Seed bank and regeneration dynamics of <Emphasis Type="Italic">Emmenopterys henryi</Emphasis> population on the western side of Wuyi Mountain,South China

Emmenopterys henryi Oliv. (Rubiaceae) is an endangered tree species that is native to China. The wild populations of E. henryi have declined rapidly because of its poor natural regeneration, but the actual regeneration processes are not yet understood. In field tracking surveys and experiments in the Wuyishan Nature Reserve in Southeast China to determine the most important stage that affects the regeneration process, seed bank characteristics, seed germination, and seedling growth dynamics were studied in the typical habitats of E. henryi, Phyllostachys pubescens and broad-leaved forests. Results showed that in both P. pubescens and broad-leaved forests, more than 70% of the E. henryi seeds were distributed in moss and litter layers, and few were found in the soil beneath them. However, seed germination in the soil layer was significantly higher than in the moss and litter layers. Seed density, overall seed quality, and germination rate in the broad-leaved forest were significantly higher than in P. pubescens forest. Seed germination was highest in the microsites around the edge of the crown projection area of E. henryi mother trees. The order of survival rate of the seedlings on different ground surfaces was soil > moss > litter. In both habitats, the average seed density was 24.9 seeds m^?2, and the total germination rate was less than 3.5‰. However, seedlings developed from only 1% of the germinated seeds, indicating that the seed germination is the most important stage in the natural regeneration of E. henryi.     

Application of oxygen-sensing technology to measure seed quality of <Emphasis Type="Italic">Ginkgo biloba</Emphasis>

Germination tests are currently the most widely used method to evaluate seed quality of Ginkgo biloba L., but they are time-consuming and labor intensive. Oxygen-sensing technology, based on the principle of fluorescence quenching to detect oxygen and assess seed quality was used to rapidly evaluate seed quality of two varieties (Shandong Tancheng 202 and Zhejiang Dafoshou) of G. biloba from five mother plants. Fifteen samples of three vigor levels were produced by accelerated aging treatments. This process was applied in duplicate. A portable oxygen-sensing detector was employed to measure oxygen content during seed germination in a closed system at 25 °C each day until day 14. Four oxygen metabolism indices were calculated: oxygen consumption index, oxygen consumption rate, critical oxygen concentration, and theoretical germination time (T _GT). Additionally, we tested laboratory germination and field emergence. The results of a one-way analysis of variance and correlation analysis showed that T _GT was the candidate index to evaluate seed quality of G. biloba. Therefore, the T _GT value was used to validate the reliability of oxygen-sensing evaluation for Zhejiang Dafoshou seeds kept under four storage conditions. The trend in the change in oxygen metabolism agreed completely agreement with that of seed germination under all storage conditions. The oxygen-sensing test reliably and rapidly assessed seed quality of G. biloba. The germination rate of Zhejiang Dafoshou was accurately predicted by T _GT.     

Germination and early seedling growth of <Emphasis Type="Italic">Pinus densata</Emphasis> Mast. provenances

We studied seed germination and early seedling growth of Pinus densata to explore the range of variability within the species and to inform afforestation practices. Phenotypes were evaluated at a forest tree nursery under conditions that support Pinus yunnanensis, one of the presumed parental species of P. densata. Seeds were collected from 20 open-pollinated trees within each of eight autochthonous populations representing the natural distribution of P. densata in China to assess variation in germination traits and early seedling growth, and to examine the relationships among these traits. Results showed that seeds from all populations germinated and seedlings established successfully. There were significant differences among populations in 13 of 14 traits evaluated. Seed germination and early seedling growth were strongly related to seed size and seed weight. Bigger seeds germinated earlier and faster than small seeds, and seedling size was positively correlated with seed size. Some germination traits were strongly and significantly correlated with climatic variables associated with the provenance of the studied populations. Based on these observations, we conclude there were large, significant, and biologically important differences among P. densata populations in seed germination and seedling growth traits. The observed variability probably reflects a high degree of adaptive differentiation among populations that is likely to be relevant for future afforestation.     

