Hydrogen gas, one of the best candidates for clean and renewable energy, can be produced by microalgae that can use solar energy to cause photolysis of water. This study screened H 2 -producing indigenous green microalgae under sulphur (S-) deprivation, simultaneous nitrogen (N-) limitation and S-deprivation, or simultaneous N-limitation and phosphorus (P-) deprivation. Sequences of 18S rDNA and ITS in conjunction with morphological characteristics were used to identify the algae. We report that Chlorella lewinii, Micractinium sp., Coelastrella sp., and Monoraphidium sp. have the ability to produce H 2 . The increase in H 2 photoproduction when N is limited seems to be a universal phenomenon in most tested strains of Chlorella, in all strains of Chlamydomonas, but in no strain of Coelastrella, Micractinium, or Scenedesmus. Chlorella sorokiniana KU204 produced H 2 (46 ml/l) under S-deprivation. This strain exhibited the highest H 2 -producing ability (1.30 ml l −1 h −1 ) and accumulated up to 90 ml/l under simultaneous N-limitation and S-deprivation. Interestingly, C. sorokiniana KU204 could also produce H 2 under simultaneous N-limitation and P-starvation (69 ml/l). The induction time to reach an anoxic state by most tested strains of Chlorella, but not Chlamydomonas, was shorter under simultaneous N-limitation and S-deprivation than under S-deprivation. In addition, those strains of Chlorella exhibited high H 2 photoproduction under simultaneous N-limitation and S-deprivation. A few Chlorella strains were unable to reach an anoxic state during the experiment. However, such regularity is not found in Chlamydomonas. The results indicate that the mechanism of H 2 photoproduction in Chlorella may differ from that in Chlamydomonas.

Paclobutrazol (PBZ) is a growth regulator used to control vegetative growth, stimulating the reproductive capacity of plants. PBZ has been widely marketed throughout the tropics to stimulate mango flowering. In the recent years, many reports showed that application of PBZ by soil drenching can cause permanent stunting of flushes, the vegetative and root growth of mango was reduced. The aim of this work was to determine the effects of PBZ on flowering of mango by foliar application. The commercial mango cultivar 'Namdokmai-sitong' was used in this study. The experiment was analyzed as a completely randomized design. There were 4 replications with 10 treatments. Foliar application at 15 days after pruning with PBZ at 0, 500, 1,000, 1,500 and 2,000 mg./L and repeated at 30 days with 0 and 1,000 mg./L. There was significant difference on the time to flowering, percentage of flowering shoots and panicle length. The trees receiving the PBZ at 2,000 mg/L were exhibited stunting of flushes and panicle malformation. This study suggests that the multiple foliar application of PBZ was effective in promoting flowering in 'Namdokmaisitong' mango, can help early flowering and higher percentage of flowering shoots.

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Photosynthetic hydrogen (H 2 ) production by green algae has fascinated biologists and energy experts, due to the potential application of this process for renewable energy. In this study, H 2 photoproduction and PSII photochemical activities were investigated in Chlorella sorokiniana exposed to simultaneous nitrogen limitation and sulfur (S-) and/ or phosphorus (P-) deprivation. Under S-deprivation, C. sorokiniana produced about 48.2 mL L -1 of H 2 . Moreover, simultaneous nitrogen limitation (0.7 mM NH 4 Cl) and sulfur-and/or phosphorus-deprivation significantly increased H 2 production of C. sorokiniana over that of S-deprivation alone. Maximum H 2 outputs of 77.3, 98.1 and 125.1 mL L -1 were obtained in the N-limited cultures exposed to P-deprivation (TAP-P), S-deprivation (TAP-S) and simultaneous S-and P-deprivation (TAP-S-P), respectively. The average rate of H 2 production for the N-limited culture exposed to TAP-P, TAP-S and TAP-S-P was 1.07, 1.36 and 1.50 mL L -1 h -1 , respectively. Interestingly, the H 2 inducement time in the culture subjected to simultaneous N-limitation and S-and/or P-deprivation was much shorter than that of traditional S-deprivation. The photosynthetic inhibitors, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and 2,5-dibromo-3-methyl-6-isopropylp-benzoquinone (DBMIB) repressed H 2 production in TAP-S-P (0.7 mM NH 4 Cl) medium by 68.04% and 98.65%, respectively. The conditions of simultaneous N-limitation, S-and P-deprivation provided another efficient method for inducing H 2 production in C. sorokiniana. In addition, we also found that two-thirds of the required electrons were generated from the splitting of H 2 O in PSII and that the remaining onethird possibly came from some other substrate catabolism.

In tropical countries, low seed setting is a major problem when cultivating lotus (Nelumbo nucifera Gaertn.). This study determined seed setting in six wild lotus cultivars: Sai Rung (SR), Sam Roi Yot (SY), Klong Yong, Puttha Monthon (PM), Rachine (RC), and Nakhon Sawan (NW). In nature, the seed-setting rates range from 52-78%. From a stigma removal study, only a 53% seed-setting rate by self-pollination was recorded in the SR cultivar. This result was similar to the seed setting of self-pollinated PM, although high viability of PM pollen from day 2 full bloom flowers was observed. Self-incompatibility was studied in RC and NW cultivars. The indices of self-incompatibility of RC and NW were both 96% indicating that self-incompatibly affects low seed setting in these two cultivars. The results showed that the low seed-setting rate also came from seed abortion. A high value of self-incompatibility was observed in RC and NW cultivars, but not in the other cultivars studied.