Effects of shade treatments on the photosynthetic capacity,chlorophyll fluorescence,and chlorophyll content of Tetrastigma hemsleyanum Diels et Gilg

Tetrastigma hemsleyanum Diels et Gilg was grown under full sunlight and moderate and high levels of shade for one month to evaluate its photosynthetic and chlorophyll fluorescence response to different light conditions. The results showed that T. hemsleyanum attained greatest leaf size and P_n when cultivated with 67% shade. Leaves of seedlings grown with 90% shade were the smallest. Leaf color of plants grown under full sunlight and 50% shade was yellowish-green. The P_n value increased rapidly as PPFD increased to 200 μmol m^?2 s^?1 and then increased slowly to a maximum, followed by a slow decrease as PPFD was increased to 1000 μmol m^?2 s^?1. P_n was highest for the 67% shade treatment and the LSP for this shade treatment was 600 μmol m^?2 s^?1. Full sunlight and 50% shade treatments resulted in significant reduction of ETR and qP and increased NPQ. Chl a, Chl b and total chlorophyll content increased and Chl a/b values decreased with increased shading. Results showed that light intensity greater than that of 50% shade depressed photosynthetic activity and T. hemsleyanum growth. Irradiance less than that of 75% shade limited carbon assimilation and led to decreased plant growth. Approximately 67% shade is suggested to be the optimum light irradiance condition for T. hemsleyanum cultivation.     

Intraspecific competition and light effect on reproduction of Ligularia virgaurea,an invasive native alpine grassland clonal herb

The relationship between sexual reproduction and clonal growth in clonal plants often shows up at the ramet level. However, only a few studies focus on the relationship at the genet level, which could finally account for evolution. The sexual reproduction and clonal growth of Ligularia virgaurea, a perennial herb widely distributed in the alpine grasslands of the Qinghai‐Tibetan Plateau of China, were studied under different competition intensities and light conditions at the genet level through a potted experiment. The results showed that: (1) sexual reproduction did not depend on density or light, and increasing clonal growth with decreasing density and increasing light intensity indicated that intraspecific competition and light intensity may affect the clonal life history of L. virgaurea; (2) both sexual reproduction and clonal growth show a positive linear relationship with genet size under different densities and light conditions; (3) a threshold size is required for sexual reproduction and no evidence of a threshold size for clonal growth under different densities and light conditions; (4) light level affected the allocation of total biomass to clonal and sexual structures, with less allocation to clonal structures and more allocation to sexual structures in full sunlight than in shade; (5) light determined the onset of sexual reproduction, and the genets in the shade required a smaller threshold size for sexual reproduction to occur than the plants in full sunlight; and (6) no evidence was found of trade‐offs between clonal growth and sexual reproduction under different densities and light conditions at the genet level, and the positive correlation between two reproductive modes indicated that these are two integrated processes. Clonal growth in this species may be viewed as a growth strategy that tends to maximize genet fitness.     

Effect of drought and ABA on growth, photosynthesis and antioxidant system of Cotinus coggygria seedlings under two different light conditions

We exposed seedlings of Cotinus coggygria var. cinerea to drought and exogenous abscisic acid (ABA) under two different light conditions. Two watering regimes (well-watered and drought), two exogenous ABA applications (no ABA and with ABA) and two light regimes (full sunlight and shade) were employed. Compared with well-watered treatment, drought treatment significantly reduced the relative growth rate, relative water content (RWC), net photosynthesis rate (A) and transpiration (E), but increased chlorophyll a (chla), carbon isotope (δ¹³C), endogenous ABA, malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) contents, and guaiacol peroxidase (POD) and catalase (CAT) activities. There was an apparent alleviation of drought effects by shade, as indicated by the lower relative growth rate, and chlorophyll, MDA and H₂O₂ contents, and increases in indoleacetic acid (IAA) and reduced glutathione (GSH) contents. On the other hand, the exogenous ABA application under shade induced protective effects on drought-stressed seedlings, as visible in RWC, MDA, A, stomatal conductance (g_s), E, δ¹³C, ABA and IAA values. In all, our results suggest that seedlings of C. coggygria are more sensitive to drought under full-light than under shade.     

