Influence Of Light Regimes Research Articles

Basil and Lettuce Microgreens Production in Low-Cost Hydroponic Installations, under Operational and Semi-Controlled Conditions

Microgreens produced hydroponically at home, represent a solution of the future due to the advantages it has. The purpose of this research is to analyze certain elements relevant for the microgreens crop (basil and lettuce), simultaneously, in identical low-cost hydroponic platforms, in operational (common spaces) and semi-controlled conditions (plant growing tent). The obtained results were analyzed, both from the point of view of the growing conditions and the influence of light regimes, as well as the development of seedlings, production (fresh weight and dry weight) and quality (total phenolic) of the microgreens. In operational environmental conditions there is a higher variation of the environmental parameters, compared to the semi-controlled environment, but the oscillation of natural light seems to have a better influence on the development of microgreens. Internode length in operational environmental conditions varies for basil between 25.2-35.2 mm, for lettuce between 31.9-32.8 mm, and in semi-controlled environmental conditions, it varies for basil between 25.2-32.1 mm and for lettuce between 30.2-31.9 mm. In semi-controlled conditions, the average fresh weight production achieved by the two species (and four varieties) is 734.73 g m-2 for basil, 809.56 g m-2 for lettuce, and represents 823.74 g m-2 for basil, 777.61 g m-2 for lettuce in operational environmental conditions. The variability of the data recorded for total phenols is very high. Lettuce contains 98-107.33 mg kg-1, and basil 107.67-186.33 mg kg-1 total phenols. Feedback from these tests will be used for final validation of the low-cost hydroponic platform components.

Influence of light regime on the performance of an immobilised microalgae reactor for wastewater nutrient removal

Microalgae immobilised within a resin shaped into beads have demonstrated the ability to remediate nutrients from wastewater effluents within hydraulic retention times as low as 3h. Methods to further optimise performance consider parameters relating to the bead with the impact of external conditions seldom investigated. Light is an essential parameter for microalgal growth with its effect on suspended cultures well documented. This work explores the influence of light on nutrient remediation by immobilised microalgae in order to recommend an optimal lighting solution for an immobilised microalgae technology based on Scenedesmus obliquus encapsulated within calcium-alginate beads. White light (400–700nm) at a photon flux density (PFD) of 200μmol∙m−2∙s−1 was determined optimal when illuminating a packed bed configuration. When considering phosphate, these conditions supported a remediation rate of 10.7 (± 0.01) mgP∙h−1∙106 beads−1 in comparison to 10.2 (± 0.01) and 10.1 (± 0.01) mgP∙h−1∙106 beads−1 for the blue (465nm) and red (660nm) spectra respectively. Although similar performance was demonstrated, light transmission trials determined white light to penetrate to greater bed depths resulting in a larger photoactive zone. A PFD of 200μmol∙m−2∙s−1 was regarded as optimal when considering performance, attenuation depth and effective use of total supplied light. In addition, photoperiods trials determined lighting periods <12h extended the overall treatment time.

The influence of light regime on the growth data and pigment composition of the plant Gentiana lutea cultured in vitro

New technologies of reintroduction of plant species presuppose implementing both traditional and biotechnological methods for obtaining certain planting materials. However, plants cultivated in vitro exist in specific conditions that lead to changes in their structural and functional state. This explains why it is hard for them to adapt to ex vitro and in situ conditions. Therefore, there is a need for the development of a multistage method of cultivating in vitro plants that would make the influence on their adaptive mechanism in ex vitro and in situ conditions possible. One of its stages is the optimization of the light regime of cultivation which can both initiate the change of the state of the photosynthetic apparatus of plants and increase their bioproductivity stimulating the work of their protective system. This work studies changes in the morphogenesis, growth data and pigment composition of the rare species of Gentiana lutea L. of three populations in the Ukrainian Carpathian (mountains Pozhyzhevska and Sheshul-Pavlyk, plateau Lemska) in vitro focusing particularly on the cultivation light regime. The research has proved the inefficiency of using fluorescent lamps of daylight lamps (LD) type as source of illumination because the low intensity of luminous flux in the area of photosynthetically active radiation (PAR), as well as high proportion of wavelength of blue (400–500 nm) and green (500–600 nm) range in the spectrum cause specific reactions of photomorphogenesis, which, despite the high content of pigments in plastids, lead to poor development of root systems, stretching the stems, formation of small leaves with thin leaflet plate, generally low productivity and low adaptive potential of G. lutea plants to ex vitro and in situ conditions. Complement of cold white light lamps to the fluorescent lamps LD type in the ratio of 1 : 1 enables one to increase the intensity of illumination in the field of PAR and raise the fraction of wavelength of red range (600–700 nm). Such light conditions both improve the bio-productivity of G. lutea plants of all three populations cultured in vitro in comparison to the LD type regimen, reducing the content of chlorophyll b and carotenoids in light-harvesting complexes of photosystems and facilitate an increase in the microclonal multiplication factor without using higher concentrations of exogenous growth regulators,which significantly reduces the cost of the process of obtaining planting materials. It was proved that a combination of LD type lamps, cold white light lamps and phytolamps in the ratio 1 : 1 : 0.6 should be used on the final stages of preparation of the planting material of G. lutea before transferring it to ex vitro and in situ conditions. This relates to the fact that the increase of the wavelength of the red range results in the widening of the active surface of the leaves, rise in the content of photosynthetic pigments, and the noticeable growth of the aboveground and underground parts of the plants. The article assumes that the use of such illumination mode will ensure a faster transition of cultured in vitro G. lutea plants from heterotrophic to autotrophic nutrition, improving their adaptive potential and enabling easier adaptation to non-sterile ex vitro and in situ conditions.

