Seedlings of the three coniferous species including Thujopsis dolabrata var. hondai Makino were raised under weak shade in a nursery in order to examine the photochemical and nonphotochemical dissipations of excited energy at PSII. The dry matter growth 20 weeks after germination was smallest in T. dolabrata var. hondai. This was due to the low photosynthetic capacity in addition to the small leaf weight ratio of the seedlings and the large leaf specific weight. The specific ranking of rETRmax (the maximum relative electron transport rate) was different from that of NPQmax (the maximum of non-photochemical quenching) ; T. dolabrata var. hondai was characterized by the high NPQmax relative to the low rETRmax. A slight depression in Fv/Fm, (light stress parameter) was recognized only for Cryptomeria japonica in the cotyledon period. A large depression in Fv/Fm was observed for C. japonica and T. dolabrata var. hondai in the post-cotyledon period. These depressions in Fv/Fm seemed to be closely associated with the low levels of rETRmax but may have also been related to the effects of NPQmax and foliage morphology and architecture. The light responsibility of T. dolabrata var. hondai seedlings differed greatly from that of Pinus densiflora Sieb. et Zucc. and differed significantly from that of C. japonica.
The non-destructive estimation of internal quality of fruits for on-line grading to achieve higher product consistency and enhanced safety will greatly benefit the consumer and the fruit industry as a whole. This research was aimed at developing prediction models for firmness in strawberries (Fragaria × ananassa Duch.) using NIR hyperspectral imaging. From freshly harvested strawberries of “Akihime” variety at three levels of ripeness maturity, NIR (near infrared) hyperspectral images (650 to 1000 nm at 5 nm intervals) were taken and calibration models were developed using stepwise multiple linear regression. The three-wavelength (685, 865, and 985 nm) prediction model for firmness had a correlation and standard error for prediction of 0.786 and 0.350 MPa, respectively (50% to full-ripe group) . The importance of chlorophyll absorbance peak at around 680 nm and peak of water at 980 nm was also confirmed.
Rose plants (Rosa hybrida L. ‘Asami Red’) were grown hydroponically at 25°C in a 12-h day and 20°C in 12-h night cycle. The preharvest relative humidity (RH) was set at constant 60% or 85% for a constant humidity experiment, and 60 (day) /85 (night) % or 85 (day) /60 (night) % for a altered humidity experiment. The cut flower yield was greater at the constant high RH condition of 85% than at the constant low RH of 60%. Cut flowers grown at 85% RH had larger stomata in the dark than those at 60% RH. The cut roses grown at 85% showed high stomatal conductance even in the dark and poorly responded to light-dark alternation, resulting in increased transpiration and consequent decreased vase life. In altered humidity experiment, the cut flower yield was higher at 85/60% RH than at 60/85% RH. Stomatal size, responses of stomata to light-dark alternation, daily transpiration and vase life of cut flowers did not differ significantly between these two RH treatments and were almost similar to those of the roses grown at constant 60% RH. Cyclic control of day-night RH is an effective means to achieve both high yield and long vase life of cut roses.
Inorganic substances found in wastewater (i.e. industrial, agricultural, and urban-sewage runoff) constitute a form of abiotic stresses for plants, negatively impacting their growth, development, and productivity. The aim of this investigation is to establish an effective in-vitro selection system, to identify water spinach varieties displaying higher tolerance to inorganic salts and evaluated temperature. High inorganic salt concentrations (171 mM NaCI or 125 mM KH2PO4) strongly retarded chlorophyll concentration and relative water content, led to growth reduction, and decreased the seedling survival percentage of a commercial variety of water spinach. The fresh weight, shoot height, and leaf number of seedlings grown under inorganic stresses were also strongly decreased when compared to unstressed control seedlings. Moreover, seedlings grown at high temperature (30±2°C) exhibited 4-folds reduction in survival percentage compared to those grown at low temperature (10±2°C) . An in-vitro selection system was then applied to screen 54 varieties of water spinach. The results indicated that 10 varieties processed increased tolerance to high inorganic salt levels and evaluated temperature. These tolerant varieties should be further investigated in filed trials for vegetable production, contaminant absorption, and wastewater treatment. Conversely, the sensitive varieties may potentially be used as indicators for pollutant contamination in wastewater.
Quality of tomato fruits can be improved by applying water stress. To avoid the excessive yield reduction and high blossom-end rot incidence, it is highly important to apply water stress at an optimum level. In this research, a calibration model for nondestructive determination of leaf water potential (LWP) was developed using near infrared spectroscopy. A tomato leaf was cut and its spectra in transmittance mode at six different positions were immediately measured. The LWP was determined simultaneously using the pressure chamber method just after spectral acquisition. The result showed that the best calibration model was identified for spectra in wavelength range of 700-990 nm with R2=0.86 and standard error of calibration=0.076. The validation result showed that its calibration model had low bias and low SEP. By a 95% confidence pair t-test, there were no significant differences between the LWP measured using the pressure chamber method and that predicted by near infrared spectroscopy. This result showed that determination and monitoring of the LWP values using near infrared spectroscopy are possible and can be used for water stress management with high accuracy.