Optimization of cultivation conditions for fatty acid composition and EPA production in the eustigmatophycean microalga Trachydiscus minutus

We determined the effects of cultivation conditions (nitrogen source, salinity, light intensity, temperature) on the composition of polyunsaturated fatty acids (PUFAs) and the production of eicosapentaenoic acid (EPA) in the laboratory cultured eustigmatophycean microalga, Trachydiscus minutus. T. minutus was capable of utilizing all nitrogen compounds tested (potassium nitrate, urea, ammonium nitrate, ammonium carbonate) with no differences in growth and only minor differences in fatty acid (FA) compositions. Ammonium carbonate was the least appropriate for lipid content and EPA production, while urea was as suitable as nitrates. Salinity (0.2 % NaCl) slightly stimulated EPA content and inhibited growth. Increasing salinity had a marked inhibitory effect on growth and PUFA composition; salinity at or above 0.8 % NaCl was lethal. Both light intensity and temperature had a distinct effect on growth and FA composition. The microalga grew best at light intensities of 470–1,070 μmol photons m^?2 s^?1 compared to 100 μmol photons m^?2 s^?1, and at 28 °C; sub-optimal temperatures (20, 33 °C) strongly inhibited growth. Saturated fatty acids increased with light intensity and temperature, whereas the reverse trend was found for PUFAs. Although the highest level of EPA (as a proportion of total FAs) was achieved at a light intensity of 100 μmol photons m^?2 s^?1 (51.1?± 2.8 %) and a temperature of 20 °C (50.9?±?0.8 %), the highest EPA productivity of about 30 mg L^?1?day^?1 was found in microalgae grown at higher light intensities, at 28 °C. Overall, for overproduction of EPA in microalgae, we propose that outdoor cultivation be used under conditions of a temperate climatic zone in summer, using urea as a nitrogen source.     

Use of a SPAD meter to estimate chlorophyll content in Eugenia uniflora L. leaves as affected by contrasting light environments and soil flooding

In three separate experiments, the effectiveness of a SPAD-502 portable chlorophyll (Chl) meter was evaluated for estimating Chl content in leaves of Eugenia uniflora seedlings in different light environments and subjected to soil flooding. In the first experiment, plants were grown in partial or full sunlight. In the second experiment plants were grown in full sunlight for six months and then transferred to partial sunlight or kept in full sunlight. In the third experiment plants were grown in a shade house (40% of full sunlight) for six months and then transferred to partial shade (25–30% of full sunlight) or full sunlight. In each experiment, plants in each light environment were either flooded or not flooded. Non-linear regression models were used to relate SPAD values to leaf Chl content using a combination of the data obtained from all three experiments. There were no significant effects of flooding treatments or interactions between light and flooding treatments on any variable analyzed. Light environment significantly affected SPAD values, chlorophyll a (Chl a), chlorophyll b (Chl b), and total chlorophyll [Chl (a+b)] contents in Experiment I (p≤0.01) and Experiment III (p≤0.05). The relationships between SPAD values and Chl contents were very similar among the three experiments and did not appear to be influenced by light or flooding treatments. There were high positive exponential relationships between SPAD values and Chl (a+b), Chl a, and Chl b contents.     

Light-Induced Adaptive Responses under Greenhouse and Controlled Conditions in the Fern Pteris cretica var. ouvrardii

