• Energy Research

Dioecious plants, which comprise more than 14,620 species, account for an important component of terrestrial ecosystems. Hence, understanding the sexually dimorphic responses in balancing carbon (C) supply and demand under elevated CO(2) is important for understanding leaf sink-to-source transitions. Here we investigate sex-related responses of the dioecious Populus cathayana Rehd. to elevated CO(2) and elevated temperature. The plants were grown in environmentally controlled growth chambers at two CO(2) enrichment regimes (350 ± 20 and 700 ± 20 μmol mol(-1)) with two temperature levels, elevated by 0 and 2 ± 0.2 °C (compared with the out-of-chamber environment). Plant growth characteristics, carbohydrate accumulation, C and nitrogen (N) allocation, photosynthetic capacity, N use efficiency and the morphology of mesophyll cells were investigated in the developing leaves (DLs) and expanded leaves (ELs) of both males and females. Elevated CO(2) enhanced plant growth and photosynthetic capacity in DLs of both males and females, and induced the male ELs to have a greater leaf mass production, net photosynthesis rate (P(n)), chlorophyll a/b ratio (Chl a/b), soluble protein level (SP), photosynthetic N use efficiency and soluble sugar level compared with females at the same leaf stage. Elevated temperature enhanced source activities and N uptake status during CO(2) enrichment, and the combined treatment induced males to be more responsive than females in sink capacities, especially in ELs, probably due to greater N acquisition from other plant parts. Our findings showed that elevated CO(2) increases the sink capacities of P. cathayana seedlings, and elevated temperature enhances the stimulation effect of elevated CO(2) on plant growth. Male ELs were found to play an important role in N acquisition from roots and stems under decreasing N in total leaves under elevated CO(2). Knowledge of the sex-specific leaf adaptability to warming climate can help us to understand sex-related source-to-sink transitions in dioecious plant species.

Dioecious plants, which comprise more than 14,620 species, account for an important component of terrestrial ecosystems. Hence, understanding the sexually dimorphic responses in balancing carbon (C) supply and demand under elevated CO(2) is important for understanding leaf sink-to-source transitions. Here we investigate sex-related responses of the dioecious Populus cathayana Rehd. to elevated CO(2) and elevated temperature. The plants were grown in environmentally controlled growth chambers at two CO(2) enrichment regimes (350 ± 20 and 700 ± 20 μmol mol(-1)) with two temperature levels, elevated by 0 and 2 ± 0.2 °C (compared with the out-of-chamber environment). Plant growth characteristics, carbohydrate accumulation, C and nitrogen (N) allocation, photosynthetic capacity, N use efficiency and the morphology of mesophyll cells were investigated in the developing leaves (DLs) and expanded leaves (ELs) of both males and females. Elevated CO(2) enhanced plant growth and photosynthetic capacity in DLs of both males and females, and induced the male ELs to have a greater leaf mass production, net photosynthesis rate (P(n)), chlorophyll a/b ratio (Chl a/b), soluble protein level (SP), photosynthetic N use efficiency and soluble sugar level compared with females at the same leaf stage. Elevated temperature enhanced source activities and N uptake status during CO(2) enrichment, and the combined treatment induced males to be more responsive than females in sink capacities, especially in ELs, probably due to greater N acquisition from other plant parts. Our findings showed that elevated CO(2) increases the sink capacities of P. cathayana seedlings, and elevated temperature enhances the stimulation effect of elevated CO(2) on plant growth. Male ELs were found to play an important role in N acquisition from roots and stems under decreasing N in total leaves under elevated CO(2). Knowledge of the sex-specific leaf adaptability to warming climate can help us to understand sex-related source-to-sink transitions in dioecious plant species.

