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资助项目
6 could use lots of photosynthates, but contributed little to the accumulation of biomass. 4. Photosynthetic rate of P. armeniacum decreased a little at the noon, and the highest photosynthetic rate was observed at 10:00h in the greenhouse. The variation of photosynthetic rate was in the same trend as stomatal conductance. Higher relative humidity seemed to be the key for higher photosynthetic rate in P. armeniacum. 5. The photosynthetic capacity of C. flavum was statistically larger than that of P. armeniacum. The lower leaf photosynthetic capacity of P. armeniacum was related to its lower leaf nitrogen concentration,leaf phosphorus concentration and enzyme activities. Meanwhile, the extremely lower stomatal conductance and internal mesophyll conductance might greatly limit the photosynthetic capacity of P. armeniacum. The lower stomatal conductance and photosynthetic rate of Paphiopedilum might partially caused by the lack of chloroplasts in the guard cell of Paphiopedilum. Compared with C. flavum, P. armeniacum was more fond of shade environment.6. The short longevity leaf of Cypripedium had bigger photosynthetic capacity and greater potential for fast growth. But the longer LL of Paphiopedilum enhanced nutrient conservation which could compensate its lower photosynthetic capacity. The short longevity leaf of Cypripedium usually had higher photosynthetic rate per unit leaf mass and dark respiration rate, and photosynthetic capacity decreased fast with leaf age. However, for Paphiopedilum, the situation was the opposite. 7. Compared with Cypripedium, Paphiopedilum had higher water use efficiency and lower photosynthetic nitrogen use efficiency. 8. The leaf of Paphiopedilum had higher leaf construction cost and longer repayment time than that of Cypripedium. The leaf structures and physiological functions of Paphiopedilum and Cypripedium reflected the adaptation to their habitats. The leaf morphological and physiological evolution of Paphiopedilum was related to water and resource-conserving traits in the karst habitat. The leaf traits of Cypripedium were the adaptation to the environment rich in water and nutrients but easy to change with seasons.Our results provided evidence of divergent evolution of congeneric orchids under natural 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and Cypripedium，known as slipper orchids in horticulture, belong to the subfamily Cypripedioideae of the Orchidaceae. Although they are closely related phylogenetically, there are significant differences in leaf traits and geographical distributions between two genera. This dissertation includes the following sections: (1) the leaf functional traits were compared in six species of the two genera; (2) the physiological responses of P. armeniacum to different water regimes, light regimes and low temperature; (3) the leaf phenotypic plastics of C. flavum in response to the different light condition and the photosynthetic characteristics of three Cypripedium species during sexual reproduction. The aims are to understand the convergent and divergent evolution between the two genera in leaf traits and their adaptive significances, and the leaf plastic responses to different levels of resources. Such information could provide scientific basis for conservation and domestication of Paphiopedilum and Cypripedium. The results are given below:1. Compared with Paphiopedilum, Cypripedium showed significantly higher photosynthetic rate (Pmax), leaf nitrogen content (Na), photosynthetic nitrogen utilization (PNUE), the fractions of leaf nitrogen partitioning in carboxylation (PC) and bioenergetics (PB), specific leaf area (SLA), ratio of leaf chlorophyll a and b (Chla/b), but significantly lower leaf construction cost (CC) and the ratio of leaf carbon content to leaf nitrogen (C/N). These leaf traits of Cypripedium are considered as the adaptation to short growing period and rich soil nutrients in the alpine habitats. Conversely, the long life span, low Pmax and mesophyll conductance (gm) but high SLA, CC and C/N in Paphiopedilum indicated that the adaptation to low-light, limited-nutrient habitat in the limestone area. As a sympatric species of Paphiopedilum, C. lentiginosum not only kept phylogenetically leaf traits of Cypripedium, suchas stomatal conductance (gs), Pmax, PNUE and dormant in winter, but also possessed many leaf traits which is similar to that in Paphiopedilum, such as relative stomatal limitations (RSL), gm, the ratio of leaf chlorophyll a and b (Chl a/b), fraction of leaf nitrogen allocated to light-harvesting components (PL). These results indicated the convergent and divergent evolution of Paphiopedilum and Cypripedium in leaf traits.2. Paphiopedilum. armeniacum exhibited a high plasticity of leaf photosynthetic function in response to different light regimes, but the responses changes with the time. Due to grow under low light habitat, P. armeniacum grown under 50% shade (HL) had the significantly lowest Pmax than the plants grown under 75% shade (ML) and 95% shade (LL) after six months. However, after twelve