Variation In Photosynthetic Characteristics Research Articles

Variation in photosynthetic characteristics with growth form in a water-limited scenario: Implications for assimilation rates and water use efficiency in crops

Photosynthesis is a complex process that is intrinsically determined by two main components: the CO2 diffusion from the atmosphere to the chloroplast and the biochemistry. Among CO2 diffusion, mesophyll conductance within the leaf (gm) has been receiving attention in the recent years as a key player determining photosynthesis both across species and in response to the environment; furthermore, gm estimation allows for disentangling the complete set of photosynthesis underlying mechanisms. In a water-limited scenario where crop productivity and efficiency need to be increased, the analysis of available data from photosynthesis among vascular plants and its response to water stress results helpful for a better understanding of crop management and improvement. Here, photosynthesis data are compiled to elucidate if crop and wild species from different growth forms present different photosynthesis limitations under optimum and water stress conditions. From the available data, a double process of apparent photosynthesis selection is revealed: higher values from ferns to woody and herbaceous species and, among angiosperms, a tendency towards greater photosynthesis in crop species (although constrained by growth form). The causes of such photosynthesis variation are discussed. Moreover, crop and herbaceous species present a shift in photosynthesis limitations towards lower mesophyll diffusion constraints, under both well-watered and water-stress conditions. These particular photosynthesis characteristics in crops present several implications for the possible improvement of CO2 assimilation and water use efficiency, providing new guidelines for future engineering and management in agriculture.

Variation of photosynthetic characteristics and yield in wild and cultivated species of yams (Dioscorea spp.) from Koraput, India

Variations in leaf gas-exchange characteristics, PSII activity, leaf pigments, and tuber yield were investigated in seven wild and one cultivated species of Dioscorea from Koraput, India, in order to find out their overall adaptability to the environment. The leaf photosynthetic rate, transpiration, stomatal conductance, water-use efficiency, carboxylation efficiency, and photosynthetic pigments were significantly higher in some wild species compared to the cultivated species. In addition, some wild species showed better photochemical efficiency of PSII, photochemical quenching, and electron transport rate in comparison to cultivated one. Furthermore, leaf dry matter accumulation and tuber yield was also higher in some wild species compared to the cultivated species. Taken together, the wild species, such as D. oppositifolia, D. hamiltonii, and D. pubera, showed the superior photosynthetic efficiency compared to the cultivated D. alata and they could be used for future crop improvement programs.

Diurnal and seasonal variations in photosynthetic characteristics of switchgrass in semiarid region on the Loess Plateau of China

In order to use rationally switchgrass (Panicum virgatum L.) introduced in a large scale in semiarid regions on the Loess Plateau of China, we investigated and compared soil water storage dynamics, diurnal and seasonal changes in leaf photosynthetic characteristics, and biomass production of switchgrass grown under three different row spacing (20, 40, and 60 cm). Results indicated that photosynthetic parameters showed a pronounced seasonality. Diurnal course of net photosynthetic rate (PN) was bimodal, showing obvious midday depression, which was mainly due to stomatal limitation in May and June, by nonstomatal limitation in August, and both stomatal and nonstomatal factors in September. Generally, PN, stomatal conductance, instantaneous water-use efficiency, light-saturated net photosynthetic rate, saturation irradiance, and compensation irradiance increased with increasing row spacing. Plant height, leaf width, and a relative growth rate of biomass accumulation were significantly higher at the row spacing of 60 cm, while 20 cm spacing showed significantly higher aboveground biomass production and the biomass water-use efficiency. All these confirmed that soil water is the key limiting factor influencing switchgrass photosynthesis, and suggested that the wide row plantation (i.e., 60 cm) was more beneficial to switchgrass growth, while narrow spacing was in favor of improving switchgrass productivity and water-use efficiency.

Variations in photosynthetic characteristics and yield of maize in potato/maize intercropping systems

