Experiments were conducted in controlled environment chambers to study the effects of daylength and light energy efficiency on leaf emergence and leaf growth of the main stem in barley plants. Plants were grown at constant daylengths between 6 to 24 h. The leaf number on the main stems was counted (in Haun units) every day from the emergence of the second leaf until the emergence of the seventh leaf. The area, length and dry weight were measured from the second to the sixth leaves on the main stems. The leaf emergence rate increased with the increase of daylength. But the leaf growth rate increased with the increase of daylength until an optimum daylength of 15 h and then declined under longer daylengths. The leaf emergence rate per irradiance hour was slower with the increase of daylength. The leaf growth rate per irradiance hour also decreased with the increase of daylength. The leaf emergence and leaf growth under different daylengths, but at the same light energy, were different. Both the optimum daylength for leaf emergence and for light energy efficiency to cause a barley leaf to emerge and that for leaf growth and for light energy efficiency to cause it to grow were different.

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The in vivo sensitivity to inhibition by L-malate of phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) in rapidly prepared crude extracts (within 2 min) was investigated for two CAM plants Kalanchoë pinnata and pineapple (Ananas comosus (L.) Merr. cv. Smooth-cayenne N67-10) . The phosphorylation process may not occur in pineapple PEPC. Variations were also observed in apparent kinetic properties and molecular mass as well as subunit composition of PEPC from these plants. Two different subunits (major polypeptide 112 kDa and minor polypeptide 119 kDa) were separated from day and night forms of PEPC from K. pinnata but only one identical subunit (107 kDa) from pineapple. The integrity of both forms of in vivo PEPC from these plants was demonstrated by Western blot analyses using anti-N-terminus antibody. K. pinnata lost malate sensitivity about 87% whereas pineapple PEPC lost only 21% sensitivity at night in the presence of 2 mM L-malate. The apparent K_i (L-malate) was 6.4-fold higher in phase I (5.8 mM) than that in phase III (0.9 mM) from K. pinnata but it was only 1.0 and 0.5 mM for day and night PEPC respectively from pineapple. These findings suggest phosphorylation process may not be the major regulatory mechanism in pineapple PEPC.

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The CO₂ dependent O₂ evolution during the light period, at which the exogenous CO₂ uptake was suspended, in 12 CAM plants (including pineapple (Ananas comosus) ) was evaluated with a gas-phase oxygen electrode. At 5% CO₂, the rate of photosynthetic O₂ evolution in pineapple was saturated at 1 500 μmol m^-2 s^-1 PPFD and the maximum rate was 60 μmol m^-2 s^-1, which was 10 times those obtained at ambient CO₂ conditions with the CO₂ exchange system and significantly higher than the other CAM plants. At the saturated PPFD, the O₂ evolution in pineapple substantially increased with increasing CO₂ concentration up to 3% and decreased above 4%. However in the other CAM plants, such increment was small. By the use of a novel compensating CO₂ gas exchange system, the rate of CO₂ exchange in pineapple at very high CO₂ was measured and found the enhancement of CO₂ uptake in both light (Phases III and IV) and dark (Phase I) periods. Based on the results obtained, possibilities of the further increases in CO₂ uptake in CAM plants, especially of pineapple, are discussed in terms of stomatal functions and malate storage capacities.

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The gas exchange rates of C_3- and C_4-grass leaves at low and high vapor pressure difference (VPD) conditions were measured and demonstrated the effects of anatomical and morphological features of the leaves, i.e. stomatal frequency and size and interveinal distance (IVD), on gas exchange characteristics. When the photosynthesis type was ignored, there was a positive correlation between stomatal frequency and stomatal conductance. However, there was less significant correlation between stomatal frequency and transpiration rate when plotted species within the same photosynthetic pathway. There was a negative correlation between stomatal frequency and net photosynthetic rate, suggesting that CO₂ diffusion process from ambient to intercellular space was not much affected by the stomatal morphology, instead that a consequence of biochemical differences in photosynthetic characteristics of the mesophyll was more important. An increase in IVD significantly decreased net photosynthetic rate and water use efficiency (WUE) . In addition to the regulation of CO₂ concentrating mechanism in Kranz cells of the C₄ subtypes, a rapid translocation of photosynthate from bundle sheath cells to the phloem in grasses with C₄-MS type (NADP-ME) may contribute to maintain their high performances in photosynthesis and WUE through shorter IVD.

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Effects of salinity stress at various fruit development stages from flowering to harvest on yield and fruit quality were investigated in single-truss tomato plants grown in hydroponics. Salinity stress was imposed by applying the concentrated drainage (EC 5.0 dS m^-1) instead of the standard solution (EC 1.2 dS m^-1) . Rates of water uptake and leaf photosynthesis were significantly inhibited by salinity at various growth stages. The earlier the salinity stress was applied, the lower the fruit weight and the higher the soluble solids content. Fruit fresh weight was severely decreased by salinity, whereas, fruit dry weight was less affected. When salinity was applied too early, there was a high rate of occurrence of blossom-end rot. Salinity stress beginning several days before harvest markedly prevented fruit cracking. From these results, we concluded that salinity was essentially a form of water stress, and that the resultant improvement of fruit quality and prevention of fruit cracking would be caused by the inhibition of water influx into the fruit. In single-truss tomato system, growers can easily produce various tomato fruit with different sizes and soluble solids contents by varying the time of application of the concentrated nutrient solution.

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The mericlonedCymbidiumLovely Angel‘The Two Virgins’is known among commercial growers as a difficult cultivar in which to induce leads. At Yatsugatake Experimental Farm, Yamanashi Agricultural Experimental Station (Takane, Kitakoma, 955 m elevation), we studied the effects of autumn and winter light and temperature management on the number of leads in this cultivar. Variations in both light intensity and night temperature showed great effects on theCymbidiumplants. Low night temperature promoted the development of leads, while low light intensity retarded lead development. The number of leads was not correlated with obvious growth characteristics such as the number of leaves or leaf length.

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To clarify the allelopathic system of lemon balm (Melissa officinalisL.), purification and isolation of allelopathic substances was undertaken in acetone extract of the shoots of the 30-d-old plants. Three growth-inhibiting substances were found in the neutral fraction of the extract after silica gel column chromatography, and most active substance was further purified and isolated by thin layer chromatography, C₁₈Sep Pack cartridge and reversephase high performance liquid chromatography. This substance inhibited the growth of cress (Lepidium sativunL.) at concentrations greater than 0.3 μg mL^-1and the concentration required for 50% growth inhibition was 2.9μg mL^-1. These results suggest that lemon balm shoots may contain at least three growth-inhibiting substances, which may be released into the environment, either as exudates from living tissues or leachates from residues of the plant, and may act as allelochemicals to neighboring plants.

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Continuous measurements of solar radiation (R_s), net radiation (R_n) and photosynthetically active radiation (PAR) were conducted in Kohn Kaen, Northeast Thailand characterized as dry-and-wet tropics over 4 years (R_sandR_n) and a year (PAR) . Monthly mean solar radiation was more than 15 MJ m^-2over a year with its minimum occurring in dry season. Monthly mean net radiation in the dry season was a half of that in the rainy season. On daily basis, PAR/R_s-ratio changed from 1.81μmol MJ^-1in January to 2.08μmol MJ^-1in July. Equations for converting instantaneous and daily solar radiation to PAR were empirically derived with daily mean water vapor pressure as a parameter.

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