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Abstract. Light gradients were measured and correlated with chlorophyll concentration and anatomy of leaves in spinach (Spinacia oleracea L.). Light gradients were measured at 450, 550 and 680 nm within thin (455 μm) and thick (630 μm) leaves of spinach grown under sun and shade conditions. The light gradients were relatively steep in both types of leaves and 90% of the light at 450 and 680 nm was absorbed by the initial 140 μm of the palisade. In general, blue light was depleted faster than red light which, in turn was depleted faster than green light. Light penetrated further into the thicker palisade of sun leaves in comparison to the shade leaves. The distance that blue light at 450 nm travelled before it became 90% depleted was 120 μm in sun leaves versus 76 μm in shade leaves. Red light at 680 nm and green light at 550 nm travelled further but the trends were similar to that measured at 450nm. The steeper light gradients within the palisade‐of shade leaves were caused by increased scattering of light within the intercellular air spaces and/or cells which were less compact than those in sun leaves. The decline in the amount of light within the leaf appeared to be balanced by a gradient in chlorophyll concentration measured in paradermal sections. Progressing from the adaxial epidermis, chlorophyll content increased through the palisade and then declined through the spongy mesophyll. Chlorophyll content was similar in the palisade of both sun and shade leaves. Chloroplast distribution within both sun and shade leaves was relatively uniform so that the chlorophyll gradient appeared to be caused by greater amounts of chlorophyll within chloroplasts located deeper within the leaf. These results indicate that the anatomy of the palisade may be of special importance for controlling the penetration of photo‐synthetically active radiation into the leaf. Changing the structural characteristics of individual palisade cells or their arrangement may be an adaptation that maximizes the absorption of light in leaves with varying mesophyll thickness due to different ambient light regimes.

Water movement to and from a root depends on the soil hydraulic conductivity coefficient (L^n), the distance across any rootsoil air gap, and the hydraulic conductivity coefficient of the root (Lp). After analytical equations for the effective conductance of each part of the pathway are developed, the influences of soil drying on the soil water potential and L Kll are described during a 30 d period for a loamy sand in the field. The influences of soil drying on Lp for three desert succulents, Agave deserti, Ferocactus acanthodes, and Opuntia ficus-indica, are also described for a 30 d period. To quantify the effects of soil drying on the development of a root-soil air gap, diameters of 6-week-old roots of the three species were determined at constant water vapour potentials of -1-0 MPa and -10 MPa as well as with the water vapour potential decreasing at the same rate as soil drying during a 30 d period. The shrinkage observed for roots initially 20mm in diameter averaged 19% during the 30d period. The predominant limiting factor for water movement was L r of the root for the first 7 d of soil drying, the root-soil air gap for the next 13 d, and L Kll thereafter. Compared with the ease of water uptake from a wet soil, the decrease in conductances during soil drying, especially the decrease in L Kil , caused the overall conductance to decrease by 3 x lO^-fold during the 30 d period for the three species considered, so relatively little water was lost to the dry soil. Such rectifier-like behaviour of water movement in the soil-root system resulted primarily from changes in L^n and, presumably, is a general phenomenon among plants, preventing water loss during drought but facilitating water uptake after rainfall.

BackgroundThis study aims to analyze the computed tomography (CT) and magnetic resonance imaging(MRI) characteristics of hepatic epithelioid hemangioendothelioma (HEHE).MethodsEleven patients with histopathologically confirmed HEHE via surgical excision or biopsy were included. Imaging findings of these 11 patients were retrospectively analyzed (CT images obtained from all patients and MR images from five patients). Patterns of growth, characteristics of distribution, density/signal features, patterns of contrast enhancement, and changes of adjacent tissues were evaluated.ResultsHEHE is characterized by multiple lesions in the liver. HEHE could be further categorized as three types when considering patterns of growth: nodular type(5 cases), coalescent type(1 case) and mixed type(5 cases). In this study, a total of 312 lesions were detected, 214(74.3 %) of which were subcapsular. All lesions appeared as hypodense while round lower density were found within 10 lesions(<2 cm) on unenhanced CT images. On MRI, all lesions demonstrated low signal intensity on T1 weighted images and high heterogeneous signal intensity on T2 weighted images when compared to the normal liver parenchyma. Other imaging features included “lollipop sign”(6 cases) and capsular retraction(6 cases). On contrast-enhanced CT and MRI, lesions smaller than 2.0 cm mostly showed mild homogeneous enhancement (214/227, 94.3 %); lesions measuring 2.0–3.0 cm in diameter showed ring-like enhancement (16/53,30.2 %) and heterogeneous delayed enhancement (29/53,54.7 %); lesions larger than 3.0 cm demonstrated heterogeneous delayed enhancement (26/32, 81.3 %).ConclusionThe imaging findings of HEHE showed some typical imaging features and size-dependent patterns with contrast enhancement on both CT and MR images, these features can be used for accurate imaging diagnosis of HEHE.

CO, uptake, water vapor conductance, and biomass production of Opuntia ficus-indica, a Crassulacean acid metabolism species, were studied at CO, concentrations of 370, 520, and 720 pL 1-' in open-top chambers during a 23-week period. Nine weeks after planting, daily net CO, uptake for basal cladodes at 520 and 720 pL L-' of CO, was 76 and 98% higher, respectively, than at 370 p L 1-'. Eight weeks after daughter cladodes emerged, their daily net CO, uptake was 35 and 49% higher at 520 and 720 pL L-' of COZ, respectively, than at 370 ML 1-'. Daily water-use efficiency was 88% higher under elevated C O , for basal cladodes and 57% higher for daughter cladodes. l h e daily net COz uptake capacity for basal cladodes increased for 4 weeks after planting and then remained fairly constant, whereas for daughter cladodes, it increased with cladode age, became maximal at 8 to 14 weeks, and then declined. l h e percentage enhancement in daily net C O , uptake caused by elevated COz was greatest initially for basal cladodes and at 8 to 14 weeks for daughter cladodes. l h e chlorophyll content per unit fresh weight of chlorenchyma for daughter cladodes at 8 weeks was 19 and 62% lower in 520 and 720 p L 1-' of COz, respectively, compared with 370 pL L-'. Despite the reduced chlorophyll content, plant biomass production during 23 weeks in 520 and 720 p L 1-' of CO, was 21 and 55% higher, respectively, than at 370 pL 1-l.The root dry weight nearly tripled as the CO, concentration was doubled, causing the root/shoot ratio to increase with CO, concentration. During the 23-week period, elevated COz significantly increased COZ uptake and biomass production of O. ficus-indica.