Light Spectrum Variably Affects the Acclimatization of Grafted Watermelon Seedlings While Maintaining Fruit Quality

In many countries of Europe and Eastern Asia, watermelon production is mainly based on the use of grafted seedlings. Upon grafting, seedlings undergo a period of healing where artificial lighting is provided by light-emitting diodes in controlled chambers in order to accelerate and improve the healing process. The objective of our study was to test the effect of light quality on the final product (i.e., seedlings ready for transplanting) in the nursery, as well as to evaluate the possible implications on fruit quality after field cultivation. Narrow-band blue (B) and red (R) wavelengths, 64–36% R-B (36B), 76–24% R-B (24B), 88–12% R-B (12B), and 83–12% R-B plus 5% far-red (12B+FR) wavelengths were tested. 12B+FR enhanced the root dry weight, root architecture, and maximum photosynthetic rate, while RB combinations generally showed better root system development with increased blue portion. R light induced inferior root dry weight and quality indices (root/shoot and shoot–dry–weight/length ratios), lower gas exchange parameters, and chlorophyll content, but high shoot length and leaf area. B light led to inferior root architecture, lower stem diameter, leaf area, and maximum photosynthetic rate. Both R and B wavelengths showed decreased concentration of macronutrients and trace elements. After field cultivation, fruit quality (i.e., morphology and color), and valuable nutritive characteristics (i.e., phenolics, carotenoids, lycopene, antioxidants) maintained high quality irrespective of light treatments. Overall, 12B+FR performed well in almost all qualitative parameters including the morphology, the root development, and photosynthesis, while also maintaining high fruit quality.

Verification of our empirical understanding of the physiology and ecology of two contrasting plantation species using a trait database

The effects of climate change on forest ecosystems take on increasing importance more than ever. Information on plant traits is a powerful predictor of ecosystem dynamics and functioning. We reviewed the major ecological traits, such as foliar gas exchange and nutrients, xylem morphology and drought tolerance, of Cryptomeria japonica and Chamaecyparis obtusa, which are major timber species in East Asia, especially in Japan, by using a recently developed functional trait database for both species (SugiHinokiDB). Empirically, C. obtusa has been planted under drier conditions, whereas C. japonica, which grows faster but thought to be less drought tolerant, has been planted under wetter conditions. Our analysis generally support the empirical knowledge: The maximum photosynthetic rate, stomatal conductance, foliar nutrient content and soil-to-foliage hydraulic conductance were higher in C. japonica than in C. obtusa. In contrast, the foliar turgor loss point and xylem pressure corresponding to 50% conductivity, which indicate drought tolerance, were lower in C. obtusa and are consistent with the drier habitat of C. obtusa. Ontogenetic shifts were also observed; as the age and height of the trees increased, foliar nutrient concentrations, foliar minimum midday water potential and specific leaf area decreased in C. japonica, suggesting that nutrient and water limitation occurs with the growth. In C. obtusa, the ontogenetic shits of these foliar traits were less pronounced. Among the Cupressaceae worldwide, the drought tolerance of C. obtusa, as well as C. japonica, was not as high. This may be related to the fact that the Japanese archipelago has historically not been subjected to strong dryness. The maximum photosynthetic rate showed intermediate values within the family, indicating that C. japonica and C. obtusa exhibit relatively high growth rates in the Cupressaceae family, and this is thought to be the reason why they have been selected as economically suitable timber species in Japanese forestry. This study clearly demonstrated that the plant trait database provides us a promising opportunity to verify out empirical knowledge of plantation management and helps us to understand effect of climate change on plantation forests by using trait-based modelling.

Trait Response to Nitrogen and Salinity in Rhizophora mangle Propagules and Variation by Maternal Family and Population of Origin

Many coastal foundation plant species thrive across a range of environmental conditions, often displaying dramatic phenotypic variation in response to environmental variation. We characterized the response of propagules from six populations of the foundation species Rhizophora mangle L. to full factorial combinations of two levels of salinity (15 ppt and 45 ppt) reflecting the range of salinity measured in the field populations, and two levels of nitrogen (N; no addition and amended at approximately 3 mg N per pot each week) equivalent to comparing ambient N to a rate of addition of 75 kg per hectare per year. The response to increasing salinity included significant changes, i.e., phenotypic plasticity, in succulence and root to shoot biomass allocation. Propagules also showed plasticity in maximum photosynthetic rate and root to shoot allocation in response to N amendment, but the responses depended on the level of salinity and varied by population of origin. In addition, propagules from different populations and maternal families within populations differed in survival and all traits measured except photosynthesis. Variation in phenotypes, phenotypic plasticity and propagule survival within and among R. mangle populations may contribute to adaptation to a complex mosaic of environmental conditions and response to climate change.