THE EFFECTS OF LIGHT REGIME AND SUBSTRATE ON FLOWER PRODUCTIVITY AND LEAF MINERAL COMPOSITION IN TWO GERBERA CULTIVARS

This research evaluates the influence of light regime and substrate composition on the flower productivity and leaf macronutrient content of two gerbera cultivars (‘Ruby Red’ and ‘Vino’) grown in a greenhouse. A special emphasis was given to macro-element ratios in gerbera leaf. The results confirm positive influence of supplemental lighting on flower yield in both gerbera cultivars. Also, mixed substrate (coco fiber + rice husks) resulted with higher flower yield. Cultivar ‘Vino’ showed better productivity and significantly lower concentration of nitrogen (N), potassium (K), and magnesium (Mg) as compared to ‘Ruby Red’. The total flower productivity per plant correlated with some of the tested macronutrients in gerbera leaf (N, K, Mg) only in natural light conditions. Among all calculated leaf nutrient ratios, only P/Mg was significantly and positively correlated to flower yield, based on data from both light variants.

Effects of genotype, light regime, explant position and orientation on direct somatic embryogenesis from leaf explants of Phalaenopsis orchids

The influence of light regime, explant position and orientation on direct embryo formation from leaf explants of two Phalaenopsis, P. amabilis and P. Nebula, were investigated to optimize the protocol for regenerating of this orchid. When explants were cultured in light, direct embryogenesis was retarded in both species. Embryos showed whitish to pale green in color and larger size than those cultured in darkness. Furthermore, light regime induced explant browning, embryo necrosis and eventually low plantlet conversion rate. Sixty days of culture in darkness is the most suitable duration for direct embryo induction. Explant orientation also significantly affected direct embryo formation, and explants placed adaxial-side-up on culture medium had higher embryogenic response than abaxial-side-up orientation. In both species, the cut end had highest embryogenic competence than other parts of the explant. Moreover, when the leaf explant was cut transversely into two segments, the leaf basal segment had higher embryogenic competence than the leaf tip segment.

Effect of photoperiod manipulation on the daily rhythms of melatonin and reproductive hormones in caged European sea bass ( Dicentrarchus labrax)

Reproduction in fish is cyclical and timed to guarantee the survival of the offspring. Seasonal variations in reproductive hormones of fish have been deeply investigated in fish over the last years. However, there are few studies regarding the daily changes in reproductive hormone profiles in teleosts. The aim of the present research was to investigate the effects of photoperiod manipulation on melatonin and reproductive hormones (pituitary sbGnRH, pituitary LH and plasma LH, testosterone [T], and 11-ketotestosterone [11KT]) daily rhythms in male sea bass, kept in net cages under farming conditions in winter (9L:15D). Fish were distributed in two groups, one under constant long photoperiod (18L:6D) and the other under natural photoperiod. The photoperiod strongly influenced the daily melatonin profile, so that the duration of the nocturnal melatonin rise was longer in the control group than in the group exposed to the artificial photoperiod (18L:6D). A daily rhythm was observed in the pituitary sbGnRH profile in both groups, showing the lowest levels during the dark period. A daily rhythm of pituitary LH was detected in the control group, which was suppressed in the group under long photoperiod. Daily variations in plasma LH were observed, the highest levels being found in the dark phase in both groups, although this profile was significantly altered by artificial light, maintaining a fixed relationship between the first nocturnal rise of melatonin and the nocturnal peaks of plasma LH in both groups. Plasma T levels showed significant fluctuations in their daily cycle following a sinusoidal pattern with an acrophase around sunrise in both groups, without any influence of light regime. No significant daily variations in plasma levels of 11-KT were observed in none of the groups. Our results provide the first evidence of the presence of daily variations in pituitary sbGnRH content, pituitary and plasma LH, and plasma T in sea bass. Artificial lights suppressed the circulating melatonin and significantly affected the daily rhythm of LH storage and release.