Variation in seed traits and seedling vigour of <Emphasis Type="Italic">Cordia africana</Emphasis> Lam. provenances in Ethiopia

Cordia africana is a very important indigenous tree species for timber and other products and services in Ethiopia. Seed traits and seedling vigour of seeds from 12 provenances of the species were compared. Mean seed mass for each provenance was assessed for 1000 seeds in 10 replications, and seed length and width were measured for 100 seeds in four replications per provenance. Germination was assessed in a glasshouse taking 400 seeds from each provenance. Root collar diameter and height of 440 seedlings grown in a nursery for 290 days in Addis Ababa were measured. Seed length, seed width, seed mass, and shoot height and root collar diameter of seedlings showed significant differences (P < 0.001) among provenances. Correlation analysis between seed and seedling traits and environmental variables revealed significant positive correlations between seed width and germination percentage, seed width and altitude, seed width and longitude and seed length and latitude. Negative correlations were obtained between seed width and temperature, seed width and rainfall, seed mass and temperature, and germination and temperature of the seed source. As expected, differences in seed trait did not explain the variability in seedling vigour. Determining quantitative variations in seed traits and seedling vigour among provenances and the patterns along environmental gradients are essential for informing decisions on the tree improvement programme of the species.     

Variations in seed size and seed mass related to tree growth over 5 years for 23 provenances of <Emphasis Type="Italic">Quercus acutissima</Emphasis> from across China

The origin of a seed strongly impacts its traits, and both origin and seed traits influence seed germination and seedling development. However, in many instances, this effect on the seedling does not persist into adulthood, and little is known about how seed traits and original environment affect seedling/tree growth over time. In this study, seed size, seed mass, seedling/tree growth and origins were collected and determined for 23 provenances of Quercus acutissima from across China. Origin variables correlated well with seed size and seed mass. In stepwise multiple regressions, a longitudinal aridity index explained 49.2–68.7% of the total variation in seed size and mass, while only seed width was correlated with seedling/tree height (H) and diameter at the ground (D) from seed traits and origins. The total variance in H and D explained by the models decreased over time, for example, the R ² value of the models for H declined from 0.477 in the first year to 0.224 in the fourth year; no models was significant in the fifth year. These results indicate that seed size, regulated by the longitudinal aridity index strongly impacted seedling and tree growth, but the strength of the influence decreased over time, and disappeared after 4 years.     

Improving the collection and germination of West African <Emphasis Type="Italic">Garcinia kola</Emphasis> Heckel seeds

Garcinia kola is highly used as chew-stick for dental care in West Africa, but it is nearly commercially extinct in nature. To help find methods to increase rate and percentage of germination, we investigated its seed germination responses by using several collections and pre-treatments. Seeds processed from 6-week old green fruits did not germinate, whilst those of 10-week old partly-mature, at the intermediate stage through full development, germinated 46%. Seeds from orange mature fruits reached maximum 54–62% germination. Radicles emerged 6 weeks after sowing and normal germination with emergence of the primary single shoot growth occurred after 12 weeks. There was no significant difference (P ≥ 0.05) between germination responses of seeds from Ghana and Cote d’Ivoire. Seeds did not germinate when dried to below ca. 30% MC. De-coating seeds or soaking intact seeds in a 70% ethanol solution increased germination to 82–92%, and also increased germination rate; however germination was not uniform. Because difficulties in germinating these seeds stem from the physical presence of the seed coats and the slow growth of the embryos contained therein, we recommend that fresh seeds from mature fruits be de-coated and immediately sown in preferably, an aerated medium (e.g., sawdust) for cultivation.     

Understanding biological characteristics of <Emphasis Type="Italic">Acacia melanoxylon</Emphasis> in relation to fire to implement control measurements

Key message

Acacia melanoxylon produces abundant seeds leading to large seed banks in the soil. These seeds display a large viability and their germination is stimulated by heat. To control the populations, it is necessary to remove adults and young individuals, and to prevent seedling establishment after fire occupying the space with rapid growth and high competitive native species.

Context

Acacia melanoxylon displays a widespread distribution in South West Europe, and an improved knowledge of its reproductive characteristics is required in order to control its expansion.