The photosynthetic capabilities of the fern Pteris cretica var. ouvrardii were analysed by means of the light response curves of CO₂ exchange. In control growth conditions (greenhouse, low-light: 20–32 W m^?2); photosynthesis was shown to be saturated for low irradiance (20–25 W m^?2); the saturating photosynthetic rate, very low as compared to higher plants, was due to an extremely high intracellular resistance. When irradiance during the photosynthesis measurement was higher than 60–80 W m^?2, a constant decline of net CO₂ exchange as a function of time was observed. When irradiance during growth was enhanced, whether in greenhouse (20–250 W m^?2) or controlled (62 W m^?2) conditions, the first fronds that had developed in the new condition from the crosier stage exhibited decreased net maximal photosynthesis and a decreased efficiency in low light, but saturating irradiance was unmodified. However, the fronds whose entire differentiation (from meristem) occurred under these moderate irradiances (plants defoliated of all fronds and crosiers at the time of transfer), possessed more efficient photosynthetic characteristics than control plants. Pteris is able to grow under extreme shade conditions (4–8 W m^?2); light saturating photosynthesis and efficiency are higher under extreme shade than under control conditions. These adaptive characteristics indicate that Pteris is a well-adapted shade species.     

Positive effects of ectomycorrhizal colonization on growth of seedlings of a tropical tree across a range of forest floor light conditions

In a shadehouse experiment we tested the effects of light, nutrients and ectomycorrhizal fungi (EMF) on the growth of Vatica albiramis van Slooten (Dipterocarpaceae) seedlings. We hypothesised that it is more advantageous for plants to form connections with EMF and to trade carbon for nutrients with EMF under high light than low light. The relationship between seedling growth and the proportion of ectomycorrhizal root tips was expected as positive in high light and as negative in low light. Light conditions simulated the forest understory (low; 3% full sunlight), a small gap (medium; 11%) and a large gap (high; 33%) and a fully factorial combination of nutrients (F?/+) and ectomycorrhizal colonization (EMF?/+) treatments were applied within light conditions. The application of EMF and nutrients did significantly alter seedling growth across the range of forest floor light conditions, however the key hypothesis was rejected as seedling growth under low light was not affected by increased EMF colonization of root tips (light:EMF colonization χ²?=?2.97, p?=?0.23). In addition, the lack of difference in morphotype abundance across light conditions indicated that light changes may not favour the association to specific EMF in seedlings of this particular dipterocarp species. Our results suggest that antagonistic (non-beneficial to the plant) effects due to ectomycorrhizal colonization under a light constrained environment may not affect seedling growth of Vatica albiramis.     

The effect of shading on photosynthesis,growth, and regrowth following defoliation for Bromus tectorum

Summary The effect of full sunlight, 60%, or 90% attenuated light on photosynthetic rate, growth, leaf morphology, dry weight allocation patterns, phenology, and tolerance to clipping was examined in the glasshouse for steppe populations of the introduced grass, Bromus tectorum. The net photosynthetic response to light for plants grown in shade was comparable to responses for plants grown in full sunlight. Plants grown in full sunlight produced more biomass, tillers and leaves, and allocated a larger proportion of their total production to roots than plants grown in shade. The accumulation of root and shoot biomass over the first two months of seedling growth was primarily responsible for the larger size at harvest of plants grown in full sunlight. Plants grown under 60% and 90% shade flowered an average of 2 and 6 weeks later, respectively, than plants grown in full sunlight. Regrowth after clipping was greater for plants grown in full sunlight compared to those grown in shade. Even a one-time clipping delayed flowering and seed maturation; the older the individual when leaf area was removed, the greater the delay in its phenology. Repeated removal of leaf area was more frequently fatal for plants in shade than in full sunlight. For plants originally grown in full sunlight, regrowth in the dark was greater than for shaded plants and was more closely correlated to non-flowering tiller number than to plant size. This correlation suggests that etiolated regrowth is more likely regulated by the number of functional meristems than by differences in the size of carbohydrate pools. Thus, shading reduces the rate of growth, number of tillers, and ability to replace leaf area lost to herbivory for B. tectorum. These responses, in turn, intensify the effect of competition and defoliation for this grass in forests. B. tectorum is largely restricted to forest gaps at least in part because of its inability to acclimate photosynthetically, the influence of shade on resource allocation, and the role of herbivory in exacerbating these effects.     