Influence of light regimes on respiration, activity of alternative respiratory pathway and carbohydrates content in mature leaves of Ajuga reptans L.

Influence of different light regimes (plants grown in shade and in the sun) on respiration, activity of alternative respiratory pathway and carbohydrates content in mature leaves of Ajuga reptans L. was investigated. All experiments were carried out under natural conditions. Sun plants had higher respiration, activity of the alternative pathway and carbohydrates content compared to the shade plants. Additional experiments were performed in order to study effects of darkening as well as evolution of respiration and carbohydrates concentrations in leaves of A. reptans during the day. Darkening led to a decline in total respiration in all types of plants investigated. Activity of the alternative pathway remained unchanged by 20 % in the leaves of the shade plants. On the other hand, darkness led to a twofold decrease in the activity of the alternative pathway in the leaves of the sun plants. Content of soluble carbohydrates in the darkness did not change in the leaves of the shade plants while significantly decreased in the leaves of the sun plants. Total respiration in the mature leaves of the shade plants studied did not change significantly during the day. However, a significant increase in the total respiration was detected in the mature leaves of the sun plants in the evening and in the night. Activity of the alternative respiratory pathway did not change significantly in the leaves of the shade plants during the day and corresponds to ca 20 % of the total respiration. The sun plants examined exhibited significantly higher activity of the alternative pathway during the period of active photosynthesis. In general, activity of the alternative pathway varied in the sun plants between 30 and 35 % of the total respiration during the day. Content of soluble carbohydrates decreased significantly during the day in the mature leaves of the shade plants, while no statistically significant changes by the sun plants could be detected. It has been suggested that increase in respiration and activity of the alternative pathway in the sun plants tested can be controlled by the content of carbohydrates in leaves. No clear proposal could be done concerning mechanisms regulating alternative pathway activity in the shade plants of A. reptans.

Influence of light regime on nitrate reductase activity and organic and inorganic solute composition of four sedges(carexspp.)

A survey was conducted on the inorganic and organic solute patterns of plants in connection with nitrate metabolism according to different light regimes (1.9, 16.0, 91.5 ). Besides measuring in vivo NRA, we also quantitatively analyzed ater-soluble inorganic ions, organic acids, low molecular weight carbohydrates, amino aciss and total N (% DW). Among 4 Carex species, C. pilosa is known as shade-adapted species and the others as half (C. gracilis) to full (C. rostrata & C. distans) light-adapted species. Compared to species adapted to high light intensity, shade-adapted C. pilosa showed reduced productivity under the highest light intensity. In general, nitrate and amino acid levels decreased at higher light intensity, while sugar and organic acid concentrations increased. In C. pilosa osmolality tended to rise with increasing light intensity, while in the other species it tended to fall. Under low light intensity, the drop in soluble carbohydrate contents is osmotically compensated for by an enhanced nitrate concentration. It is concluded that competition between nitrate and reduction for reductants and ATP from photosynthesis may have important ecological consequences for the adaptation of plants to low or high light conditions. Additionally, the patterns of ionic changes due to increased light intensities were essentially the same in all selected species, indicating similar characteristics of heir mineral ion and organic acid metabolism as well as in field-grown Carex species.

Influence of light regimes on phyllosomal growth and timing of moulting in Thenus orientalis (Lund) (Decapoda: Scyllaridae)

Newly hatched phyllosomas of Thenus orientalis (Lund) were successfully reared under conditions of natural light (D/L), continuous dark (24D) or continuous light (24L). Survival, duration of intermoult periods, moult increment in total body length, and timing of moulting through larval stages were monitored. Survival and growth under 24L was lower than that under D/L and 24D; this may be a result of decreased phyllosomal feeding activity under 24L, caused by a photopositive reaction drawing the phyllosomas away from food at the bottom. There were no differences in phyllosomal development under D/L and 24D. When phyllosomas were reared under D/L, moulting was synchronized and occurred around dawn. Moulting of those reared under 24D or 24L was not synchronized and occurred irregularly. These results indicate that, in phyllosomas, light regime influences the endogenous rhythmic function responsible for the regulation of moulting time. When phyllosomas reared under D/L metamorphosed to the nisto stage, synchronized moulting switched from dawn to after dusk. Furthermore, nistos and juveniles moulted only nocturnally, with apparent synchronicity. This suggests that the switch from planktonic to benthic lifestyle, with consequent different predation pressures, necessitates a change in the timing of moulting.