Aims

This experiment was designed to provide useful indicators for an efficient management of A. melanoxylon populations based on its biological cycle in relation to fire.

Methods

We explored the reproductive biology of A. melanoxylon, from seed dissemination—–quantifying seed rain over a year, their germination with and without fire—the seedling and sapling banks and the structure of the adult population. We analysed the effects of fire, seed maturation and scarification on the viability of seeds and the stimulation of seed germination in the aerial seed bank and in the different strata of the soil seed bank.

Results

Our results indicate that A. melanoxylon produced millions of seeds per ha and per year, half of which germinated and the other half went to the soil seed bank, maintaining the viability many years. The germination was the most critical step in the population dynamics of this species, and fire stimulates germination up to 90%.

Conclusion

A. melanoxylon adults and seedlings removal, followed by colonization of rapid growth and high competitive native species that cover the ground very quickly would be a good control action.

     

Mating patterns of the gum arabic tree (<Emphasis Type="Italic">Acacia senegal synonym Senegalia senegal</Emphasis>) in two different habitats

Understanding the variation of mating patterns in disturbed habitats provide insight into the evolutionary potential of plant species and how they persist over time. However, this phenomenon is poorly understood in tropical dryland tree species. In the present study, we investigated how Acacia senegal reproduces in two different environmental contexts in Kenya. Open-pollinated progeny arrays of 10 maternal trees from each environmental context were genotyped using 12 nuclear microsatellite markers. Overall, A. senegal displayed a predominantly allogamous mating pattern. However, higher multilocus outcrossing rate (tm) was found in Lake Bogoria (tm = 1.00) than in Kampi ya Moto population (tm = 0.949). Higher biparental inbreeding (t _m  ? t _s  = 0.116) and correlation of outcrossed paternity (rp = 0.329) was found in Kampi ya Moto than in Lake Bogoria population (t _m  ? t _s  = 0.074, rp = 0.055), showing the occurrence of mating among relatives. Coefficient of coancestry (Θ = 0.208) showed that full-sibs constitute about 21% of the offspring in Kampi ya Moto population compared to about 14% (Θ = 0.136) in Lake Bogoria population. The results demonstrate that low adult tree density of A. senegal may be promoting seed production through consanguineous mating and suggest that man-made disturbance can affect mating patterns of the species. Despite these mating differences, trees from both populations can contribute as seed source for conservational plans, and to support effective genetic conservation and artificial regeneration programs of A. senegal. We suggest collection of seeds from at least 42 and 63 trees in Lake Bogoria and Kampi ya Moto populations, respectively, to retain a progeny array with a total effective population size of 150.     

Evaluation of resistance in different cowpea cultivars to Callosobruchus maculatus infestation

Cowpea [Vigna unguiculata (L.) Walp] seeds are an important source of nutrients for human and animal. However, part of the seed production is lost due to insect attacks, mainly by the weevil Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae), a major pest of stored cowpeas. An efficient method for controlling seed infestation is the use of insect-resistant cultivars. In this work, we studied the resistance of different cowpea Brazilian cultivars (BRS) to infestation and damage by C. maculatus. Our results showed that some cultivars interfered in female oviposition. The time necessary for the larvae to perforate the seed coat of some cultivars increased up to 40 %. No relationship between seed coat thickness, textures, or pigmentation and the larval ability of crossing seed coats was observed. Larval survival was also affected by cowpea cultivars. In BRS Xiquexique, only 30 % of the larvae survived at 20 days after oviposition. The weight of larvae developed into BRS Pajeu, and BRS Xiquexique cultivars decreased about 50 %. Cysteine protease, α-glucosidase, and α-amylase activities decreased in larvae developed in some cultivars, mainly in Pajeu, Guariba, Tucumaque, and Xiquexique. Adult emergence also decreased in Xiquexique, Pajeu, Tucumaque, and Paraguaçu BRS cultivars. A direct relationship between higher infestation and lower seed germination and seedling growth potential was observed. From these data, we would recommend the use of Pajeu, Guariba, Tucumaque, and Xiquexique BRS cultivars as a way to reduce cowpea infestation, and suggest that their resistance mechanism is related to the diminishment of larval digestive abilities.     