Response to nitrogen and salinity in Rhizophora mangle propagules varies by maternal family and population of origin

Many coastal foundation plant species thrive across a range of environmental conditions, often displaying dramatic phenotypic variation in response to environmental variation. We characterized the response of propagules from six populations of the foundation species Rhizophora mangle L. to full factorial combinations of two levels of salt (15 ppt and 45 ppt) reflecting the range of salinity measured in the field populations, and two levels of nitrogen (N; no addition and amended at approximately 3 mg N per pot each week) equivalent to comparing ambient N to a rate of addition of 75 kg per hectare per year. The response to increasing salt included significant plasticity in succulence. Propagules also showed plasticity in maximum photosynthetic rate in response to N amendment, but the responses depended on the level of salt and varied by population of origin. Generally, survival was lower in high salt and high N, but the impact varied among populations. Overall, this study revealed significant phenotypic plasticity in response to salt and N level. Propagules from different populations differed in all traits measured. Variation in phenotypic plasticity and propagule survival in R. mangle may contribute to adaptation to a complex mosaic of environmental conditions and response to climate change.

Verification of our empirical understanding of the physiology and ecology of two contrasting plantation species using a trait database

The effects of climate change on forest ecosystems take on increasing importance more than ever. Information on plant traits is a powerful predictor of ecosystem dynamics and functioning. We reviewed the major ecological traits, such as foliar gas exchange and nutrients, xylem morphology and drought tolerance, of Cryptomeria japonica and Chamaecyparis obtusa , which are major timber species in East Asia, especially in Japan, by using a recently developed functional trait database for both species (SugiHinokiDB). Empirically, C. obtusa has been planted under drier conditions, whereas C. japonica has been planted under wetter conditions. Our analyses revealed followings: The maximum photosynthetic rate, stomatal conductance, foliar nutrient content and soil-to-foliage hydraulic conductance were higher in C. japonica than in C. obtusa and were consistent with the higher growth rate of C. japonica. In contrast, the foliar turgor loss point and xylem pressure corresponding to 50% conductivity, which indicate drought tolerance, were lower in C. obtusa than in C. japonica and are consistent with the drier habitat of C. obtusa. Ontogenetic shifts were also observed; as the age and height of the trees increased, many foliar nutrient concentrations decreased, and the foliar minimum midday water potential and specific leaf area also decreased. This suggests that an ontogenetic reduction in photosynthesis occurred due to an increase in drought stress with tree height and age. However, among the Cupressaceae worldwide, the drought tolerance of C. japonica and C. obtusa is not as high. This may be related to the fact that the Japanese archipelago has historically not been subjected to strong dryness. The maximum photosynthetic rate showed intermediate values within the family, indicating that C. japonica and C. obtusa exhibit relatively high growth rates in the Cupressaceae family, and this is thought to be the reason why they have been selected as economically suitable timber species in Japanese forestry. This study clearly demonstrated that the plant trait database provides us a promising opportunity to verify out empirical knowledge of plantation management and helps us to understand effect of climate change on plantation forests by using trait-based modelling.

Photosynthetic Light Response of Floricane Leaves of Erect Blackberry Cultivars from Fruit Development into the Postharvest Period

The photosynthetic light response of commercial blackberry cultivars (Rubus L. subgenus Rubus Watson) is largely unexplored, although they are frequently grown in full sun. In this experiment, light response curves of floricane leaves from the cultivars Natchez, Apache, Navaho, and Von were examined throughout the following production stages: before shiny black fruit were present (before harvest, BH), during peak production of fruit (peak harvest, PH), and when most fruit had fallen from plants or any remaining were dull black (after harvest, AH). Each cultivar was evaluated between an irradiance of 2000 and 0 μmol·m–2·s–1. The estimated maximum photosynthetic rate (photosynthetic capacity, PNmax) was greater BH than AH across all cultivars, whereas ‘Natchez’ had a greater PNmax BH and PH compared with the other cultivars. During AH, all cultivars had a similar PNmax. The BH response curves declined under the highest irradiance measured, whereas the PH and AH response curves remained stable at similarly high irradiance. Of the four cultivars, Apache, Navaho, and Von appeared to be more photosynthetically limited than Natchez under increasing irradiance. Based on the cultivar-specific performance observed, blackberry response to light is a relevant trait that breeding programs should consider for improving cultivar adaptability to local and regional conditions.