months, the Pmax of the plants grown under HL increased significantly and then became the highest one among three levels of light. It is also found that leaf dry mass per unit area (LMA), leaf stomatal conductance (gS), internal mesophyll conductance (gm), the fraction of leaf nitrogen partitioning in photosynthetic carboxylation (PC), bioeneretics (PB) were greatly influenced by irradiance. The plants grown under HL increased gS, gm, PC, PB to increase Pmax. In addition, the plants grown under HL had the highest ratio of total chlorophyll content to total Carotenoid content (Car/Chl) while the plants grown under LL had the lowest ratio of leaf chlorophyll a and b (Chl a/b). As a result, plasticity of leaf photosynthetic physiology of P. armeniacum in response to different light regimes depended largely on leaf nitrogen partitioning and leaf structure. As for the numbers of flowering and fruiting, ML was the best light level.3. The responses of P. armeniacum to different water regimes were not significantly different. But the Pmax and the maximum photochemical efficiency of PSⅡ (Fv/Fm) decreased with the increased frequency of watering. The reasons were that the plants have high respiration rate (Rd) and make more use of light energy to oxidation cycle. The plants watered every eight days (MW) and every twenty days (LW) had higher Pmax than the plant watered every four days (HW) mainly because of the higher PC and PB. Besides, the leaves of P. armeniacum had excellent property for holding water also contributed to the high photosynthetic capacity.4. Paphiopedilum. armeniacum was very sensitive to the low temperature. The plants significantly decreased photosynthetic capacity after grown under 4℃ for three days and the photosynthetic machinery was destroyed after fifteen days. The photosynthetic capacity of P. armeniacum exhibited no change at 10℃ and 15℃.5. Cypripedium flavum of four habitats (DB, XRD, XZD and TSQ) with different light intensity exhibited different photosynthetic characteristics after transplanted to the same environment in Kunming. Among the habitats, the light intensity of DB was the highest while XRD was the lowest. The light intensity of XZD and TSQ were not significantly difference. Among all the plants in Kunming, the plants of DB had the significantly highest Pmax but the plants of XRD had the lowest Pmax. The light saturation point (LSP) and photosynthetic nitrogen use efficiency (PNUE) agreed well with the light intensity of four habitats and contributed to the high Pmax of DB. The LMA, Chl and leaf nitrogen content were not different among all the plants. C. flavum exhibited sensitively response to the change of light in leaf construction while kept the plasticity of leaf photosynthetic characteristics which developed from its own habitat.6. The photosynthetic capacity of C. tibeticum and C. flavum were significantly increased at the flowering stage. For these two species, the significantly increased Amax were closely related to the maximum carboxylation rate by ribulose-1, 5-bisphosphate carboxylase/oxygenase (Vcmax), photon saturated rate of electron transport (Jmax), the rate of triose phosphate utilization (TPU) and actual quantum efficiency of the photosystem II photochemistry (ΦPSII) respectively. However, flowering almost did not affect the photosynthetic capacity of C. guttatum. C. guttatum had the smallest plant size, the leaf area, the volume of labellum and the volume of fruit, but the biggest fruit volume per leaf area among three species. These results indicated that for C. flavum and C. tibeticum there were a physiological mechanism in photosynthesis to compensate the cost of flowering as well as increased resource acquisitions, which would be beneficial to the survival or future flowering of the plant. C. gutattum could keep a steady photosynthetic capacity during life history. This kind of pattern could decrease the effect of the reproductive costs as much as possible. In contrast to C. flavum and C. tibeticum, C. gutattum possessed a more economical and effective reproductive pattern which maybe related to its wider distribution.In conclusion, Paphiopedilum and Cypripedium have significantly different leaf traits which agree well with their habitats and there is a divergent and convergent evolution between the two genera. P. armeniacum is much tolerant and responsive to varying water and light availability but very sensitivity to the low temperature. Confronting the suddenly change of light environment, C. flavum can respond sensitively to the change of light in leaf construction but the plasticity of leaf photosynthetic characteristics which developed from its own habitat can hold for the next growing season. In contrast to C. flavum and C. tibeticum, C. gutattum possesses a more economical and effective reproductive pattern which maybe related to its wider distribution. The study of the relationship between the two genera, the response and tolerance to the environmental factors of the two genera are important for understanding the adaptation and evolution of the 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