Intercropping of potato with maize has been a traditional cropping system widely practiced in the mountain regions of Southwest China.Although changes have occurred in light environment of maize due to intercropping,few reports have been analyzed the importance of competition for light and related effects on maize yield in potato/maize associations.A potato/maize intercropping field experiment with two different potato-maize row ratios was carried out to determine the dynamic changes in maize features.The features analyzed included leaf area index(LAI),special leaf weight(SLW),chlorophyll a(Chla),chlorophyll b(Chlb),total chlorophyll(Chla+Chlb) and chlorophyll a/b ratio(Chla/b) of maize at different growth stages.Also photosynthetic active radiation(PAR) and gas exchange parameters of upper and lower leaves at tasseling stage of mazie were analyzed along with yield using mono-cropped maize as the control.The respective potato-to-maize row number ratios used in the study were 2:2 and 3:2.The results showed a substantial drop in maize LAI at all growth stages while SLW only dropped at the early growth stages before milking under intercropping compared with monocropping.Chla,Chlb and Chla+Chlb also markedly decreased in the 3:2 intercropping system at all growth stages while it only decreased in the 2:2 intercropping system at seedling,jointing and silking stages.Chla/b ratio dropped at jointing stage,was subsequently enhanced at silking stage and showed no significant difference at seedling and milk stages.Compared with the 2︰ 2 intercropping system,the 3:2 intercropping system had significantly lower LAI at all the growth stages except the seedling stage.Also noted were high Chla,Chlb and Chla+Chlb at all the growth stages except the milking stage,and high Chla/b ratio at silking and milking stages.SLW was not significantly different at all growth stages between 2:2 and 3:2 intercropping systems.Furthermore,PAR,net photosynthesis rate(Pn),stomatal conductance(Gs),transpiration rate(Tr) and water use efficiency(WUE) declined in all treatments from upper to lower leaves of maize.Significantly lower Pn,Gs,Tr and high Ci were noted in lower leaves of maize under intercropped conditions than under mono-cropped conditions.No significant changes were noted between intercropped and mono-cropped treatments in terms of Pn,Gs,Tr and Ci of maize upper leaves.PAR in both upper and lower leaves was markedly higher in intercropping than in mono-cropping whereas no marked variations were noted in WUE of the leaves.In comparison with the 2:2 intercropping system,the 3:2 system showed substantially lower PAR,Gs and Tr in both upper and lower leaves,similar Pn in upper leaves and lower Pn in lower leaves.The variations in Pn,Gs and Ci suggested that intercropping limited photosynthetic activity in lower leaves of maize due to non-stomatal processes in the 2:2 intercropping system.However,it enhanced these parameters in the 3:2 intercropping system due to active stomatal processes.In conclusion,intercropping substantially decreased maize yield at harvest due to changes in photosynthetic characteristics in potato/maize systems.Nonetheless,the land equivalent ratios were 0.88 and 1.24 in the 2:2 and 3:2 intercropping systems,respectively.This suggested that there was no advantage in the 2:2 intercropping system but there existed obvious advantages in the 3:2 intercropping systems.

Seasonal variability of photosynthetic characteristics influences growth of eight tropical tree species at two sites with contrasting precipitation in Panama

Relative to closed-canopy tropical forests, tree seedlings planted in open grown areas are exposed to higher light intensity, air temperatures, vapor pressure deficit, and greater seasonal fluxes of plant available water than mature tropical forests. The species-specific adaptive capacity to respond to variable precipitation and seasonality in open grown conditions, therefore, is likely to affect species performance in large-scale reforestation efforts. In the present study, we compared the photosynthetic characteristics of eight tropical tree species within and between seasons at two study sites with contrasting dry season intensities. All species except Pseudosamanea guachapele reduced leaf physiological function between the wet and dry seasons. The contrasting severity of seasonal drought stress at the study sites constrained growth rates and photosynthetic characteristics differently. Variation of photosynthetic characteristics at the species level was high, particularly in the dry season. Faster growing species at the less seasonal site, Terminalia amazonia, Inga punctata, Colubrina glandulosa, and Acacia mangium, exhibited a greater adaptive capacity than the other species to down-regulate leaf photosynthesis between seasons. As the dry season was more severe at the more seasonal site, most species strongly reduced physiological function regardless of relative growth rates, except two species ( Tectona grandis and P. guachapele) with widespread distributions and relatively high drought tolerance. Our results underscore the need to consider seasonal drought tolerance when selecting tree species for specific reforestation sites.

Diurnal light curves and landscape-scale variation in photosynthetic characteristics of Thalassia testudinum in Florida Bay