Nitrogen (N) deposition affects plant growth and interspecific interaction. This study aimed to explore the effect of N deposition on the growth and eco-physiological interactions between two tree species dominating in subtropical forests. A greenhouse experiment was conducted for 6 months in which the conifer Cunninghamia lanceolata and the broadleaved Phoebe chekiangensis were grown in monocultures and in a mixture under two levels of N addition: 0 and 45 kg ha-1 yr-1. The plant growth, root architecture, biomass distribution, element contents in plants and soil, and photosynthetic physiology were determined. The height and crown width of both seedlings tended to be higher in the mixture than in the monoculture when grown without N addition. P. chekiangensis was superior to C. lanceolata in resource acquisition and showed a greater net photosynthetic rate, plant height, crown width, total biomass, and belowground biomass distribution. In the mixture, N addition increased the net photosynthetic rate and decreased the height, ground diameter, and crown width of both species. Belowground biomass distribution was decreased in C. lanceolata but increased in P. chekiangensis under N addition. The P contents in both seedlings were higher in the mixture than in monocultures. Results showed N addition aggravated the competition and weakened the growth of both species in the mixture, largely determined by the competition for resources through the changing root architecture and biomass allocation. Our results provide new insights into the mechanisms of interspecific interaction in response to increasing N deposition in silvicultural practice.

Nitrogen (N) deposition affects plant growth and interspecific interaction. This study aimed to explore the effect of N deposition on the growth and eco-physiological interactions between two tree species dominating in subtropical forests. A greenhouse experiment was conducted for 6 months in which the conifer Cunninghamia lanceolata and the broadleaved Phoebe chekiangensis were grown in monocultures and in a mixture under two levels of N addition: 0 and 45 kg ha-1 yr-1. The plant growth, root architecture, biomass distribution, element contents in plants and soil, and photosynthetic physiology were determined. The height and crown width of both seedlings tended to be higher in the mixture than in the monoculture when grown without N addition. P. chekiangensis was superior to C. lanceolata in resource acquisition and showed a greater net photosynthetic rate, plant height, crown width, total biomass, and belowground biomass distribution. In the mixture, N addition increased the net photosynthetic rate and decreased the height, ground diameter, and crown width of both species. Belowground biomass distribution was decreased in C. lanceolata but increased in P. chekiangensis under N addition. The P contents in both seedlings were higher in the mixture than in monocultures. Results showed N addition aggravated the competition and weakened the growth of both species in the mixture, largely determined by the competition for resources through the changing root architecture and biomass allocation. Our results provide new insights into the mechanisms of interspecific interaction in response to increasing N deposition in silvicultural practice.

Abstract Dioecious trees have evolved sex-specific adaptation strategies to cope with inorganic phosphorus (Pi) limitation. Yet, little is known about the effects of Pi limitation on plant metabolism, particularly in dioecious woody plants. To identify potential gender-specific metabolites appearing in response to Pi limitation in poplars, we studied the metabolic and ionomic responses in the roots and leaves of Populus cathayana Rehd males and females exposed to a 60-day period of Pi deficiency. Besides significant decreases in phosphorus contents in both Pi-deficient roots and leaves, the calcium level decreased significantly and the sulfur content increased significantly in Pi-deficient male roots, while the zinc and ferrum contents increased significantly in Pi-deficient female roots. Inorganic P deficiency caused a smaller change in the abscisic acid content, but a significant increase in the jasmonic acid content was detected in both leaves and roots. Salicylic acid significantly decreased under Pi deficiency in male leaves and female roots. Changes were found in phospholipids and phosphorylated metabolites (e.g., fructose-6-phosphate, glycerol-3-phosphate, glucose-6-phosphate, phosphoric acid and inositol-1-phosphate) in roots and leaves. Both P. cathayana males and females relied on inorganic pyrophosphate-dependent but not on Pi-dependent glycolysis under Pi-deficient conditions. Sex-specific metabolites in leaves were primarily in the category of primary metabolites (e.g., amino acids), while in roots primarily in the category of secondary metabolites (e.g., organic acids) and sugars. The metabolome analysis revealed that sexually different pathways occurred mainly in amino acid metabolism, and the tissue-related differences were in the shikimate pathway and glycolysis. We observed changes in carbon flow, reduced root biomass and increased amino acid contents in P. cathayana males but not in females, which indicated that males have adopted an energy-saving strategy to adapt to Pi deficiency. Thus, this study provides new insights into sex-specific metabolic responses to Pi deficiency.