Growing microalgae as aquaculture feeds on twin-layers: a novel solid-state photobioreactor

Four strains of marine microalgae commonly used as live feeds in hatcheries (Isochrysis sp. T.ISO, Tetraselmis suecica, Phaeodactylum tricornutum, Nannochloropsis sp.) were grown in a novel solid-state photobioreactor, the twin-layer system. Microalgae were immobilized by self adhesion to vertically oriented twin-layer modules which consisted of two different types of ultrathin layers, a macroporous source layer (glass fiber nonwoven) through which the culture medium was transported by gravity flow, and a microporous substrate layer (plain printing paper) which carried the algae on both surfaces of the source layer. This simple open cultivation system effectively separated the immobilized microalgae from the bulk of the growth medium and permitted prolonged cultivation of microalgae with average biomass yields of 10–15 g dry weight m^?2 growth area after 14–25 days of cultivation. Algal biomass was harvested as fresh weight (with 72–84 % water content) without the need to pre-concentrate algae. No aeration or external CO₂ supply was necessary, and due to the microporous substrate layer, no eukaryotic contaminations were observed during the experiment. All experiments were conducted in Germany under greenhouse conditions with natural sunlight. Small-scale growth experiments performed under the same conditions revealed that growth over most of the experimental period (24 days) was linear in all tested algae with growth rates (dry weight per square meter growth area) determined to be 0.6 g ?m^?2?day^?1 (Isochrysis), 0.8 g? m^?2?day^?1 (Nannochloropsis), 1.5 g ?m^?2?day^?1 (Tetraselmis), and 1.8 g? m^?2?day^?1 (Phaeodactylum). Due to its cost-effective construction and with further optimisation of design and productivity at technical scales, the twin-layer system may provide an attractive alternative to methods traditionally used to cultivate live microalgae.     

Life history and population dynamics of the Japanese Yam,Dioscorea japonica Thunb.

The adaptive significance of the emergence mode ofDioscorea japonica was studied with respect to initial plant size (seed, bulbil and tuber) and light intensity, using mathematical simulation based on Yokoi's (1976) model. Under 1.5% full sunlight conditions, plants emerging with only one leaf did not develop a shoot system throughout the growing period (Hori and Oshima, 1986). Simulation indicated that, for this species of plant under poor productive conditions, the optimal time for switch-over from the vegetative to reproductive growth phase to maximize the tuber weight at the end of the growing period, occurred immediately following the start of autotrophic growth. By means of shoot growth patterns, small and large size plants acquired the ability of shade tolerance and shade avoidance, respectively. Further, the life history ofD. japonica could be expressed as a flow chart based on plant size and light intensity data.     

Photomorphogenesis in <Emphasis Type="Italic">Dracaena draco</Emphasis>

Key message

Sunlight is a key environmental factor in growth, flowering and shaping of the Dracaena draco tree. Unidirectional light deforms the tree and may cause it to tilt.

Abstract

Dracaena draco, a tree-like monocot, lives in cycles of vegetative growth and flowering. The cycles, as well as the tree growth form, are under genetic control. What controls their length has been unknown before. We propose that it is sunlight. Our trees of the same origin, growing for 20 years in the garden in varying sunlight conditions, started to flower when 9–12, 16 and 18–19 years old, for those growing in full sun, part shade and shade, respectively. In full sun, they grow shorter trunks than those in shade, catching overhead sun. Their branches also had shorter or longer growth and flowering cycles depending on sunlight availability. D. draco tree exhibited strong phototropic response and its crown was organized by the direction of growing tips. In full and in overhead sun, it had a regular form but asymmetrical in unidirectional, oblique sunlight. An asymmetrical crown and the absence of reaction wood may cause the D. draco tree tilting and progressive loss of balance.