Leaf structural characteristics of 31 hardwood and conifer tree species in central Wisconsin: Influence of light regime and shade-tolerance rank

Leaf structural characteristics were examined in understory and open-growing individuals of 26 hardwood and five conifer tree species, representing a range of shade-tolerance classes, in central Wisconsin. Sun leaves of open-growing hardwoods generally had greater thickness, specific mass and stomatal density than shaded leaves in the understory. In contrast, the conifer species exhibited few consistent differences in sun-shade needle length and specific leaf mass. Guard-cell length was not consistently different between sun and shade leaves of the hardwood species. Oaks had greater leaf thickness and stomatal density but lower guard-cell lengths compared to other hardwoo. Shade-intolerant hardwood species generally had greater sun- and shade-leaf thickness, specific leaf mass and guard-cell length than more-tolerant species. These differences in hardwood leaves suggest that acclimation to light regime exists for species representing a broad range of tolerances, and that differences in sun-shade leaf structure among species may vary with shade tolerance.

Pathway of dark inorganic carbon fixation in two species of diatoms: influence of light regime and regulator factors on diel variations

Pathway of dark inorganic carbon fixation in two species of diatoms: influence of light regime and regulator factors on diel variations

Influence of Light Regime and Leaf Nitrogen Concentration on 77k Fluorescence in Leaves of Four Tropical Grasses: No Evidence for Photoinhibition

This work was undertaken to determine if the stimulation of growth associated with shading of some tropical C4 grasses growing on soils with low to moderate nitrogen availability is partly due to overcoming photoinhibition (i. e. damage caused by excessive light). Four grasses (green panic, carpet grass, buffalo grass and kikuyu) were grown in full sunlight and at 37% of full sunlight, and given a low or high nitrogen supply. Despite differences of up to twofold in leaf nitrogen and chlorophyll concentration between high and low nitrogen treatments in all four grasses, photoinhibition measured by reduction in chlorophyll fluorescence was less than 3% in leaves of low nitrogen content that developed in full sunlight. Therefore, photoinhibition is not a contributor to the poor growth of nitrogen-limited grasses in full sunlight. A second objective was to determine if low nitrogen content predisposed shade-grown leaves to photoinhibition when they were subsequently exposed to full sunlight. Green panic plants that had been given either high or low nitrogen supply and grown in 37% of full sunlight were transferred to full sunlight and the extent of photoinhibition was followed over 8 days. The amount of photoinhibition that occurred was small (&lt;6%) compared with plants grown at either nitrogen level in full sunlight. Therefore, shade and low nitrogen content separately or in combination did not cause any appreciable photoinhibition in green panic.

Influence of Light Regime and Nitrate Fertilization on Nitrate Reductase Activity and Concentrations of Nitrate and Arginine in Tissues of Three Cultivars of Grapevines

Three grapevine (<i>Vitis vinifera</i> L.) cultivars, Chardonnay, Malbec, and Zinfandel were grown in sand culture at four different levels of solar radiation (100%, 50%, 28%, and 8% of full sunlight) in combination with three different levels of nitrogen (16, 4, and 1 mM nitrate). Nitrate in petioles and blades was inversely related to light availability and directly related to nitrogen level. Dry matter per unit length of shoot growth, total cane dry wt./vine and nitrate reductase (NR, the enzyme that catalyzes the reduction of NO₃ to NO₂) activity of leaf blades were related directly to light intensity, decreasing sharply under reduced solar radiation. The influence of solar radiation on the level of arginine was variable. The concentration of arginine in dormant cane tissues depended mainly on cultivar and on the concentration of nitrogen in the nutrient solution. Nitrate reductase activity was related inversely to petiole nitrate concentration and correlated highly with weight per centimenter of cane. The level of nitrate accumulated in petioles and leaf blades was modulated, at least in part, by the activity of nitrate reductase. It is concluded that where climate is variable, especially during the bloom sampling period, petiole nitrate may not reflect the true nitrogen status of vineyards.