Abstract Dioecious trees have evolved sex-specific adaptation strategies to cope with inorganic phosphorus (Pi) limitation. Yet, little is known about the effects of Pi limitation on plant metabolism, particularly in dioecious woody plants. To identify potential gender-specific metabolites appearing in response to Pi limitation in poplars, we studied the metabolic and ionomic responses in the roots and leaves of Populus cathayana Rehd males and females exposed to a 60-day period of Pi deficiency. Besides significant decreases in phosphorus contents in both Pi-deficient roots and leaves, the calcium level decreased significantly and the sulfur content increased significantly in Pi-deficient male roots, while the zinc and ferrum contents increased significantly in Pi-deficient female roots. Inorganic P deficiency caused a smaller change in the abscisic acid content, but a significant increase in the jasmonic acid content was detected in both leaves and roots. Salicylic acid significantly decreased under Pi deficiency in male leaves and female roots. Changes were found in phospholipids and phosphorylated metabolites (e.g., fructose-6-phosphate, glycerol-3-phosphate, glucose-6-phosphate, phosphoric acid and inositol-1-phosphate) in roots and leaves. Both P. cathayana males and females relied on inorganic pyrophosphate-dependent but not on Pi-dependent glycolysis under Pi-deficient conditions. Sex-specific metabolites in leaves were primarily in the category of primary metabolites (e.g., amino acids), while in roots primarily in the category of secondary metabolites (e.g., organic acids) and sugars. The metabolome analysis revealed that sexually different pathways occurred mainly in amino acid metabolism, and the tissue-related differences were in the shikimate pathway and glycolysis. We observed changes in carbon flow, reduced root biomass and increased amino acid contents in P. cathayana males but not in females, which indicated that males have adopted an energy-saving strategy to adapt to Pi deficiency. Thus, this study provides new insights into sex-specific metabolic responses to Pi deficiency.

ABSTRACTDrought stress responses and sensitivity of dioecious plants, such as Populus cathayana Rehd., are determined by different mechanisms in each sex. In general, males tend to be more resistant while females are more sensitive. Here, we used reciprocal grafting between males and females to determine the relative importance of roots and shoots when plants are exposed to drought stress. Total dry matter accumulation (DMA), photosynthetic capacity, long‐term water‐use efficiency (Δ), water potential and ultrastructure of mesophyll cells were evaluated to determine the different roles of root and shoot in sex‐related drought responses. Plants with male roots were found to be more resistant and less sensitive to water stress than those with female roots under drought conditions. On the contrary, plants with female shoots grew better than those with male shoots under well‐watered conditions. These results indicated that the sensitivity of males and females to water stress is primarily influenced by root processes, while under well‐watered conditions sexual differences in growth are primarily driven by shoot processes. Furthermore, grafting female shoot scion onto male rootstock was proved to be an effective mean to improve resistance to water stress in P. cathayana females.

ABSTRACTDrought stress responses and sensitivity of dioecious plants, such as Populus cathayana Rehd., are determined by different mechanisms in each sex. In general, males tend to be more resistant while females are more sensitive. Here, we used reciprocal grafting between males and females to determine the relative importance of roots and shoots when plants are exposed to drought stress. Total dry matter accumulation (DMA), photosynthetic capacity, long‐term water‐use efficiency (Δ), water potential and ultrastructure of mesophyll cells were evaluated to determine the different roles of root and shoot in sex‐related drought responses. Plants with male roots were found to be more resistant and less sensitive to water stress than those with female roots under drought conditions. On the contrary, plants with female shoots grew better than those with male shoots under well‐watered conditions. These results indicated that the sensitivity of males and females to water stress is primarily influenced by root processes, while under well‐watered conditions sexual differences in growth are primarily driven by shoot processes. Furthermore, grafting female shoot scion onto male rootstock was proved to be an effective mean to improve resistance to water stress in P. cathayana females.