     

Light quality and quantity regulate aerobic methane emissions from plants

Studies have been mounting in support of the finding that plants release aerobic methane (CH₄), and that these emissions are increased by both short‐term and long‐term environmental stress. It remains unknown whether or not they are affected by variation in light quantity and quality, whether emissions change over time, and whether they are influenced by physiological parameters. Light is the primary energy source of plants, and therefore an important regulator of plant growth and development. Both shade‐intolerant sunflower and shade‐tolerant chrysanthemum were investigated for the release of aerobic CH₄ emissions, using either low or high light intensity, and varying light quality, including control, low or normal red:far‐red ratio (R:FR), and low or high levels of blue, to discern the relationship between light and CH₄ emissions. It was found that low levels of light act as an environmental stress, facilitating CH₄ release from both species. R:FR and blue lights increased emissions under low light, but the results varied with species, providing evidence that both light quantity and quality regulate CH₄ emissions. Emission rates of 6.79–41.13 ng g^?1 DW h^?1 and 18.53–180.25 ng g^?1 DW h^?1 were observed for sunflower and chrysanthemum, respectively. Moreover, emissions decreased with age as plants acclimated to environmental conditions. Since effects were similar in both species, there may be a common trend among a number of shade‐tolerant and shade‐intolerant species. Light quantity and quality are influenced by factors including cloud covering, so it is important to know how plants will be affected in the context of aerobic CH₄ emissions.     

Effects of light intensity on the growth and buoyancy of detachedElodea nuttallii (Planch.) St. John during winter

The influences of light intensity on the growth and buoyancy of detachedElodea muttallii (Planch.) St. John during winter were examined under controlled experimental light conditions. Light was controlled by mesh-screens at five levels ranging between 0.3 and 51% of the aerial full sunlight in an outdoor pond. Growth of detached segments was compared with respect to shoot and root lengths, dry weight and starch content in tissues. Buoyancy of segments at each light level was evaluated by percentage frequency of floating segments. Critical light intensity for the winter growth was estimated as ca. 4.5% of the aerial full sunlight. Most segments at light levels lower than 4.5% had been floating in water since the early period of the experiment, while all segments at light levels higher than 17% had been sinking to the bottom until water temperature became higher than 10 C. The data on segment buoyancy and tissue analysis for starch content showed an inverse relationship between percentage frequency of floating segments and starch content in tissues. These results suggest that detached segments in nature could escape from the photosynthetically unsuitable regions by reduced specific gravity caused by the consumption of starch, and establish themselves only if they could arrive at a safe-site where light conditions are sufficient to accumulate photosynthate.     

Seasonal trends in morpho-physiological attributes and bioactive content of Valeriana jatamansi Jones under full sunlight and shade conditions

Valeriana jatamansi Jones, an important medicinal herb of the Himalayan region, is an essential source of many therapeutic compounds and is traded/consumed in very high volume. The hypothesis of this study was that different seasons and light conditions may affect the content of medicinally valuable components with changes in the morpho-physiological attributes of the plant. Growing plants under suitable light conditions and harvesting of appropriate plant parts in optimum season is crucial for harnessing the full potential of the crop. Thus, the study was carried out to determine the seasonal response of V. jatamansi plants (genetically identical plants of same age) in terms of growth and phytochemical content under two different light conditions (full sunlight and 50% shade). During all seasons, growth parameters (plant height, leaf number, leaf area, relative water content, plant biomass) and the principle bioactive compounds (valerenic acid) were higher under shade conditions, while total flavonoids, tannins, phenolic compounds and antioxidant activities were higher under full sunlight conditions. HPLC analysis revealed that valerenic acid and most of the phenolic content were higher during summer season, especially in leaf part of the plant. The study suggested harvesting of V. jatamansi plants (especially leaf), during summer season to harness high quality raw material and to prevent loss of belowground parts. This strategy can be adopted by farmers for large scale cultivation of species.Supplementary InformationThe online version of this article contains supplementary material available at 10.1007/s12298-021-00944-0     

Does shading explain variation in morphophysiological traits of tropical epiphytic orchids grown in artificial conditions?