Pre-emergence herbicides affect seedling emergence of tropical forest tree species

Testing techniques to reduce weed infestation is a crucial step in developing direct tree seeding systems. The use of pre-emergence herbicides may be an alternative to manual weeding techniques, but so far, information on how they affect the seeds of native tree species is scarce. We established a greenhouse experiment to evaluate the effects of four pre-emergence herbicides (atrazine, diuron, isoxaflutole and oxyfluorfen) on weed suppression and seedling emergence and early growth of seven tropical forest tree species (Annona coriacea Mart., Citharexylum myrianthum Cham., Cordia ecalyculata Vell., Peltophorum dubium (Spreng.) Taub., Psidium guajava L., Pterogyne nitens Tul. and Schinus terebinthifolia Raddi). The experimental design was a randomized complete block design with five treatments and five replicates. The treatments consisted of a single dose of each pre-emergence herbicide and a control. Throughout the 60 days after sowing we evaluated weed cover and seedling emergence and early growth of tree species. Overall, our results suggest that all tested herbicides reduced weed cover; however, they also negatively affected tree species seedling emergence. Of the four herbicides tested, atrazine and diuron showed the greatest effects on tree seedling emergence, oxyfluorfen was least aggressive towards native species and isoxaflutole was most effective in weed control. Native tree species varied in their responses to herbicides, indicating that future experiments should increase the number of species tested as well as investigate how seed traits can affect the species responses to different herbicides.     

Provenance and pretreatment effect on seed germination of six provenances of <Emphasis Type="Italic">Faidherbia albida</Emphasis> (Delile) A. Chev

A nursery experiment was conducted to determine the effects of seed pretreatment methods on the germination of Faidherbia albida at ICRAF, Nairobi from six provenances consisting of Awassa, Taveta, Lake Koka, Maseno, Chinzombo and Wagingombe. Seeds were subjected to five pretreatment methods namely nicking, soaking in acid, hot water, cold water and control. Germination percentages (GP), mean germination time (MGT) and germination index (GI) were calculated and the data was subjected to ANOVA. The study revealed significant (p ≤ 0.05) differences in seed treatments among provenances in all studied parameters. Highest germination among pretreatments in Awassa (99 %) and Wagingombe (80 %) was observed in nicked seeds, Chinzombo (81 %) in nicked and acid treated seeds, Lake Koka (90 %) in acid treated seeds and Taveta (28 %) and Maseno (64 %) in cold water treated seeds. Nicking gave the highest cumulative GP (69.67) while lowest GP was observed in hot water treated seeds (23.17). Acid treatment exhibited lowest MGT (8.85 days) and highest GI (2.29) while highest MGT (24.35 days) and lowest GI (0.31) were observed in control and hot water treatment respectively. Although acid treatment gave a high GP and lowest MGT and GI, nicking and soaking in cold water for 24 h is being recommended as cheaper and less hazardous pretreatment methods to improve germination in F. albida since sulphuric acid is expensive and requires proper handling techniques. Significant correlation between geo-climatic data and germination parameters of seeds subjected to different pretreatments indicates that provenances are as important as pretreatments in germination of the species.     

In vitro germination and shoot proliferation of the threatened species <Emphasis Type="Italic">Cinchona officinalis</Emphasis> L (Rubiaceae).

Cinchona officinalis (Rubiaceae) is an endemic species of the Loja Valley in southern Ecuador with medicinal uses. Because of over-exploitation in the nineteenth century and more recent disturbances to its ecosystem, C. officinalis populations are threatened. Currently, natural regeneration of the populations is low, despite its high plant regeneration and seed formation capacity. In the present study, an efficient protocol for germination, shoot proliferation and plantlets regeneration was developed for this species. Phenolic content and germination rate of C. officinalis seeds were compared with a control species, C. pubescens. Nodal segments from seedlings of C. officinalis were cultured on Gamborg medium supplemented with different combinations of plant growth regulators. Because the phenol content is high in C. officinalis, the phenolic should be removed with hydrogen peroxide or water washes to stimulate germination. Shoots and callus developed from nodal segments within 45 days using most of the tested combinations of plant growth regulators. The best rates of shoot proliferation, callus formation and adventitious buds were obtained in medium supplemented with 5.0 mg L^?1 6-benzyl-aminopurine and 3.0 mg L^?1 indole-3-butyric acid.     

