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In addition to angiosperms, most plants are able to synthesize chlorophyll (Chl)-generating green tissues in total darkness. In this study, 140 plants of the angiosperm Pachira macrocarpa were divided into five groups. Among them, one group was grown for 2 weeks under natural light conditions, whereas the others were grown in complete darkness (0 μmol m−2 s−1). Dark-grown plants were then treated with 0~6% glucose for another 8 weeks. The budding and greening ratios, ultrastructure of chloroplasts (ChlPs) of newly developed leaves, and green pigment contents of pre-illuminated mature and young leaves, and totally dark-grown newly developed leaves were measured. Results showed that glucose inhibited the budding and promoted the greening of newly developed leaves. Pre-illuminated mature and young leaves were able to synthesize green pigments during the 2 weeks of dark adaption. Dark-grown newly developed leaves contained high levels of green pigments at 2 and 3 weeks after budding. Green pigments of glucose-fed newly developed leaves had increased, whereas they had decreased in control leaves. In addition, ChlPs of dark-grown glucose-fed newly developed leaves contained both giant grana and prolamellar bodies (PLBs), usually found in shade plants and etiolated seedlings, respectively. The higher the glucose concentration was, the greater the numbers of grana, thylakoids, and PLBs. Glucose increased the green pigment contents and grana formation in newly developed leaves in a dark condition, and the mechanisms are discussed.

Background: Chlorophyllases (Chlases) are housekeeping proteins in plant cells. The dephytylating enzymes can catalyze chlorophyll (Chl) to form chlorophyllide, but the distribution of Chlases in plant cells is still an interesting debate. In this study, antibody of PmCLH2 was made and used by immunogold-labelling technique to detect the location of Chlase of Pachira macrocarpa (Pm) leaves at four developmental stages, including young, mature, yellowing, and senesced stages. Results: The transmission electron microscopy results show that Chlases were comprehensively found in portions of chloroplast, such as the inner membrane of the envelope, grana, and the thylakoid membrane of the chloroplast, cytosol, and vacuoles at young, mature, and yellowing stages of Pm leaves, but not in the cell wall, plasma membrane, mitochondria, and nucleus. Conclusions: PmChlases were mainly detected in vacuoles at the senescent stage, but a few were found in the chloroplasts. A pathway is proposed to explain the birth and death of Chl, Chlase, and chloroplasts in higher plants.

We have analyzed protein expression in the bleached small vegetative cells of synchronous Scenedesmus vacuolatus to investigate how unicellular algae lived through stress. These cells were subjected to heat treatment (46.5 &deg, C for 1h in dark condition) and then cultured under continuous illumination for 24 h. Flow cytometry analysis of the chlorophyll autofluorescence intensity of S. vacuolatus cells indicated that heat-treated cells were completely bleached within 24 h of light cultivation. Transmission electron microscopy (TEM) images showed that bleached cells maintained thylakoid membrane structure, but with lower contrast. The bleached cells regained green color after 72 h, along with a recovery in contrast, which indicated a return of photosynthetic ability. Two-dimensional gel electrophoresis (2DE) showed that the protein expression patterns were very difference between control and bleached cells. ATP synthase subunits and glutamine synthetase were down-regulated among the many differences, while some of phototransduction, stress response proteins were up-regulated in bleached cells, elucidating bleached cells can undergo changes in their biochemical activity, and activate some stress response proteins to survive the heat stress and then revive. In addition, small heat shock proteins (HSPs), but not HSP40 and HSP70 family proteins, protected the bleaching cells.

Supplementary materials and methods. (DOCX 2487 kb)

Fertilizer plays an important role in agricultural development. However, the soil environment of tea gardens has been deteriorated and the growth of tea trees has been hindered by the long-term excessive chemical fertilizer used in tea gardens. To study effects of reducing chemical fertilizer on the quality components of Tieguanyin tea leaves, Tieguanyin tea garden located in yellow-red soil was treated with three consecutive times and five recipes of chemical fertilizer. The results showed that appropriate reduction of chemical fertilizer applied in tea gardens can increase the contents of potassium and organic matter in soil, polyphenols and water extract in tea leaves. Most of the contents reach their peaks in T3 treatment, which compound fertilizer that the contents of NPK are all 15% was 412.50 kg/ha and urea was 206.25 kg/ha applied in the tea gardens, that 55% of the conventional usage by local farmers. At the same time, with the reducing chemical fertilizer applied in tea gardens, the caffeine in tea leaves was significantly decreased. Therefore, T3 treatment can improve the soil environment of tea gardens and the concentration of Oolong tea soup. Besides, it infers that the amount of chemical fertilizer in T3 treatment is a key control point for the quality of tea. The indirect influence coefficients that the chemical fertilizer effects on the contents of tea water extract, free amino acid and caffeine are all at their peaks of 5.249, 4.245 and 8.594 respectively through the changing of the soil nutrient contents. It is benefit for improving the overall quality of Oolong tea.