Effect of overnight supplemental lighting at different light intensities following natural day length on growth and leaf injury of eggplant and pepper plant was investigated. Leaf chlorosis was observed with over 35 μmol m-2 s-1 PPFD and there was no correlation between light intensity and dry matter production in eggplant. On the other hand, pepper plants grew vigorously without any injurious symptoms even at 200 μmol m-2 s-1 PPFD. Total dry weight in pepper plant increased linearly with increase in light intensity. For instance, when supplemental light intensity was 100 μmol m-2 s-1, dry weight increase was 1.57 g/plant at 3 weeks after the initiation of light treatment, which was about 2 times higher than that in natural dark control (=0.71 g/plant) . When light intensity was 200 μmol m-2 s-1, the increase rate of total dry weight was 3 times higher than that in natural dark control. Increase rate of root dry weight was 4 times, but root length in the longest root was not different between the two treatments, suggesting that the lateral root growth was promoted by supplemental lighting. When sunlight intensity was reduced by 50%, the dry weight increase rate was 1.6, 1.5 and 2.0 times for leaf, stem and root, respectively, against 1.3, 1.2, 1.3 times in non-shaded plants. These results indicate that the enhancement of dry mass production in pepper plants by overnight supplemental lighting is more profound when the daytime solar radiation is low.
Effects of 60 mM NaCI salinity, anoxia and hypoxia on the growth and transpiration of a cucumber (Cucumis sativus L. cv.‘Asomidori No. 5’ and‘Tokiwa Hikari 3A’) plant were studied in a glasshouse under sunlight and in a growth chamber. Both in the glasshouse and the growth chamber, 60 mM NaCI salinity combined with anoxia markedly suppressed growth and transpiration of plants. In the glasshouse, 60 mM NaCI combined with hypoxia also suppressed growth and transpiration of the plants, but the extent of the suppression was less marked. A parallel decline in net assimilation rate and transpiration rate as affected by salinity and anoxia was observed in the growth chamber experiment, suggesting a pivotal role in stomatal resistance to the decline in growth. The accumulation of Na and Cl under salinity was enhanced by the anoxia. Possible involvement of the concentrations of Na and Cl in the variability in fruit growth under salinity is discussed.
The mean of inoculation with arbuscular mycorrhizal (AM) fungi (Gigaspora margarita, Glomus fasciculatum, Gl. mosseae, Gl. sp. R10, Gl. aggregatum) on tolerance to anthracnose, caused by Colletotrichum gloeosporioides (CG), in strawberry (Fragaria×ananassa Duch., cv. Nohime) plants was evaluated under capillary watering conditions. Thirty days after CG inoculation, the incidence of anthracnose ranged from a minimum of 33.3% in Gl. mosseae and Gl. aggregatum plots to a maximum of 100% in non-AM (NAM) plot; the incidence varied depending on the AM fungal species. Incidence and severity of browned crown and roots became lower in AM plots than in NAM plot. As for the dry weight of plants, the AM plots showed higher values the NAM plot for both shoots and roots 11 weeks after AM fungus inoculation (just before CG inoculation) . Thirty days after CG inoculation, non-diseased AM plants had higher dry weights of shoots and roots than did diseased non-AM one. No characteristic difference in phosphorus concentration in plants appeared between non-AM and AM plots 11 weeks after AM fungus inoculation and 30 days after CG inoculation. These findings suggest that tolerance to anthracnose occurred in AM fungus-infected strawberry plants, and no close relation appeared between the tolerance and phosphorus concentration in plants.
Grafted tomato (Lycopersicon esculentum Mill.) plug seedlings were stored at 10°C for 21 d under a photosynthetic photon flux density (PPFD) of 2 ymol m-2 s-1 using mixed light from red and blue LEDs, with different percentages of blue-light PPFD (0, 2, 5, 10 and 50%) . The effect of blue-light PPFD percentage was investigated and the optimal percentage was determined based on the contents of chlorophyll (Chl) and ribulose-l, 5-bisphosphate carboxylase/oxygenase (Rubisco) in leaves on the last days of storage. Chl and Rubisco contents decreased irrespective of the blue-light treatment during storage. On the last day of storage, Chl content were greater in the 2, 5, and 50% blue-light treatments than in the 0% treatment and Rubisco content were greater in the 2-50% treatments than in the 0% treatment. The suppression of the decrease in the Chl content contributed to the preservation of the visual quality of the stored seedlings. It can be concluded that the 2, 5 and 50% blue-light PPFD were effective in preserving the quality of grafted tomato seedlings during storage at 10°C and 2, umol m-2 s-1. In a commercial operation, 2% blue-light PPFD would be optimal, because blue LEDs are expensive.