Increasing Irradiance Levels Research Articles

Influence of tidal location on morphology, photosynthesis and pigments of the agarophyte, Gelidiella acerosa, from Northern Philippines

The red seaweed agarophyte, Gelidiella acerosa (Forsskal) (Feldmann& Hamel) was collected from tidepools, high intertidal rocks. and shallow subtidal are as along a reef flat in Ilocos Norte, northern Philippines. The three populations were compared during the summer (dry) and rainy (wet) seasons to determine changes in morphology and photoacclimation capacity as possible use in mariculture. During summer months (February toApril) after exposure to environmental extremes (i.e. the highest percent of minus tides during daylight, high light regimes, desiccation, and solar bleaching), the populations differed in their morphologies and responses to increasing irradiance levels (P–I curve). Tidepool plants were the tallest, bushiest, and with increased diameter of cortical cells; while,high intertidal plants were the shortest, with sparse branching pattern and decreased diameter of cortical cells. Although their saturation irradiances indicated shade tolerance (Ik = 52 − 112 µmol photon m -2 s-1). their differential light saturation curves (P-I curves) suggested a capacity to acclimate to ambient light regimes. For example, plants from the high intertidal zone showed higher photosynthetic rates and saturation irradiances, slightly lower initial slopes of the P-I curves and levels of light harvesting accessory pigments, rphycoerhythrin (R-PE) and rphycocyanin (R-PC), after being exposed to higher light regimes. In contrast, plants from tidepools and shallow subtidal areas had lower photosynthetic rates and saturation irradiances, slightly steeper initial slopes of the P-I curves and levels of R-PE and R-PC, having been exposed to lower light regimes. During the rainy months (June to November) no significant responses in these parameters were recorded. Comparison of the P-I responses of vegetative and tetrasporic plants showed these to vary with season. The data suggest that when plants became reproductive their physiological fitness either was unchanged or slightly enhanced. These results indicate that all three populations of G. acerosa could be used as seed stock for mariculture.

Influence of irradiance level on flowering and male sterility induced by short days in Salsola komarovii Iljin

Flowering and the male sterility induced by short days (SD) in Salsola komarovii Iljin (Chenopodiaceae) were studied anatomically and physiologically. A light-microscopic observation found that the male-sterile flowers had traces of stamens. The development of stamens ceased at the last stage of meiosis of pollen mother cells, and then vacuolated and degenerated. Flowering occurred earlier, and the number of flowers increased with increasing irradiance levels. On the other hand, the irradiance affected male sterility only slightly, and most of the flowers were male sterile even under high irradiance. The results indicate that irradiance interacts with photoperiod in different ways in regulation of flowering and male sterility within the same species.

Mechanism of degradation and crosslinking of polyurethane when irradiated by gamma‐rays

AbstractWe conducted a study to clarify the mechanism of crosslinking and degradation of thermoplastic polyurethane (PU) when irradiated with gamma‐rays. Changes in molecular weights as a result of gamma‐ray irradiation, the UV absorption, the amount of PUs with amino groups, and the elution of oligomers to an organic solvent were determined to estimate characteristic changes in PU caused by irradiation. The amount of PUs with primary amino groups as a degradated PU products at p,p′‐methylenediphenyl diisocyanate–1,4‐butanediol (MDI–BU) hard segments increased linearly with increasing irradiation level. The amount of this products by gamma‐ray irradiation was approximately 10–20% of the calculated amount, indicating that predominant degradation occurred at polytetramethyleneglycol (PTMG) soft segments (about 80–90% of the degradation). Characteristic differences were seen in crosslinking between non‐chain‐extended thermoplastic PUs based on the molecular weights of PTMG, (Mw of PTMG = 640–2800). The crosslinking ratio is linearly proportional to the molecular weights of PTMG, indicating that crosslinking at PTMG soft segments was major (the ratio of crosslinking at PTMG was more than 90%). Methanol extract of PU indicated elution of PU oligomers ranging from 13 to 1 as a polymerization degree.

Degradation and cross-linking of polyurethane irradiated by gamma-rays

A study has been conducted to clarify the mechanism of cross-linking and degradation of thermoplastic polyurethane (PU) when it is irradiated with gamma-rays. Changes in molecular weight, UV absorption, and the amount of PUs with amino groups caused by irradiation were determined. Thermoplastic PU chain-extended with 1,4-butanediol (BU) showed degradation, while thermoplastic PU nonchain-extended with BU predominantly showed cross-linking as a result of gamma-ray irradiation. The amount of PUs with primary amino groups increased linearly with increasing irradiation levels and the amount was approximately 10 μ equivalents per gram of sample at the highest level. This amount corresponded to approximately 20% of the amount calculated, indicating that degradation occurred partly at 4,4′-diphenylmethane diisocyanate (MDI)-BU hard segments. The molecular weight of degraded PUs was approximately 1 2 to nearly 1 3 that of the original Mw. This Mw change was greater than that estimated from the amount of PU with primary amino groups produced, indicating that degradation occurred predominantly at polytetramethyleneglycol (PTMG) soft segments (about 80 to 90% of the whole degradation). Characteristic differences were seen in cross-linking between nonchain-extended thermoplastic PUs based on various molecular weights of PTMG (Mw of PTMG 640 to 2800). PUs fabricated from PTMG of greater molecular weight showed greater cross-linking. The cross-linking ratio is linearly proportional to the molecular weight of PTMG, indicating that cross-linking at PTMG soft segments was predominant (the ratio of cross-linking at PTMG was more than 90% of the total cross-linking). In gamma-ray irradiation both cross-linking and degradation occurred predominantly at PTMG soft segments.

Effects of Sodium Nitrite, Sodium Nitrate and DL, Alpha-Tocopherol on Properties of Irradiated Frankfurters

Frankfurters were manufactured to contain certain combinations of curing ingredients (sodium nitrite, sodium nitrate and DL alpha-tocopherol). Some frankfurters were made to contain in the finished product 0% added moisture, others were made to contain 10% added moisture, some frankfurters were not irradiated (0-megarad), others were irradiated with either 0.8 or 3.2 megarads (Cobalt-60 radiation source). Use of DL, alpha-tocopherol (at a level of 206 ppm) was associated with greater processing shrinkage, more off-flavor and less overall palatability (P<0.05). The most desirable external and internal cured color and firmest texture was in frankfurters made with 50 ppm of NO2 or with 100 ppm of NO2, irrespective of irradiation level. Use of irradiation (0.8 or 3.2 megarads) on frankfurters made without nitrite or nitrate did not improve visually determined cured color but did improve this color when determined spectrophotometrically; nevertheless, cured color of irradiated frankfurters made without use of nitrite or nitrate was not comparable to that of non-irradiated or irradiated frankfurters made with 100 ppm NO2. Irrespective of added moisture or curing ingredient combinations, significant differences (P<0.05) in palatability traits were associated with increasing irradiation levels (0, 0.8 or 3.2 megarads). Off-flavor increased, texture was less firm and overall palatability was less desirable as irradiation level increased. Low-dose irradiation (⩽1 megarad) may be feasible for enhancing the palatability traits of frankfurters containing lower levels of nitrite (lower than 156 ppm) but it appears that the correct irradiation level would be lower than the 0.8 megarad used in this study.