When using pulse-amplitude modulated (PAM) fluorometry to measure landscape-scale photosynthetic characteristics, diurnal variations in fluorescence during sampling may confound the assessment of the physiological condition. In this study, two photophysiological assessment techniques: Diurnal Yield and Diurnal Rapid Light Curve (RLC) were investigated in an attempt to incorporate the temporal and spatial scales of sampling into a physiological assessment of Thalassia testudinum in Florida Bay. Photosynthesis–irradiance (P–E) curves were calculated using both methods and the ability of each to predict the relationship between relative electron transport rates and irradiance was assessed. Both methods had limitations in providing consistent estimates of photosynthetic efficiency or capacity. The Diurnal Yield method produced unrealistically high predictions of photosynthetic capacity (relative electron transport rate (rETR max), 417–1715) and saturation irradiance ( I k, 1045–4681 μmol photons m −2 s −1). In contrast, the Diurnal RLC method generally produced predictions of rETR max (100–200) and I k (300–500 μmol photons m −2 s −1) which were similar to average values calculated from each day's RLCs. The Diurnal RLC method was unable to predict photosynthetic efficiency ( α) only when ambient irradiances were continuously > I k during the sampling period. We believe that with sampling modifications in high-light or shallow environments, such as starting sampling earlier in the morning, extending sampling later in the day, or using the average α from each day's RLCs, that the Diurnal RLC method can produce representative estimates of rETR max, α, and I k, providing a method to characterize seagrass photosynthesis at the landscape-level. The Diurnal RLC method does not negate Diurnal variation but it produces a curve that incorporates the changing ambient light environment into the assessment of seagrass physiological status.

Genetic variation in photosynthetic characteristics among invasive and native populations of reed canarygrass (Phalaris arundinacea)

With the extensive spread of invasive species throughout North America and Europe there is an urgent need to better understand the morphological and physiological characteristics of successful invasive plants and the evolutionary mechanisms that allow introduced species to become invasive. Most ecological studies have focused on morphological differences and changes in community dynamics, and physiological studies have typically explored the differences between native and invasive species. In this study, 15 different genotypes of Phalaris arundinacea from both its native (European) and invasive (North American) range were grown in a common garden experiment to monitor the physiological differences between native and invasive genotypes. Here we present data that suggests high variability exists in the physiological traits among genotypes of P. arundinacea, yet genotypes from the native range are not necessarily physiologically inferior to the hybridized invasive genotypes. Previous work has shown that multiple introductions of P. arundinacea from various European locations to the United States resulted in numerous hybridization events, yielding more genetic variability and phenotypic plasticity in the invasive range. Of the genotypes studied, both morphological and physiological traits of genotypes with French origin were significantly different from the plants from the Czech Republic, North Carolina, and Vermont. The lack of clear differences between native and invasive genotypes indicates that physiological traits may be highly conserved in P. arundinacea and enhanced photosynthetic rates are not indicative of successful invasive genotypes. Instead, morphological traits and defensive secondary compound metabolism may play a more important role in the success of P. arundinacea within its invasive range, and patterns of genetic variation in physiological traits between invasive and native range may be more important than the mean traits of each region when explaining reed canarygrass’ invasive potential in North America.

Photosynthetic Performances of Transplanted Cypripedium flavum Plants

To explore the conservation and cultivation of Cypripedium flavum at comparatively lower altitudes, a study on variations in photosynthetic characteristics was conducted on C flavum plants from the high mountains of the eastern Himalayas. Plants of same size (6 leaves, 35-40 cm height) were selected from Tianshengqiao (alt. 3,450 m) and planted at the gardens at Zhongdian (alt. 3,200 m) and Kunming (alt. 1,900 m). The leaves of C flavum at Tianshengqiao and Zhongdian exhibited higher photosynthetic rate, stomatal conductance, transpiration rate, apparent quantum yield, and carboxylation efficiency than their counterparts at Kunming. The optimal temperatures for photosynthesis of C. flavum plants growing at Tianshengqiao, Zhongdian, and Kunming were 18, 19 and 2 degrees C, respectively. The optimal temperature also increased with increasing photosynthetically active radiation (PAR). However, the photosynthetic responses of C. flavum to PAR were similar at the three sites. The photosynthesis reached light saturation at the PAR of 746-832 mu mol m(-2)s(-1). The inability of C. flavum to acclimate to higher temperature resulted in the depression of photosynthetic rate at the lower altitude (Kunming). The results suggest that C. flavum adapts poorly to the warmer temperatures at low altitudes. It can be cultivated at a lower attitude, but proper agronomical methodology will need to be developed for better growth.

