이 많이 출수되는 날의 기온와 상대습도는 고로쇠나무와 가래나무 경우 모두 서로 유사하게 나타나 가래나무 수액 출수는 고로쇠나무의 경우와 같이 외부 기후 조건에 많이 영향받는 것으로 판단되었다. 수액출수량과 기온 및 대기 습도와의 상관 분석에서 가래나무의 경우 일중 최저 기온(P < 0.05)이, 고로쇠나무의 경우 기온차(P < 0.01)가 수액 출수량에 가장 유의적으로 영향을 미치는 것으로 나타났다. 이러한 결과를 볼 때 가래나무의 수액 출수는 고로쇠나무와 유사한 기후 조건에서 발생하나 그 수액 출수량은 고로쇠나무보다 적고 이에 영향하는 주요 인자 또한 다른 것으로 생각된다. This study was carried out to investigate the optimum condition for sap exudation of Juglans mandshurica in comparison with Acer mono Max. trees in a site of Inje-Gun, Gangwon-Do, Korea. Amount of sap exudation, air temperature, relative air humidity and tree diameter at breast height (DBH) were monitored for the period of February 1 through March 31, 2008, and correlation analysis of several factors affecting on sap exudation was carried out. Sap exudation from J. mandshurica initiated on Feb. 28 as the same time in case of A. mono and continued for a month, and enhanced in early March compared to around the middle of March for A. mono. The amount of sap of A. mono was linearly proportional to the diameter at breast height (DBH) but there was no apparent relationship for J. mandshurica. As the amount of sap exudation per tree increased then sap exudation per unit DBH was also linearly proportional in both J. mandshurica and A. mono. The amount of sap exudation per unit DBH of J. manshurica were <TEX>$0.3{\pm}0.1{\ell}/cm$</TEX> on average, which was one third times of <TEX>$0.9{\pm}0.1{\ell}/cm$</TEX> for A. mono. During the days of enhanced sap exudation, the atmospheric conditions such as air temperature and relative humidity around J. manshurica trees were very similar with those of A. mono. The minimum temperature was a significant factor affecting the amount of sap of J. mandshurica whereas the range of temperature was the principal factor for A. mono. In conclusion, the sap of J. mandshurica exudated in atmospheric conditions similar to A. mono, but the amount of sap was affected by different atmospheric factors compared to A. mono.

A Mathematical Model of Sap Exudation in Maple Trees Governed by Ice Melting, Gas Dissolution, and Osmosis

We develop a mathematical model for sap exudation in a maple tree that is based on a purely physical mechanism for internal pressure generation in trees in the leafless state. There has been a long-standing controversy in the tree physiology literature over precisely what mechanism drives sap exudation, and we aim to cast light on this issue. Our model is based on the work of Milburn and O'Malley [Can. J. Bot., 62(10):2101-2106, 1984] who hypothesized that elevated sap pressures derive from compressed gas that is trapped within certain wood cells and subsequently released when frozen sap thaws in the spring. We also incorporate the extension of Tyree [in Tree Sap, pp. 37-45, eds. M. Terazawa et al., Hokkaido Univ. Press, 1995] who argued that gas bubbles are prevented from dissolving because of osmotic pressure that derives from differences in sap sugar concentrations and the selective permeability of cell walls. We derive a system of differential-algebraic equations based on conservation principles that is used to test the validity of the Milburn-O'Malley hypothesis and also to determine the extent to which osmosis is required. This work represents the first attempt to derive a detailed mathematical model of sap exudation at the micro-scale.

Interaction of xylem and phloem during exudation and wound occlusion in Cucurbita maxima

Collection of cucurbit exudates from cut petioles has been a powerful tool for gaining knowledge on phloem sap composition without full notion of the complex exudation mechanism. Only few publications explicitly mentioned that exudates were collected from the basal side of the cut, which exudes more copiously than the apical side. This is surprising since only exudation from the apical side is supposedly driven by phloem pressure gradients. Composition of carbohydrates and pH values at both wounding sides are equal, whereas protein concentration is higher at the basal side. Apparently, exudation is far more complex than just the delivery of phloem sap. Xylem involvement is indicated by lower protein concentrations after elimination of root pressure. Moreover, dye was sucked into xylem vessels owing to relaxation of negative pressure after cutting. The lateral water efflux from the vessels increases turgor of surrounding cells including sieve elements. Simultaneously, detached parietal proteins (PP1/PP2) induce occlusion of sieve plates and cover wound surface. If root pressure is strong enough, pure xylem sap can be collected after removal of the occlusion plug at the wound surface. The present findings provide a mechanism of sap exudation in Cucurbita maxima, in which the contribution of xylem water is integrated.

