The shape of Florin rings and the distributional patterns of epicuticular wax of 51 species, including three varieties, in the genus Pinus were observed and classified with a scanning electron microscope. Six types of Florin rings and three types of wax distribution were observed. Florin ring structures and wax distribution correspond to subgenera. The restriction of the epicuticular waxes to the needle surface on which stomatal complexes occur suggests that the wax originates in association with the stomatal complex. In the subgenus Pinus, the Florin ring with a small opening size had little wax in the epistomatal chamber; the Florin ring with a large opening size had large amounts of wax. This suggests that the amount of wax in the epistomatal chamber and the opening size of the Florin ring are correlated with gas diffusion. Common thin, fibrillar wax, rare thick, winding wax, and occasional amorphous wax were observed. The relationships among the types of Florin rings are further discussed from the viewpoint of a developmental process.
The effects of growth temperature and winter duration on the leaf phenology of Erythronium japonicum were examined in two experiments. Bulbs wintered in the field were cultivated at 10 and 20° C and the bulbs were cultivated at 15° C after chilling treatment at 3° C for 60 and 120 days and without chilling in winter. The plants cultivated at 20° C showed significantly earlier leaf emergence, a more rapid rate of leaf extension and shorter leaf longevity than those cultivated at 10° C. The decrease in the leaf longevity at 20° C resulted from the decreases in the durations of all of the developmental, mature, and senescent phases. The bulbs without chilling treatment did not sprout leaves and those with chilling treatment sprouted leaves. The increase in the length of chilling treatment from 60 to 120 days affected leaf phenology in same manner as the increase in the growth temperature from 10 to 20° C.
Photosynthesis and transpiration were measured simultaneously, under near-optimum and constant environmental conditions, in intact leaves of plants native to the temperate forest region. A linear relationship between photosynthetic rate and stomatal conductance was found in every species tested irrespective of leaf age or season, indicating that the calculated intercellular CO concentration and water-use efficiency were fairly constant within a species. The values of intercellular CO concentration and water-use efficiency ranged from 221 to 271 μl l [Formula: see text] and 4.46 to 8.20 μmol CO mmolHO (6.24±0.90 μmol CO mmolHO), respectively. The variations in intercellular CO concentration and water-use efficiency were not directly related to photosynthetic capacities, life-forms, or microhabitat preferences. The intercellular CO concentrations found in this study were close to values reported from cultivated plants and plants native to more arid regions, suggesting a common mechanism to maintain the stomatal conductance proportional to photosynthetic capacity over a wide variety of C plants.
Effects of growth temperature and winter duration on leaf longevity were compared between a spring ephemeral, Gagea lutea, and a forest summergreen forb, Maianthemum dilatatum. The plants were grown at day/night temperatures of 25/20 degrees C and 15/10 degrees C after a chilling treatment for variable periods at 2 degrees C. The temperature regime of 25/20 degrees C was much higher than the mean air temperatures for both species in their native habitats. Warm temperature of 25/20 degrees C and/or long chilling treatment shortened leaf longevity in G. lutea, but not in M. dilatatum. The response of G. lutea was consistent with that reported for other spring ephemerals. Air temperature increases as the vegetative season progresses. The decrease in leaf longevity in G. lutea under warm temperature condition ensures leaf senescence in summer, an unfavorable season for its growth. This also implies that early leaf senescence could occur in years with early summers. Warm spring temperatures have been shown to accelerate the leafing-out of forest trees. The decrease in leaf longevity due to warm temperature helps synchronize the period of leaf senescence roughly with the time of the forest canopy leaf-out. Prolonged winter due to late snowmelt has been shown to shorten the vegetative period for spring ephemerals. The decrease in leaf longevity due to long chilling treatment would correspond with this shortened vegetative period.
The vegetative phenology of 29 alpine species, including herbaceous and woody summergreens and evergreens, was investigated. Summergreen species initiated and completed leaf growth earlier than evergreen species. The green period of leaves in summergreen plants was determined largely by the time of growth initiation. Early initiation of growth in summergreen plants contributes to the increase in photosynthetic carbon gain. Early cessation of growth in summergreens is advantageous for the growth in the following year because it leads to an increase in stored photosynthates. The growth period of leaves and stems in alpine plants correlated with the time of growth initiation more strongly than with the time of growth cessation, indicating the importance of early growth initiation for the increase in plant growth. The growth period of leaves was positively correlated with the sum of leaf lengths and the number of leaves. Herbs with a long growth period of more than 50 days had perennial shoot axes not terminated by inflorescences, suggesting a relationship between the growth period and shoot habit. Two summergreen species were completely dead by mid-September, before the air temperature decreased below 0 degrees C. The remaining summergreen species died immediately after the air temperature decreased to -1.4 degrees C in late September.
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