Light is one of the main factors of physical environment and it controls plant growth and development by interfering with photosynthesis, especially concerning CO₂ assimilation. Photosynthetic characteristics and growth of C3 epiphytic orchids Miltonia flavescens and Miltonia spectabilis var. moreliana were analyzed under four radiation regimens (25, 50 and 75?% of global radiation and full sunlight). Anatomical characterizations were performed on plants grown at 25?% shade. Artificial shading was obtained using different shading nylon nets. The highest values of light-saturated photosynthetic, dark respiration, net photosynthetic and leaf transpiration rates, stomatal conductance and intercellular to atmospheric CO₂ concentration ratio were observed at full sunlight and 25?% shade. Moreover, both species allocated greater amount of leaf dry weight in those treatments. On the other hand, it was observed a greater investment in pseudobulb biomass in more shaded conditions (50 and 75?%), corroborating with the highest values of intrinsic water-use efficiency observed in those treatments. It was found a significant effect of shading on leaf area and specific leaf area. The anatomical features reflected strategies to save water. The phenotypic plasticity and principal component analysis suggested that the physiological traits were more responsive to light levels than the morphological traits. The results indicate that those species appear to be adapted to high irradiances conditions and are capable of adjusting, via morphophysiological changes, to light availability.     

Morphological and biomass characteristic acclimation of trident maple (Acer buergerianum Miq.) in response to light and water stress

Acer buergerianum Miq. (Trident maple) is a native species of China with a large distribution, but exist in small population. Water and light are two important factors limiting plant growth and are crucial in the framework of forest regeneration. However, there is no consensus on how shade interacts with drought. Four hypotheses in the recent literature variously predict that shade will have a stronger, weaker or equal impact on seedlings under drought stress. This study investigated the interactive responses of A. buergerianum to light and water focusing on seedling growth, leaf morphology and biomass partitioning by performing a growth experiment in pots with different water supply regimes [15, 35, 55, 75, 95 % of field capacity (FC)] combined with two light regimes (10 and 66 % of full sunlight). After 123 days treatment, the results showed that shade greatly reduced growth and biomass, in contrast enhancing the amount of chlorophyll, the amount of water in the leaves, and the specific leaf area. Drought reduced growth, biomass, and the bulk of the leaves. Most leaf traits and biomass characteristics had strong interactions in their responses to light and water treatments. Allometric analysis revealed that water and light had no effects on root to shoot ratios, main root to lateral root ratios, and root mass ratios. Shade alleviated the negative impact of drought. A. buergerianum successfully adapted to the various light and water conditions. We recommend a water supply above 15 % FC to keep the seedlings vigorous, under both sunlight conditions.     

Drought-Responsive Gene Expression in Sun and Shade Plants of <Emphasis Type="Italic">Haberlea rhodopensis</Emphasis> Under Controlled Environment

Haberlea rhodopensis is a homoiochlorophyllous desiccation-tolerant plant growing mostly in shaded rock rifts below the trees at very low light intensity. These shade plants are very sensitive to photoinhibition and do not survive desiccation at irradiance of 350 μmol m^?2 s^?1, whereas plants growing on the top of rocks exposed to full sunlight (sun plants) can survive at even higher light intensities regularly. The aim of the present study was to establish how acclimation to different light intensities influences the expression of selected drought-responsive genes and the physiological activity during desiccation of shade and sun plants under controlled culture conditions. The photosynthetic activity was higher in sun plants not only when fully hydrated but also during dehydration. Thus, the higher photosynthetic capacity, reflected in PSII but especially in PSI activity, is accompanied by a reduced susceptibility to photodamage. For most of the genes examined, drought was the main factor in regulation; in addition, some were light modulated like genes coding for putative superoxide dismutase (SOD), ascorbate peroxidase (APX) and thioredoxin (TRX), whereby the former was almost purely light regulated. Differences between sun and shade plants concerned mainly on the time course. Whereas some genes reacted already at moderate desiccation only in sun plants (genes for monodehydroascorbate reductase (MDAR), plastidic translocase (PTL) similar to OEP16 and one of the genes, newly annotated ELIP-like, specific for H. rhodopensis), especially a gene for a putative UDP-glucuronic acid decarboxylase (UDP) retained its enhanced expression longer during recovery. Thus, these genes are probably especially important for survival and recovery in sun plants.     