Response pattern of amino compounds in phloem and xylem of trees to soil drought depends on drought intensity and root symbiosis

This study aimed to identify drought-mediated differences in amino nitrogen (N) composition and content of xylem and phloem in trees having different symbiotic N(2)-fixing bacteria. Under controlled water availability, 1-year-old seedlings of Robinia pseudoacacia (nodules with Rhizobium), Hippophae rhamnoides (symbiosis with Frankia) and Buddleja alternifolia (no such root symbiosis) were exposed to control, medium drought and severe drought, corresponding soil water content of 70-75%, 45-50% and 30-35% of field capacity, respectively. Composition and content of amino compounds in xylem sap and phloem exudates were analysed as a measure of N nutrition. Drought strongly reduced biomass accumulation in all species, but amino N content in xylem and phloem remained unaffected only in R. pseudoacacia. In H. rhamnoides and B. alternifolia, amino N in phloem remained constant, but increased in xylem of both species in response to drought. There were differences in composition of amino compounds in xylem and phloem of the three species in response to drought. Proline concentrations in long-distance transport pathways of all three species were very low, below the limit of detection in phloem of H. rhamnoides and in phloem and xylem of B. alternifolia. Apparently, drought-mediated changes in N composition were much more connected with species-specific changes in C:N ratios. Irrespective of soil water content, the two species with root symbioses did not show similar features for the different types of symbiosis, neither in N composition nor in N content. There was no immediate correlation between symbiotic N fixation and drought-mediated changes in amino N in the transport pathways.

Critical factors in the limited occurrence of the Japanese tree sap mite Hericia sanukiensis (Acari: Astigmata: Algophagidae) inhabiting the sap of the oak Quercus acutissima

Hericia sanukiensis (Astigmata: Algophagidae) is a semi-aquatic mite inhabiting fermented sap flux of the Japanese sawtooth oak (Quercus acutissima) and utilizes Nitidulidae (Coleoptera) as the dispersal (phoretic) carrier. Although nitidulid beetles are commonly found in sap flux, the occurrence of H. sanukiensis has been extremely limited to a few trees in Shikoku Island, Kagawa Prefecture, Japan. To elucidate the critical factors limiting the occurrence of this species, we compared several physical and biological characteristics of sap-exudation points, including the structure and temperature of tree trunks, period and abundance of sap exudation, and seasonal occurrence and dispersal behavior of nitidulid beetles between environments with and without mites. During the two consecutive years of field research, we found that only sap-exudation points with obvious tree holes (ringent area >10 cm², depth >10 cm) had sustained mite populations throughout the observation period. In contrast, for the sap-exudation points lacking tree holes, H. sanukiensis temporally (from spring to autumn) colonized only when the sap production was considerably high. Thus, we suggest that the settlement of H. sanukiensis populations requires tree holes as an overwintering habitat. Nitidulid beetles also concentrated in areas with high sap production and did not disperse from such habitats during the sap flow season. This indicates that H. sanukiensis mites may only disperse and colonize new habitats at very limited opportunities, such as drastic habitat deterioration, which may promote the movement of their carrier. Taken together, these findings may explain the limited occurrence of this mite species.

Water status in Mesembryanthemum crystallinum under heavy metal stress

Heavy metals (HMs) are known to have negative effects on plant water status; however, the mechanisms by which plants rearrange their water relations to adapt to such conditions are poorly understood. Using the model plant Mesembryanthemum crystallinum, we studied disturbances in water status and rapid plant defence responses induced by excess copper or zinc. After a day of HM stress, reductions in root sap exudation and water deficits in leaf tissues became evident. We also observed several primary adaptive events, including a rapid decrease in the transpiration rate and progressive declines in the leaf-cell sap osmotic potential. Longer HM treatments resulted in reductions of total and relative water contents as well as proline accumulation, an increase in water retention capacity and changes in aquaporin gene expression. After 3 h of HM exposure, leaf expression of the McTIP2;2 gene, which encodes tonoplast aquaporin, was suppressed more than two-fold, thus representing one of the earliest responses to HM treatment. The expression of three additional aquaporin genes was also reduced starting at 9 h; this effect became more prominent upon longer HM exposure. These results indicate that HMs induce critical rearrangements in the water relations of M. crystallinum plants, based on the rapid suppression of transpiration flow and strong inhibition of root sap exudation. These effects then triggered an adaptive water-conserving strategy involving differential regulation of aquaporin gene expression in leaves and roots, further reductions in transpiration, and an accelerated switch to CAM photosynthesis.