Blood Glucose Levels in Young Chickens: The Influence of Light Regimes

Young male broiler-cross chickens, five to eight weeks of age were subjected to the following conditions: (1) ad libitum fed and exposed to a 12 hr. light—12 hr. dark lighting regime approximating the normal day light time of the outside environment; (2) fasted 12–31 hrs. and exposed to the same lighting regime as in (1); (3) ad libitum fed and exposed to continuous light or darkness; and (4) ad libitum fed and exposed to a lighting regime of 12 hrs. light and 12 hrs. dark, however, the initiation of the light period was 8 hrs. out of phase with the lighting regime employed in (1). Blood samples were drawn at various times and blood glucose levels determined for each sampling period.The data indicated a normal rhythmic pattern of blood glucose level (elevated during the period of illumination) in ad libitum fed, normally lighted birds and a reduced rhythmic pattern superimposed on the gradually declining blood level in the fasted birds exposed to the same lighting regime. Birds exposed to continuous light showed no rhythmic pattern. Exposure to continuous darkness resulted in an altered rhythm with an elevated period of possibly shorter duration than birds on a normal light regime (1). Birds on an out-of-phase lighting regime exhibited a response to the initiation of illumination similar to the birds in (1). However, these appeared to be a secondary influence of some other controlling factors as there was variation in the data collected indicating a non-uniform response of the birds tested.The conclusion that was drawn was that in other experiments where blood glucose level is used as a physiological indicator appropriate consideration must be given to conditions of feeding, lighting, and sampling time when designing experiments.

Influence of Light Regime on the Toxicity and Physiological Activity of Herbicides

The responlse of plants to certain herbicides is inifltieniced by the light coniditions precedinig or followinig applicatioln of the herbicide (14, 15, 16. 18, 21t) but the physiological basis for the differential activity of certaini herbicidal compounds in relation to the light conditions tunider which they are applied is uincertaini in most cases. This paper deals witlh 2 sutch lighlt-infltuence(d responises of plants to herbicides. Onle series of experimiients was perforn,ed to study an observation first reported by Salisbury (21) that plants treated with 2 4-dinitrophenol (DNP) are considerably more injured when the plants receive darkness after treatment than when they are exposed to light following application of the compound. Another series of investigations deals with the physiological activity of sodiumii 2, 4-dichlorophenoxyacetic acid (2, 4-D) in pllants as iniflueenced by uiltraviolet light anid the light regime to which plants are subjected after UVirra(liation and auxin treatmenit. There are many reports in the literature concerninig the effects of DNP on photosynthesis and photophosphorylationl (2, 17, 26), respiration anid oxi(lative phosphorylatiol (i 5 7), and other energyrequiring processes involvingo hi-h eniergy phosphate comlpounds (1, 19). In such stutdies the toxicity of DNP anid related col)ipounids is often marked!y infltueniced by the pH at which the material is applied to plants (23), an(d the carrier in which the material is applied (8). Salisbury (21) has suggested that the physiological basis for the differential toxicity of DNP to plants suibjected to light or dlarkness after DNP treatment may lie in a difference in senisitivity of the oxi(lattive and photosynithetic phosphorylationi mechaniismiis to DNP. Sinice DNP is more phytotoxic wheni its application is followed by (larkiess, D)NP mlay be inhibiting oxi(lative phosphory!ation but lnot photoplosphorytatioll. T hus, the level of ATP in plaints left in the (lark after DNP treatment wvould be lowered anid result in observable plant damage, but plants treated anid left in the light might avoid injury. Ohmura (17) and Wessels (26) have inideed demiionstrate(d a pathway of photoIhosphorylation whiclh is inisenisitive to DNP at concenitrations which inhibit oxi(lative phosphorylationi. De Zeeuw and Leopold (10) have reported that tomato plants irradiated with UV light for short periods of time do not exhibit the normal epinastic responses following auxini (iiapthalene acetic acid) treatment. IJltraviolet radiationi given before auxini treatment was more effective in preventinig epinasty in atuxin-treated plants than UV radiation given after auxini treatmiient. In other experimiients they (letermiined that UV ra(liation did not significantly affect the uptake of auxini. They concluded that the prevention of auxin responises in UV irradiate(l plants was due to a preventioni of auxin actioni insi(le the plants. It has beeni noted freqtuently that the physiological anid histological effects of UV on plant anid animal tissues can be overcomiie or reversed by wlhite light. For example, the inhibitory effects of UN' light oni such videly diverse processes as chlorophyll destruction (25), inactivation of bacteriophages (11), and growth of fuingi (12) can be reversedl by white light followving UV radiation. The mechanism of this photoreversal is still obscure, and experimental restults are diffictult to interpret (ltle to the multiplicity of physiological processes in plants affecte(d 1w UNV radiation. The present work was conducted to elaborate uponl these light-infltuenced responises of pllants to 2. 4-D, DNP, anid related comiipotunids alld shed(l ne light oln the plhysiological basis for the phytotoxicity of these compounds.