Optimal and synchronized germination of <Emphasis Type="Italic">Robinia pseudoacacia</Emphasis>, <Emphasis Type="Italic">Acacia dealbata</Emphasis> and other woody Fabaceae using a handheld rotary tool: concomitant reduction of physical and physiological seed dormancy

The Fabaceae (legume family) is one of the largest families of plants with a worldwide distribution and a major role in agriculture and in agroforestry. A hard seed coat impermeable to water is a typical feature of several species. Physical dormancy delays and reduces germination so that mechanical, physical and chemical scarification methods have been classically used to break seed dormancy of many species. We evaluate the effectiveness of a methodology to scarify seeds of several woody Fabaceae of ecological and economical importance, including Robinia pseudoacacia and Acacia dealbata and the shrubs Cytisus scoparius, C. multiflorus and Ulex europaeus. We describe the optimized use of a handheld rotary tool (HRT), and compare its effectiveness with other scarification methods reported to break dormancy such as boiling or dry heating. Total germination and/or speed of germination were enhanced after the application of the HRT, with germination percentages significantly higher than those achieved by other methods of scarification. Based on a thorough literature review, a mode of action for the HRT is suggested which could operate by breaking the physical and physiological dormancy of treated seeds through the combined action of coat abrasion and moderate temperatures. Considering these results, we recommend the application of this rapid, effective, low-cost and highly reproducible HRT method to break seed dormancy and enhance germination of these species and others with similar dormancy constraints.     

Pollen dispersal,mating patterns and pollen contamination in an insect-pollinated seed orchard of <Emphasis Type="Italic">Schima superba</Emphasis> Gardn. et Champ.

Pollen flow and mating patterns are the most important factors influencing the genetic structure of insect-pollinated forest trees and are essential parts of genetic management in seed orchards. We investigated pollen flow, the mating system and the level of pollen contamination in a clonal seed orchard of Schima superba Gardn. et Champ. In total, 328 open-pollination progenies coming from 11 mother trees were identified using 13 polymorphic microsatellite loci. A total of 203 full-sib families were identified and were nested among the 11 studied seed donors. The male reproductive success rate from 0.49 to 7.77% for most male parents, with an average of 2.44%. More than 80% of the crosses were found within a distance of 60 m, and the most frequent pollination distance between female parent and male parents was approximately 20 m. Mating system analysis showed that the outcrossing level was very high (t _m  = 1.000, outcrossing rate = 98.5%) in the seed orchard and that there was an average of 2.3 effective pollen donors (N _ep ) per female parent. In addition, the mating success of individual males within neighborhoods was moderately influenced by their fecundity and the direction of their location relative to mother trees. The pollen contamination from outside the seed orchard was high (7.01%). Our findings are valuable for the assessment of seed orchards, and it may be worthwhile to use pollen management strategies to decrease pollen contamination and increase the genetic quality of the seeds produced.     

Photosynthetic acclimation to long-term high temperature and soil drought stress in two spruce species (<Emphasis Type="Italic">Picea crassifolia</Emphasis> and <Emphasis Type="Italic">P. wilsonii</Emphasis>) used for afforestation