고로쇠나무 수액의 출수에 미치는 영향 인자 분석 : (II) 함양 지역

본 연구는 경상남도 함양군 지리산의 고로쇠나무 수액의 출수와 영향 인자들을 분석하여 최적의 출수 조건을 얻는데 기여하고자, 출수량과 시험지의 기온 및 상대습도, 흉고직경 그리고 수액내 당 함량 사이의 상관성을 분석하였다. 고로쇠나무의 흉고직경에 비례하는 출수량과의 상관성은 출수량이 많은 날에 높았고 출수 일수와 시기는 공시목 사이에 큰 차이점이 없었다. 출수량이 높았던 날들의 기온은 일평균기온 <TEX>$1.2{\pm}1.6^{\circ}C$</TEX>, 일최저기온 <TEX>$-4.3{\pm}1.5^{\circ}C$</TEX> 그리고 일최고기온 <TEX>$11.8{\pm}1.9^{\circ}C$</TEX>로 나타났다. 수액 출수는 기온이 영하의 온도를 지속하거나 영상의 온도를 지속할 경우에는 관찰되지 아니하였다. 기온과 출수량과의 상관 분석에서 일최고기온과 일평균기온이 유의적(p < 0.05)으로 관련성이 있는 것으로 나타났다. 수액의 출수 기간 동안 자당의 농도는 일정 수준을 유지 하였으나 출수가 종료되는 시점에서 급격하게 감소하였다. This study was carried out to investigate the optimum condition for sap exudation of Acer mono Max. tree in a site of Mt. Jiri, Hamyang-gun, Korea. Amount of sap exudation, air temperature, relative air humidity, tree diameter at breast height (DBH) and sugar content in sap were monitored during the early springtime, and correlation analysis of several factors was carried out to explain tree-to-tree and date-to-date variations in sap exudation. The correlation, linearlyassociated between DBH and sap amount, was strengthened as daily amount of sap increased, but there was no significant tree-to-tree variation in time and period for sap exudation. When amount of sap exudation was above 10 liter/day, the mean air-temperature was averaged at <TEX>$1.2{\pm}1.6^{\circ}C$</TEX>, the minimum at <TEX>$-4.3{\pm}1.5^{\circ}C$</TEX> and the maximum at <TEX>$11.8{\pm}1.9^{\circ}C$</TEX>. The maximum air temperature and mean air temperature were significant (p < 0.05) factors for amount of sap in correlation analysis to explain date-to-date variation in sap exudation. Sucrose content in sap was in the range of 1.5 and 1.7% during exudation days, but sharply reduced to 0.6% level at the end of exudation period.

고로쇠나무 수액의 출수에 미치는 영향 인자 분석 : (I) 광양지역

본 연구는 전라남도 광양시 백운산의 고로쇠나무 수액의 출수와 영향인자들을 분석하여 최적의 수액출수 조건을 얻고자 출수량, 고로쇠나무 흉고직경, 시험지의 기온과 상대습도를 2008년 1월 15일~3월 28일의 기간에 측정하여 출수량과 다른 측정값들과의 상관성 분석을 수행하였다. 수액 출수량은 고로쇠나무의 직경이 클수록 증가하였으며 출수에 필요한 최소 흉고직경은 17.1 cm로 분석되었고, 출수 시기는 직경별로 차이가 없었다. 수액 출수가 관찰될 때 일최저기온은 <TEX>$-2.4{\pm}1.5^{\circ}C$</TEX>, 그리고 일최고기온은 <TEX>$6.0{\pm}1.8^{\circ}C$</TEX>로 영상과 영하의 기온이 교차 하였고, 반면에 하루 종일 영상 혹은 영하의 기온을 유지시 출수가 관찰되지 아니하였다. 수액 출수량과 기온 및 대기습도와의 상관분석에서 수액출수량은 일최고기온, 일교차, 일최고습도, 일최저습도, 일평균습도에 유의성이 있었으며, 수액출수량과 일최고기온의 상관계수는 0.768 (P < 0.01)로 가장 높게 나타났다. 줄이들 인자들에 대한 편상관 분석결과 일최고기온이 주요 영향인자이었다. 수액 출수에는 일중 영하와 영상의 기온이 교차해야 하고 일최고기온이 높을수록, 그리고 고로쇠나무의 흉고직경이 클수록 출수량이 높았다. This study was carried out to investigate the optimum condition for sap exudation of Acer mono Max. tree in a site of Mt. Baekun, Kwangyang city, Korea. Amount of sap exudation, air temperature, relative air humidity and tree diameter at breast height (DBH) were monitored for the period of January 5 through March 28, 2008, and correlation analysis of several factors affecting on sap exudation was carried out. As the diameter of Acer mono at breast height increased, the amount of sap was linearly proportional. Sap exudation initiated at February 18, and occurred intensively in the period of February 28 through March 10, resulting in 84% of total sap amount by volume. During sap exudation, the minimum temperature was averaged at <TEX>$-2.4{\pm}1.5^{\circ}C$</TEX> and the maximum at <TEX>$6.0{\pm}1.8^{\circ}C$</TEX>, while there was no sap exudation whenever temperature was below or above <TEX>$0^{\circ}C$</TEX> all the day long. The maximum temperature, range of temperature and the maximum, minimum and mean humidities in air were significant factors affecting on amount of sap. The maximum air temperature had the highest correlation coefficient with 0.768 (P < 0.01) and was also considered as the principal factor by partial-correlation analysis. These results showed that sap exudation required daily air-temperature fluctuation from below to above <TEX>$0^{\circ}C$</TEX>, and the amount of sap was strongly dependent on the highest daily-temperature and DBH of tree.