Seasonal coordination of leaf hydraulics and gas exchange in a wintergreen fern

Wintergreen fern Polystichum acrostichoides has fronds that are photosynthetically active year-round, despite diurnal and seasonal changes in soil moisture, air temperature and light availability. This species can fix much of its annual carbon during periods when the deciduous canopy is open. Yet, remaining photosynthetically active year-round requires the maintenance of photosynthetic and hydraulic systems that are vulnerable to freeze–thaw cycles. We aimed to determine the anatomical and physiological strategies P. acrostichoides uses to maintain positive carbon gain, and the coordination between the hydraulic and photosynthetic systems. We found that the first night below 0 °C led to 25 % loss of conductivity (PLC) in stipes, suggesting that winter-induced embolism occurred. Maximum photosynthetic rate and chlorophyll fluorescence declined during winter but recovered by spring, despite PLC remaining high; the remaining hydraulic capacity was sufficient to supply the leaves with water. The onset of colder temperatures coincided with the development of a necrotic hinge zone at the stipe base, allowing fronds to overwinter lying prostrate and maintain a favourable leaf temperature. Our conductivity data show that the hinge zone did not affect leaf hydraulics because of the flexibility of the vasculature. Collectively, these strategies help P. acrostichoides to survive in northeastern forests.

Effects of leaf age, elevation and light conditions on photosynthesis and leaf traits in saplings of two evergreen conifers, Abies veitchii and A. mariesii

Aims Subalpine coniferous species are distributed over a wide range of elevations in which they must contend with stressful conditions, such as high elevations and extended periods of darkness. Two evergreen coniferous species, Abies veitchii and Abies mariesii, dominate at low and high elevations, respectively, in the subalpine zone, central Japan. The aim of this study is to examine the effects of leaf age, elevation and light conditions on photosynthetic rates through changes in morphological and physiological leaf traits in the two species. Methods We here examined effects of leaf age, elevation and light conditions on photosynthesis, and leaf traits in A. veitchii and A. mariesii. Saplings of the two conifers were sampled in the understory and canopy gaps at their lower (1600 m) and upper (2300 m) distribution limits. Important Findings The two species showed similar responses to leaf age and different responses to elevation and light conditions in photosynthesis and leaf traits. The maximum photosynthetic rate of A. veitchii is correlated negatively with leaf mass per area (LMA) and non-structural carbohydrate (NSC) concentration. LMA increased at high elevations in the two species, whereas NSC concentrations increased only in A. veitchii. Therefore, the maximum photosynthetic rate of A. veitchii decreased at high elevations. Furthermore, maximum photosynthetic rates correlate positively with nitrogen concentration in both species. In the understory, leaf nitrogen concentrations decreased and increased in A. veitchii and A. mariesii, respectively. LMA decreased and the chlorophyll-to-nitrogen ratio increased in understory conditions only for A. mariesii, suggesting it has a higher light-capture efficiency in dark conditions than does A. veitchii. This study concluded that A. mariesii has more shade-tolerant photosynthetic and leaf traits and its photosynthetic rate is less affected by elevation compared with A. veitchii, allowing A. mariesii to survive in the understory and to dominate at high elevations.

Photosynthetic Characterization and Response to Drought and Temperature in Wild Asparagus (Asparagus acutifolius L.)

The wild asparagus species Asparagus acutifolius L. is widespread in Mediterranean and subtropical environments, where its spears are consumed regularly. The species is known to have ecophysiologic plasticity, however there is no literature on this subject. This work aimed at assessing the photosynthetic characteristics of this wild species of asparagus, grown under full light (FL) and partial (i.e., about 40%) light (PL) conditions, and evaluating its ecophysiologic response to drought and temperature stress. The photosynthetic response to light of spears and of new cladodes (NC; current year) and old cladodes (OC; previous year) was measured using an infrared gas analyzer coupled with a climatized cuvette chamber. Cladodes net photosynthesis at high irradiance was also measured at varying air temperatures and decreasing soil water availability. Results indicate that developing spears were photosynthetically active with no difference between FL and PL treatments. Photosynthetic rates did not differ between NCs and OCs and were greater for FL cladodes, except at low irradiance. Well-watered plants were photosynthetically active from 0 to 45 °C, with a maximum photosynthetic rate of up to 9 µmol·m–2·s–1 at 30 °C and a decrease of about 60% at 45 °C. The species also demonstrated high tolerance to drought, with positive net photosynthesis even at predawn leaf water potential values of –2.4 MPa. Showing great ecophysiologic plasticity, this wild asparagus could be an interesting species in areas were conventional crop species are not profitable economically, or as an intercrop in agroforestry systems.

Effect of Azorhizobium caulinodans on yield in plant growth regulator induced nodulated wheat

In the laboratory seedling were induced with nodule-like outgrowths using different growth regulators 2,4-D,IBA and NAA in nitrogen free Hoagland solution. Induced seedlings were inoculated with Azorhizobium caulinodans (ORS 571) in wheat variety C-306. One set was also raised as control. The treated paranoulated wheat seedlings were transferred to pot culture. The data was collected on 30, 60 and 90 days after sowing, which reveals that as a Azorhizobium caulinodans with 2,4-D treated plants shows maximum photosynthetic rate followed by NAA and IBA combinations. The biomass production was maximum in Azorhizobium caulinodans treated with 2,4-D followed by IBA and NAA.