Picea crassifolia and P. wilsonii, commonly used for afforestation in northern China, are increasingly likely to be subjected to high temperatures and soil drought stress as a result of global warming. However, little is known about the effects of these stresses on foliar photosynthesis in the two species. To investigate how photosynthetic characteristics and sensitivity respond to prolonged high temperatures and soil drought, foliar gas exchange and other closely related parameters were recorded from four-year-old seedlings of both species. Seedlings were grown under two temperature treatments (25/15 and 35/25 °C) and four soil water regimes [80, 60, 40 and 20% of maximum field capacity (FC)] for 4 months. Although all treatments significantly reduced photosynthetic rates (P _n) of both species, P. crassifolia exhibited greater photosynthetic acclimation than P. wilsonii. Differences in photosynthetic acclimation were mainly related to variations in stomatal conductance (Cond) and the maximum quantum yield of PSII (F _v/F _m) between treatments. Indeed, higher Cond and F _v/F _m in all treatments were shown for P. crassifolia than for P. wilsonii. Moreover, photosynthesis in P. crassifolia exhibited inherently lower temperature sensitivities (broader span for the temperature response curves; lower b) and higher thermostability (invariable b between treatments). Further, severe drought stress (20% FC) limited the survival of P. wilsonii. Our results indicate that P. wilsonii is more susceptible to high temperatures and soil drought stress. Planting P. crassifolia would be more expected to survive these conditions and hence be of greater benefit to forest stability if predicted increases in drought and temperature in northern China occur.     

Identification of pests and assessment of their damage on <Emphasis Type="Italic">Carapa procera</Emphasis> and <Emphasis Type="Italic">Lophira lanceolata</Emphasis> in Burkina Faso,West Africa

Nontimber forest products are a source of income for women in rural African communities. However, these products are frequently damaged by insect pests. The present study investigates the diversity and damage rates of insect pests that attack Carapa procera seeds and Lophira lanceolata fruits. The experiment was set up in western Burkina Faso and, for C. carapa, consisted of pests collected from seeds that had fallen to the ground and from stockpiled seeds. For L. lanceolata, pests were collected from fruits on the trees, and on the ground. The collected samples were sent to the laboratory to estimate the proportion of damaged seeds/fruits and rear the insects. The results showed that Ephestia spp., Tribolium castaneum, Oryzeaphilus spp., and Tenebroides mauritanicus were the pests of Carapa procera seeds and Lophira lanceolata fruits. Ephestia spp. was recorded as the main pest of both C. procera and L. lanceolata, whereas T. castaneum was only detected from seeds of L. lanceolata. For C. procera, the stocks were the most infested (29 %) by Ephestia spp. The infestation rate of fruits of L. lanceolata by Ephestia spp. on trees (31.42 ± 3.75 %) was less than the rate of fruits by T. castaneum on the ground (44.00 ± 3.5 %). The different body sizes of Ephestia spp. may indicate the occurrence of two putative species, one from C. procera and another one from L. lanceolata. This work provides important information that could contribute to the setting up of a local-scale sustainable management framework for oil tree pests in Burkina Faso and surrounding countries.     

Upgrading germinability of ponderosa pine seeds from Patagonia,Argentina, by adjusting prechilling periods and applying the IDS technique

Ponderosa pine (Pinus ponderosa Dogl. ex. Laws.) is the most planted conifer species in the forest-steppe ecotone of Patagonia, Argentina, because of its adaptability and excellent growth rates. In spite of this, and the increasing demand for this species, local commercial seed lots showed low quality, making hazardous seedling production. Aiming to upgrade germinability of a local seed lot, we set an experiment to determine the duration of the prechilling period (0, 10, 20, 30, 40 and 60 days) that promoted the highest seed germination speed (GE) and percentage (GP). Moreover, part of that lot was IDS treated, in an attempt to separate empty and dead filled seeds from viable seeds. Results showed that after 40 days prechilling, GE reached 62%, and GP 70%, both higher than the values obtained under customary conditions. The application of the IDS technique, after 40 days prechilling, 8 h drying at ambient conditions (16 ± 2°C and 50% HR), and 25% seed moisture content (mc), increased GE and GP to 68% and 89%, respectively. Optimal prechilling periods and the application of the IDS technique successfully improved germinability of ponderosa pine seeds from Patagonian stands.     