二年生三七农艺和质量性状对环境光强的响应特征

为探究光照强度对二年生三七(Panax notoginseng)农艺性状和质量性状的影响,采用人工遮荫的方法,对三七植株的农艺性状、解剖结构、生物量和皂苷含量进行研究。结果表明,三七生物量积累以透光率为13.5%时最大;三七总皂苷含量在透光率9.2%时最高,透光率为13.5%时单株皂苷含量较大。当透光率降低,三七的叶片和茎部生物量增加;透光率增加时,三七通过增加叶片上表皮厚度、海绵组织厚度、栅栏组织厚度和叶片厚度来减少光捕获。因此,在透光率为9.2%~13.5%时对三七的生长、生物量及皂苷的积累有促进作用。     

Seasonal plasticity of Ludwigia grandiflora under light and water depth gradients: An outdoor mesocosm experiment

Abiotic factors in the introduced area can limit the establishment of exotic species. Adaptation to new abiotic parameters through plastic responses is important for their establishment and distribution pattern. Survival and growth of exotic hydrophytes are related to their plasticity and their ability to adapt to local conditions. Light and water depth are two of the predominant factors determining survival, growth, distribution and abundance of aquatic plants. Although many studies have been carried out on the effect of water level and light on plant performance, their potential interactions are poorly understood. Here, we carried out an outdoor mesocosm experiment, in order to test the role of water depth, light intensity and their potential interactions on the growth and vigour of the invasive macrophyte species Ludwigia grandiflora. Three light intensities (100%, 70% and 50% of sunlight) and three water depths (30, 50 and 80 cm) were tested over a 6-week period, in spring, summer and autumn 2011. We showed that the mortality, biomass, apical and lateral growth of L. grandiflora, as well as its biomass allocation, varied according to the season and responded to both light intensity and water depth. Interactions between water depth and light intensity can have an amplifying effect on the growth of L. grandiflora. Similarities between shade and deep water adaptation responses were observed. A higher biomass and a high morphological plasticity in response to these factors were found particularly at the beginning of the life cycle. Although the invasive amphibious L. grandiflora shows a high tolerance to different water levels and light intensities, the optimal growth conditions for L. grandiflora in our experiment seem to be under full sunlight and in 30 cm of water. Colonization of light or low shade aquatic habitats, as well as shallow environments, can occur due to the high plasticity of L. grandiflora. These results may be important relative to increasing level of water bodies under climatic changes.     

Growth, soluble carbohydrates, and aloin concentration of Aloe vera plants exposed to three irradiance levels

Research was conducted on Aloe vera, a traditional medicinal plant, to investigate the effects of light on growth, carbon allocation, and the concentrations of organic solutes, including soluble carbohydrates and aloin. The plants were vegetatively propagated and grown under three irradiances: full sunlight, partial (30% full sunlight), and deep shade (10% full sunlight) for 12-18 months. After 1 year of growth, five plants from each treatment were harvested to determine total above- and below ground dry mass. Four plants from the full sunlight and the partial shade treatments were harvested after 18 months to assess the soluble carbohydrate, organic acid and aloin concentrations of the clear parenchyma gel and the yellow leaf exudate, separately. Plants grown under full sunlight produced more numerous and larger axillary shoots, resulting in twice the total dry mass than those grown under partial shade. The dry mass of the plants grown under deep shade was 8.6% that of plants grown under full sunlight. Partial shade increased the number and length of leaves produced on the primary shoot, but leaf dry mass was still reduced to 66% of that in full sunlight. In contrast, partial and deep shade reduced root dry mass to 28 and 13%, respectively, of that under full sunlight, indicating that carbon allocation to roots was restricted under low light conditions. When plants were sampled 6 months later, there were only minor treatment effects on the concentration of soluble carbohydrates and aloin in the leaf exudate and gel. Soluble carbohydrate concentrations were greater in the gel than in the exudate, with glucose the most abundant soluble carbohydrate. Aloin was present only in the leaf exudate and higher irradiance did not induce a higher concentration. Limitation in light availability primarily affected total dry mass production and allocation, without substantial effects on either primary or secondary carbon metabolites.