Transient and permanent changes of xylem sap exudation by root systems of Zea mays after application of hydrostatic and osmotic forces

Effects of relatively small changes of hydrostatic and osmotic pressure on root exudation were studied with maize (Zea mays L.) plants grown in hydroculture to estimate the root reflection coefficient for the applied osmolyte (PEG 600). During the first seconds after a change in hydrostatic pressure, the exudation rate measured with a microflow sensor was instantaneously and strongly changed due to elastic deformation of the metaxylem vessels in the branched part of the main root axis. In osmotic experiments, a time of 10–20 s was required before the maximum change of the exudation rate was recorded. This retardation can be explained by diffusive saturation of the non-agitated root surface film and radial turgor propagation. A new standing osmotic gradient was reached within 4 min after a change of the water potential difference (osmotic, hydrostatic). The steady-state exudation rate J was altered by osmotic and hydrostatic forces with nearly equal efficiencies when branch roots were not injured. Hence, the reflection coefficient of the intact root for PEG 600 was close to unity. The results are in accord with nearly ideal reverse osmosis at high rates of water uptake by roots and confirm the absence of a significant hydraulic bypath circumventing the protoplasts.

K+ deprivation induces xylem water and K+ transport in sunflower: evidence for a co-ordinated control

The effect of K+ deprivation on water and K+ transport in roots was studied in sunflower plants. Deprivation was achieved in two different ways: by removing K+ from the growth medium for varying intervals; and by growing plants permanently in a low-K+ medium. Removal of K+ from the growth medium for a few hours prompted a significant increase in xylem sap exudation, associated with an increase in root hydraulic conductivity; however, it did not give rise to any significant change in plant K+ content, nor did it favour root K+ exudation. By contrast, prolonged K+ deprivation led to a decline in the internal K+ content and stimulated water and K+ transport in roots. Leaf application of K+ (Rb+) in plants grown permanently in a low-K+ medium inhibited the effect of K+ deprivation on root water and K+ transport, without significantly modifying the internal K+ content of the plants. This treatment had no effect on normal-K+ plants. These results suggest the existence of mechanisms enabling perception of plant K+ status and/or K+ availability in the medium, which trigger transduction processes governing the transport of water and K+ from the root to the shoot.

Influence of sampling time and sap extraction methodology on xylem pH values in two grapevine varieties grown under drought conditions

The effect of differences in applied pressure and time of sampling on pH values of xylem sap collected using the leaf pressurization technique was examined in two grapevine varieties originating from contrasting habitats ( Vitis vinifera L., cvs. Sabatiano and Mavrodafni) after subjecting them to drought. Three fractions of xylem sap exudates were collected from each leaf according to differences in applied pressure; fractions (I), (II) and (III) corresponding to 1 MPa, 2 MPa and 2.5 MPa pressure, respectively. The pH values in fraction (I) were significantly lower than those in fractions (II) and (III). The sap pH values in fraction (III) seemed to better correspond to changes in leaf apoplastic pH. The time of sampling was found to strongly influence xylem pH values. In particular, a positive relationship between predawn xylem pH values and soil drying was observed. Conversely, xylem pH values measured later during the day (i.e. at 8:00, 9:00 and 10:00 am) were not significantly affected by the reduction in soil water availability in both varieties. It is suggested that the most suitable period for sap sampling in order to better discriminate drought effects on xylem sap pH is at predawn. Furthermore, there were significant differences in pH values as well as in the sensitivity of stomatal conductance to pH between the two varieties. These differences might be related to strategy differences between grapevine varieties for adaptation to drought.