Effects of acorn attack by curculio weevils on the germination and early growth of <Emphasis Type="Italic">Pasania edulis</Emphasis> (Makino) seedlings

We conducted field studies to evaluate the impact that curculio weevil attacks on Pasania edulis (Fagacea) acorns have on the regeneration of this tree. The germination ratio of weevil-attacked acorns was significantly lower than that of sound acorns. The number and position of the attacks on acorns affected the germination ratio. The seedlings from weevil-attacked acorns were shorter and had a smaller leaf area than those from sound acorns. The negative effects on seedling height lasted for at least three years after germination. We also studied the handling of the two types of acorns by granivorous Apodemus mice in a broad-leaved forest dominated by P. edulis. The mice picked up, transported, hoarded, and recovered sound and weevil-attacked acorns similarly. In the study site, the seedlings from weevil-attacked acorns were estimated to account for 1.5–20.4 % of the total seedlings for cohorts of mast years and 0–3.7 % for those of poor or medium acorn production. From these results, we conclude that acorns with the lower part of their cotyledons slightly damaged by weevil larvae might still be able to contribute to the regeneration of P. edulis in the field but that their contribution would be negligible or small even in mast years in this study site.     

Dry mass production,allocation patterns and water use efficiency of two conifers with different water use strategies under elevated [CO<Subscript>2</Subscript>], warming and drought conditions

Knowledge regarding the interactive effects of elevated [CO₂], warming and drought on dry mass production, allocation and water use efficiency (WUE) of tree seedlings is limited, particularly in trees exhibiting different stomatal regulation strategies. Seedlings of Callitris rhomboidea (relatively anisohydric) and Pinus radiata (relatively isohydric) were grown in two [CO₂] (C_a (400 μmol mol^?1) and C_e (640 μmol mol^?1)) and two temperature (T_a (ambient) and T_e (ambient?+?4 °C)) treatments in a sun-lit glasshouse under well-watered conditions prior to imposition of the drought. C_e increased mass production in C. rhomboidea (but not in P. radiata), while drought limited mass production in both species. Mass production was greatest in the combination of C_e, T_e and well-watered conditions. Pinus radiata allocated relatively more dry mass into roots and had higher plant WUE than C. rhomboidea. Noticeably, mass allocation patterns in C. rhomboidea varied as a function of the treatments, but those of P. radiata were constant. C_e enhanced leaf WUE of both species, but to a greater degree under drought stress than well-watered conditions. Moderate drought stress increased both leaf and plant WUE compared to well-watered conditions. C. rhomboidea exhibited plasticity to variable climate conditions through morphological adjustments, while P. radiata exhibited a highly conservative strategy. Collectively, these findings indicate that the two species have different strategies in resource acquisition and utilisation under changing environmental conditions. Future studies on tree response to climate change need to fully consider the integration of species traits, including stomatal behaviour and hydraulic strategies.     

Clonal variations in nutritional components of <Emphasis Type="Italic">Pinus koreansis</Emphasis> seeds collected from seed orchards in Northeastern China

From four Korean pine (Pinus koraiensis) orchards, 60 clones were selected and analyzed for the fatty acid and amino acid components of the seeds to reveal the variations and correlations of the seed characteristics among the clonal source orchards and clones. The nutritional components of the seeds of the P. koraiensis trees exhibited rich genetic variation; the variation coefficient of the fatty acids was 2.24–66.83 %, while the variation coefficient of the amino acids was 14.70–38.88 %. Relatively high genetic-improvement potential exists for the nutritional components of the seeds. The phenotypic differentiation of the fatty acid and amino acid components reveals that variation within the population (85.18 %) was the primary source for the variation of the fatty acid components; variation among the orchards (63.08 %) was the primary source of the variation of the amino acid components. Data drawn from various clonal source orchards all showed that the seed characteristics were highly controlled by heritability (h² > 80 %), and the seed characteristics of the P. koraiensis trees exhibited a similar genetic gain trend. The principal components were analyzed to obtain the comprehensive principal component value for each clonal seed orchard. Twelve clones were selected based on a clonal selection rate of 20 %. Correlation and multiple stepwise-regression analyses were conducted, considering different location conditions, to reveal the stable correlations between the seed characteristics to facilitate improvements of the seed yield of P. koraiensis trees and the clonal selection. Species of real characteristics in P. koraiensis were controlled by higher heritability. Genetic gain was obtained by selecting of superior clones.