Anthocyanins (Ants) are water-soluble secondary metabolites that are responsible for red colour of plant leaves. To determine photosynthetic pigments, 80% acetone was used to extract Ants from Ant-containing leaves of test plants. However, using the 80% acetone extraction method can lead to interference between chlorophylls (Chls) and Ants. Porphyrins, such as protoporphyrin IX (PPIX), Mg-protoporphyrin IX (MgPP), and protochlorophyllide (Pchlide), are Chl biosynthetic intermediates and demonstrate photospectrometric characteristics similar to those of Chl. Although the ether/water extraction method was able to remove Ants interference when detecting porphyrins, the porphyrins extraction efficiency was lower than that of the 80% acetone extraction method. Low Ants levels interfered with individual porphyrin ratios, and the extent of the effect was correlated with Ants concentrations. We developed the three equations could eliminate interference by Ants when determining the porphyrin molecular percentage (%) and were comprehensively applied to all tested species of Ants-containing leaves.

The siphonous green alga Codium edule P. C. Silva (Bryopsidales, Chlorophyta) has the highest covering ratio among the macroalgae on the coral reef of Nanwan Bay in southern Taiwan, but its population in the subtidal region drastically decreases from July to September each year. The objective of this study was to determine whether the high temperature of summer could be the basis for this population decrease. Chlorophyll fluorescence measurements revealed that when the algae were incubated at 35°C (a temperature that can be reached in southern Taiwan during the summer), their photosynthetic activities were almost completely inhibited after about 8 h. The circadian rhythm of photosynthesis was disrupted at a temperature as low as 32°C. TEM studies showed that 4 h incubation at 35°C induced a decrease in turgidity accompanied by vacuole shrinkage and plasmolysis. The marked disintegrative changes, including damage to organelles, such as chloroplasts and nuclei, occurred after about 8 h, at which time central vacuoles collapsed and the cell interior was then filled with numerous small vesicles. Our results suggested that the rise in seawater temperature during the summer could be one of the major causes of the massive death of C. edule in the field.

The siphonous green alga Codium edule P. C. Silva (Bryopsidales, Chlorophyta) has the highest covering ratio among the macroalgae on the coral reef of Nanwan Bay in southern Taiwan, but its population in the subtidal region drastically decreases from July to September each year. The objective of this study was to determine whether the high temperature of summer could be the basis for this population decrease. Chlorophyll fluorescence measurements revealed that when the algae were incubated at 35°C (a temperature that can be reached in southern Taiwan during the summer), their photosynthetic activities were almost completely inhibited after about 8 h. The circadian rhythm of photosynthesis was disrupted at a temperature as low as 32°C. TEM studies showed that 4 h incubation at 35°C induced a decrease in turgidity accompanied by vacuole shrinkage and plasmolysis. The marked disintegrative changes, including damage to organelles, such as chloroplasts and nuclei, occurred after about 8 h, at which time central vacuoles collapsed and the cell interior was then filled with numerous small vesicles. Our results suggested that the rise in seawater temperature during the summer could be one of the major causes of the massive death of C. edule in the field.

To find out how microalgae cope with heat stress, the small vegetative cells of a synchronous Scenedesmus vacuolatus culture were subjected to heat treatment and then cultured under continuous illumination. The heat-treated cells were found first to enter a degenerative intermediate stage with low cellular activities almost right after the start of the cultivation, which was then followed by a revival. The changes in physiological activities and morphology of the treated cells throughout the whole period of regeneration were explored. The variations in cellular DNA content and protein composition were also investigated. Stressed cells at the end of the degeneration stage were completely bleached and were also characterized by condensed but undegraded chromatin, partially disintegrated chloroplasts but with the thylakoid membrane system retained, partially operating mitochondria, intact plasma membranes, and a dramatically changed profile of cellular proteins. All of our data indicate they were still alive but in a different physiological state than the control cells. Recovery started with regeneration of mitochondrial cristae and redispersion of chromatins. These were followed by regreening and resuscitation of chloroplasts, which often started from one part of a thylakoid membrane system and then spread out. This study provided a unicellular model for studying how plant cells react to a period of stress and recover.

Background To find out how algal cells cope with and recover from heat stress, the small vegetative cells of the synchronous Scenedesmus vacuolatus culture were subjected to a heat pretreatment (46.5°C for 1 h) followed by dark recultivation. The changes in physiological activities and morphology of Scenedesmus cells were continuously monitored throughout the course of decline and recovery. Results It was found that the heat treatment, though completely inhibited photosynthesis, did not kill Scenedesmus cells. These cells, during dark recultivation, could make a fast repair and regained the ability of proliferation. We suggest that they entered a ‘stand-by’ state, which was characterized by condensed chromatin, partially functional but morphologically altered chloroplasts, disappeared vacuoles, slightly shrunk protoplast and intact plasma membranes. These stressed cells, on the surface, seemingly were undergoing some kind of disintegration, could readily and quickly return to normal cells upon illumination. Cell death occurred only after a long period of darkness (>48 h). Conclusions Our results suggest that the recovery of algal cells from stress damage may actually proceed in two steps. The middle “stand-by’ stage normally is gone through too rapidly to be detected unless cells are kept in the dark. Electronic supplementary material The online version of this article (doi:10.1186/1999-3110-54-3) contains supplementary material, which is available to authorized users.