Life history of the newly discovered Japanese tree sap mite, Hericia sanukiensis (Acari, Astigmata, Algophagidae)

Hericia sanukiensis (Acari, Algophagidae) is a species of tree sap mite which has been newly discovered in the sap flux of oak trees (Quercus acutissima). In this study, we have clarified the life history of H. sanukiensis at the onset of sap exudation in spring, overwintering deutonymphs molt to tritonymphs as their molting is exacerbated by the sugar contained in the tree sap, and develop to adulthood and reproduce. The mite colony develops as long as the sap continues to exude during the spring and summer. In this period, most of the protonymphs develop into tritonymphs directly bypassing the deutonymphal stage completely. Facultative deutonymphs which arise in the summer season are phoretic morphs. They attach to coleopteran insects, especially of the family Nitidulidae, as carriers by which to disperse. In autumn (when sap exudation terminates), most of the protonymphs molt to non-phoretic deutonymphs. In winter (without sap exudation), the mite colony is composed only of non-phoretic deutonymphs.

Quantitative relationships between boron and mannitol concentrations in phloem exudates of Olea europaea leaves under contrasting boron supply conditions

Boron remobilization (BR) occurs in plants that form and export phloem–mobile borate–polyol complexes. Previous studies demonstrate that a quantitative relationship exists between polyol translocation and BR. Here we investigate if mannitol translocation is quantitatively related to BR in olive plants thus allowing acclimation to boron limiting conditions. Plants were cultivated under different boron supply ranging from adequate (23 μM) to insufficient or zero supply (0.5 μM or 0 μM). Measurement of boron in the leaf phloem sap exudates (BP) of olive leaves of low or zero boron supply treatments showed that, whereas boron was remobilized, its absolute amounts in the phloem were lower compared to the control. However, BR from source leaves at 0.5 μM or 0 μM was maintained at relatively high levels in regard to the amounts of boron available in the cells of these leaves, indicating a strategy of the source leaves to remobilize boron by depleting their cell sap boron pool. Concurrently, in the above treatments, leaf phloem mannitol (MP) was up to two-fold higher, resulting in a up to five-fold higher ratio of mannitol to boron in the phloem (MP/BP), compared to the control. Furthermore, both MP and MP/BP were negatively correlated with cell sap boron concentration of the leaves indicating the trend for BR under boron limitation. It is concluded that, in this plant species, mannitol concentrations in the leaf phloem may be involved in the promotion of BR under inadequate external supply of boron.

Toward an improved model of maple sap exudation: the location and role of osmotic barriers in sugar maple, butternut and white birch

Two theories have been proposed to explain how high positive pressures are developed in sugar maple stems when temperatures fluctuate around freezing. The Milburn-O'Malley theory proposes that pressure development is purely physical and does not require living cells or sucrose. The osmotic theory invokes the involvement of living cells and sucrose to generate an osmotic pressure difference between fibers and vessels, which are assumed to be separated by an osmotic barrier. We analyzed wood of Acer saccharum Marsh., Juglans cinerea L. and Betula papyrifera Marsh. (all generate positive pressures) examining three critical components of the osmotic model: pits in cell walls, selectivity of the osmotic barrier and stability of air bubbles under positive xylem pressure. We examined the distribution and type of pits directly by light and scanning electron microscopy (SEM), and indirectly by perfusion of branch segments with fluorescent dyes with molecular masses similar to sucrose. The latter approach allowed us to use osmotic surrogates for sucrose that could be tracked by epifluorescence. Infusion experiments were used to assess the compartmentalization of sucrose and to determine the behavior of gas bubbles as predicted by Fick's and Henry's laws. The SEM images of sugar maple revealed a lack of pitting between fibers and vessels but connections between fiber-tracheids and vessels were present. Fluorescein-perfusion experiments demonstrated that large molecules do not diffuse into libriform fibers but are confined within the domain of vessels, parenchyma and fiber-tracheids. Results of the infusion experiments were in agreement with those of the fluorescein perfusions and further indicated the necessity of a compartmentalized osmolyte to drive stem pressure, as well as the inability of air bubbles to maintain such pressure because of instability. These results support the osmotic model and demonstrate that the secondary cell wall is an effective osmotic barrier for molecules larger than 300 g mol(-1).