Effects of elevated CO2 concentration on growth, annual ring structure and photosynthesis in Larix kaempferi seedlings

We evaluated the effects of elevated carbon dioxide concentration ([CO2]) and two nutrient regimes on stem growth rate, annual ring structure and temporal variations in photosynthetic characteristics of seedlings of Japanese larch (Larix kaempferi (Lamb.) Carr.). Seedlings were grown in phytotron chambers in an ambient (360 ppm) or an elevated (720 ppm) [CO2] in two nutrient regimes for one growing season. Elevated [CO2] reduced stem height and increased stem basal diameter compared with ambient [CO2]. The effect of elevated [CO2] on growth tended to be greater at high-nutrient supply than at low-nutrient supply. Elevated [CO2] had no significant effect on ring width or the number of tracheids per radial file. There was no obvious difference in cell wall thickness or the relative area of the cell wall between seedlings grown in ambient or elevated [CO2]. Although growth in elevated [CO2] resulted in a slight increase in cell diameter, the increase had a relatively minor effect on the relative area of the cell wall. Net assimilation rate increased in response to elevated [CO2]; however, the increase in whole-crown photosynthetic rate (Total Agrowth) in seedlings in the elevated [CO2] treatment was minimal because of the smaller specific needle area and acclimation of the photosynthetic characteristics of the needles to the growth [CO2]. In conclusion, we observed no obvious enhancement in the capacity for carbon fixation in Japanese larch seedlings grown in the presence of elevated [CO2] that might be attributable to changes in stem growth. However, elevated [CO2] caused changes in the temporal pattern of stem growth and in some anatomical features of the tracheids.

Variation in Photosynthetic Characteristics and Leaf Area Contributes to Spathiphyllum Cultivar Differences in Biomass Production

Three genetically related Spathiphyllum cultivars, Claudia, Double Take, and Petite with similar initial sizes and biomass, were grown in a shaded greenhouse and fertilized with a constant supply of nitrogen at 200 g m-3 using an ebb-and-flow fertigation system. Seven months later, Claudia and Double Take had plant sizes and biomasses significantly greater than Petite. Stomatal conductances of Claudia and Double Take were 30 % greater, thus net photosynthetic rates (PN) were significantly higher than in Petite. In addition, the leaf areas (LA) of Claudia and Double Take were 60 % larger than of Petite. Since PN was expressed per leaf surface area, the greater the LA was, the more CO2 was fixed. Thus, the differences in plant size and biomass production of Claudia and Double Take compared to Petite are attributed to high PN and increased LA.

Photosynthetic characteristics of Thalassia testudinum measured in situ by pulse-amplitude modulated (PAM) fluorometry: methodological and scale-based considerations

Shoot-to-landscape scale sources of variation in photosynthetic characteristics of Thalassia testudinum, as measured in situ using a submersible pulse-amplitude modulated fluorometer (diving-PAM), were investigated. Shoot-scale variation was assessed to develop a standard-methods protocol for this species. Significant within-shoot and among-shoot scale variation was observed for several PAM-fluorescence parameters. The fraction of incident photosynthetically active radiation (PAR) absorbed by rank 1 (youngest) leaves, 0.67±0.03, was significantly lower than the PAR absorbed by rank 2 and 3 leaves (0.78±0.04 and 0.77±0.04, respectively). Quantum yields ( Y) and photosynthetic efficiency ( F v/ F m) exhibited greater variability and generally decreased with increasing leaf age ( Y=0.78±0.02, 0.78±0.03, and 0.76±0.06 and F v/ F m=0.79±0.02, 0.77±0.5, and 0.75±0.06 for rank 1, 2, and 3 leaves, respectively). Maximum fluorescence of light-acclimated leaves ( F′ m) significantly decreased from the base to the tip of leaves (1032±203, 1059±139, and 793±107 for the base, middle and tip of the leaf) and Y was significantly reduced from 0.68–0.76 to 0.27–0.62 when measured where leaf lesions were present. However, paired comparisons (with versus without lesions at the tip of the leaf) for the base, middle, and tip areas of rank 2 leaves indicated that lesions effects on photosynthesis were localized only to the area of the lesion (tip). The Y exhibited relatively high variability for short-shoots within seagrass die-off patches and were significantly reduced for short-shoots exhibiting die-off symptoms (rotten leaf base grayish-green leaf color, but no lesions). Negative response slopes for Y and F v/ F m, measured as part of a landscape-scale sampling program, revealed the presence of significant diurnal (time-of-day) and photosynthetic photon flux density (PPFD) related variation, with a more negative slope for Y. These results indicate that the selection of leaf tissue, short-shoot location, and time of measurement need to be considered when determining photosynthetic rates for seagrasses in situ.

The Content of Light-Harvesting Complexes in Different Maize (Ze mays L.) Genotypes

Genetic analysis of the content of light-harvesting complexes of thylakoid membranes was accomplished for the first time during the study of intraspecific variation in photosynthetic characteristics. The existence of genetically determined differences between genotypes together with positive heterosis in F1 generation was demonstrated.