Effects of Silicon on Photosynthesis of Young Cucumber Seedlings Under Osmotic Stress

ABSTRACT Effects of silicon (Si) application on photosynthesis of solution-cultured cucumber seedlings were investigated under osmotic stress and unstressed conditions. In unstressed conditions, silicon application had no effect on growth and photosynthetic parameters. The responses of the photosynthetic parameters to abruptly imposed osmotic stress did not differ between silicon treatments. After 1 week exposure to osmotic stress, growth reduction was observed, but it was less severe in seedlings grown with silicon than in those without silicon. Although there were no differences between silicon treatments in stomatal conductance, transpiration rate, cuticular transpiration, or xylem sap exudation rate under osmotic stress, leaf intercellular carbon dioxide (CO2) concentration was significantly lower and photosynthetic rate tended to be higher in seedlings supplied with silicon. These results suggested that the silicon-induced alleviation of growth reduction under osmotic stress in cucumber was due to amelioration of stress-induced damage of leaf tissues rather than to improvement of leaf water status.

Variation in Eastern Cottonwood (&lt;I&gt;Populus deltoides&lt;/I&gt; Bartr.) Phloem Sap Content Caused by Leaf Development May Affect Feeding Site Selection Behavior of the Aphid, &lt;I&gt;Chaitophorous populicola&lt;/I&gt; Thomas (Homoptera: Aphididae)

Apterous populations of Chaitophorous populicola Thomas (Homoptera: Aphididae) appear to track Eastern cottonwood (Populus deltoides Bartr.) leaf development. Few aphids occur on mature leaves. Marked individual aphids on leaves of different developmental stages were observed through a period of new leaf initiation. Nymph and adult C. populicola frequently track leaf development by moving up to younger leaves. A comparison of phloem sap constituents and leaf toughness among leaf developmental stages revealed some differences that could be used by C. populicola to determine leaf age. Phloem sap exudates, collected from P. deltoides leaves of different developmental stages, were analyzed by high-performance liquid chromatography for free amino acids and the phenolic glycoside salicin. Sucrose concentration in exudates, indicative of phloem sap exudation rate, was uniform among leaf stages. Of 20 amino acids examined, only aspartic acid and gamma-amino-n-butyric acid (GABA) concentrations differed significantly between leaf stages. Forward stepwise discriminant function analysis showed that seven of the amino acids analyzed are useful for classifying leaf maturity groupings. Aphid-infested cottonwoods had lower cystine concentrations in phloem sap than aphid-free plants. Salicin concentration was significantly higher in new leaves. Leaf toughness was assessed by lignin density and distance measurements in petiole cross-sections. Rapidly expanding leaves had significantly less lignification and new leaves had shorter distances to the vascular bundles than senescent leaves. These physiological and phytochemical differences among P. deltoides leaf developmental stages may contribute to the leaf stage selection patterns exhibited by the aphid, C. populicola.

Plant‐mediated indirect effects of carpenterworms on the insect communities attracted to fermented tree sap

AbstractCarpenterworm (Lepidoptera, Cossidae) larvae bore into trunks of the oak Quercus acutissima, thereby promoting sap exudation, and prey on insects attracted to tree sap. We examined the interactions between carpenterworms and sap‐attracted insects to elucidate community‐level consequences of carpenterworms and to estimate the relative magnitudes of their direct and indirect effects on community structure. Species richness, total abundance, and Simpson's index of diversity (1/D) in tree sap communities were all significantly higher in carpenterworm‐associated patches (sap‐exuding patches that contained either larvae or larval nests) than in patches without evidence of carpenterworms. Abundance was also significantly higher in carpenterworm‐associated patches for 10 out of 14 taxonomic groups, and this difference was much greater in the following groups that are sensitive to resource increases: drosophilid flies (Drosophilidae), sap beetles (Nitidulidae), and rove beetles (Staphylinidae). These results indicate that carpenterworms increase community size indirectly by increasing resource abundance, which is supported by the results of structural equation modeling (SEM). SEM also revealed that the direct effect of carpenterworms on species richness was weaker than their indirect effect, suggesting that predation by carpenterworms does not determine community structure. Similarly, carpenterworms can increase the abundance of some taxa by increasing resource abundance, and the predation pressure from carpenterworms on most taxa may be minor.