Variations in photosynthetic characteristics of the Antarctic marine brown algaAscoseira mirabilisin relation to thallus age and size

Growth, photosynthesis, dark respiration, chlorophyll a (Chl a) content and dry weight were measured in 2- and 3-year-old plants of Ascoseira mirabilis (Ascoseirales), cultivated in the laboratory under changing daylengths which matched the seasonal variations in the Antarctic. Determinations were made in four thallus regions. Growth of A. mirabilis was seasonal, with higher rates in spring. Parameters such as net photosynthesis (P max), photosynthetic efficiency (α), both measured on a fresh weight (FW) basis, and dry weight content, showed significant age- and size-dependent variations. In contrast, no variations were observed in dark respiration, initial light-saturating point of photosynthesis (I k) and Chl a contents. P max had maximum values close to 16·5 μmol O2 g-1 FW h-1 in 2-year-old plants, whereas in 3-year-old plants maximum values of 8 μmol O2 g-1 FW h-1 were determined. The α-values reached maximum rates of 1.4 and 0.6 μmol O2 g-1 FW h-1 (μmol photons m-2 s-1)-1 in 2- and 3-year-old plants,...

Photosynthetic performance in wild emmer wheat, Triticum dicoccoides: ecological and genetic predictability

In a twin study, we have shown that wild emmer wheat, Triticum dicoccoides, the progenitor of all cultivated wheats, harbours important genetic variation (Vg) in photosynthetic characteristics. This Vg resides within and between populations and ecogeographical regions in Israel, which is the center of origin and diversity of wild emmer wheat. Here we analyzed, by univariate and multivariate methods, the significant differentiation of variation in photosynthetic characteristics of 107 genotypes from 27 populations of wild emmer in Israel, distributed in three ecogeographical regions including central, xeric (northern cold and eastern warm) marginal, and mesic (western) marginal populations. The highest photosynthetic efficiency was displayed by populations of the xeric marginal region, but most variation for photosynthetic capacity occurs between accessions within ecogeographical regions and populations. Genotypes and populations of T. dicoccoides having high photosynthetic capacity can be identified by climatic factors and isozyme markers. The identification by genetic markers, if substantiated by testcrosses, can facilitate the maximization of conservation, in situ or ex situ, and utilization of these photosynthetic genetic resources for improvement of hexaploid wheat (T. aestivum).

Compensating Effects to Growth of Changes in Dry Matter Allocation in Response to Variation in Photosynthetic Characteristics Induced by Photoperiod, Light and Nitrogen

High N-nutrition, high light and long photoperiod increased photosynthetic capacity (Amax) per leaf area of Raphanus sativus × raphanistrum. The effect of Amax on growth was enhanced by an increased fraction of dry matter partitioned into the shoot, resulting in a larger canopy. Low N-nutrition, low light and a short photoperiod reversed these responses. At intermediate combinations, such as low light and long photoperiod or high light and short photoperiod, Amax and the actual net photosynthesis per leaf area (A) neither correlated with the carbon uptake rate of the canopy as a whole nor with whole plant growth. A compensatory effect to growth of changes in dry matter partitioning in response to variation in photosynthetic characteristics induced by light and N-nutrition is discussed in terms of two competitive feedbacks. For growth a long photoperiod compensated for low light or low N-nutrition. The results indicate that extrapolations from rates to gains are only valid under defined environmental conditions, especially when different photoperiods and effects on leaf ontogeny are involved.

Effects of weather during leaf development on photosynthetic characteristics of soybean leaves

Net photosynthetic rates and mesophyll conductances at 25 °C at light saturation and air levels of carbon dioxide and oxygen were measured on recently fully expanded leaflets of second trifoliolate leaves of soybeans (Glycine max cv. Kent). Plants were grown outdoors in pots at Beltsville, Maryland with 14 planting times from May through August, 1983. Air temperature and humidity, and photosynthetically active radiation (PAR) were measured for the expansion periods of the second trifoliolate leaves. Rates of net photosynthesis ranged from 24 to 33 μmol m(-2) s(-1), and mesophyll conductances from 0.24 to 0.35 cm s(-1) for the different planting dates. Mean 24-h air temperatures ranged from 20.6 to 29.0 °C, and mean daily PAR ranged from 29.4 to 58.4 mol m(-2) d(-1) for the leaf expansion periods. There was a positive relationship between photosynthetic characteristics and PAR during leaf expansion, and a negative relationship between photosynthetic characteristics and leaf expansion rates, with 96% of the variation in photosynthetic characteristics accounted for by these two variables. Leaf expansion rates were highly correlated with air temperature.