Green fluorescent protein (GFP) fused to the F-actin binding domain of mouse talin labels the actin cytoskeleton in the living generative and sperm cells of a third generation transgenic rice (Oryza sativa L.) plant, ...Green fluorescent protein (GFP) fused to the F-actin binding domain of mouse talin labels the actin cytoskeleton in the living generative and sperm cells of a third generation transgenic rice (Oryza sativa L.) plant, A005-G-T-1-2. Observations were made on pollen at four major developmental stages, viz. I. uni-nucleate microspore stage; II. early bi-cellular pollen stage; III. late bi-cellular pollen stage; and IV. tri-cellular pollen stage. At each of these developmental stages vegetative nucleus, generative nucleus/ cell, and sperm cells were seen undergoing continuous and coordinated motion and migration. These movements seemed to be influenced by associated microfilament networks existing in the pollen. Based on these observations we propose that it is the interaction between the microfilament networks (usually one existing in the central cytoplasm and another in the cortex) that controls the dynamic movement of the vegetative nucleus, generative nucleus/cell and sperm cells. Furthermore, we have also observed that there is an array of microfilaments (oriented mostly parallel to the long axis of the cell) existing in the generative and sperm cells. As far as we are aware, this is the first report showing the existence of microfilaments in living generative and sperm cells of rice pollen. The implication and significance of the existence of microfilaments in generative and sperm cells in rendering self-propelled motion of these cells in relation to their passage and movement in the pollen tube and embryo sac for fertilization were discussed.展开更多
Green fluorescent protein (GFP) fused to the F_actin binding domain of mouse talin labels the actin cytoskeleton in the immature pollen of stable transformed rice (Oryza sativa L.) plants. Actin microfilaments could b...Green fluorescent protein (GFP) fused to the F_actin binding domain of mouse talin labels the actin cytoskeleton in the immature pollen of stable transformed rice (Oryza sativa L.) plants. Actin microfilaments could be visualized only in the late_developmental stage of the immature pollen. During this developmental stage, microfilaments, initially composed of very short fibrils, develop into a very complex and novel network that sometimes totally and sometimes partially encloses the vegetative nucleus and the spherical shaped generative cell in the central cytoplasm of the immature pollen. The behavior of the actin microfilamentous structure throughout the late_developmental stage of the immature pollen is extremely dynamic, and the likelihood of this structure in generating forces for vegetative nucleus and generative cell movement in the immature pollen has been discussed. No actin filaments were visualized in the spherical generative cells.展开更多
The need to maintain high rice yields and improve fertilizer nitrogen(N)-use efficiency has fueled the use of tools such as leaf colour chart(LCC) and chlorophyll meter(SPAD meter) in managing fertilizer N based on co...The need to maintain high rice yields and improve fertilizer nitrogen(N)-use efficiency has fueled the use of tools such as leaf colour chart(LCC) and chlorophyll meter(SPAD meter) in managing fertilizer N based on colour of the leaf. Field experiments were conducted during 2011 to 2013 at Ludhiana, India to assess the need for basal N application and to establish critical threshold values of leaf greenness as measured by LCC and SPAD meter for formulating strategies for in-season management of fertilizer N in dry direct-seeded rice(DDSR). Avoiding application of N at sowing did not adversely affect rice grain yield, indicating that basal N application in DDSR was not necessary and might lead to reduced N-use efficiency. Monitoring N uptake rate during the growing season of DDSR suggested that N uptake rate peaked at the two growth stages: maximum tillering(42 to 56 days after sowing(DAS))and panicle initiation stages(70 to 84 DAS). Using the Cate-Nelson procedure, critical LCC and SPAD meter values for fertilizer N application worked out to be 4 and 37, respectively. Real-time fertilizer N management strategy based on applying 30 kg N ha-1whenever SPAD meter or LCC readings fell below the critical values maintained optimum rice yields along with higher N-use efficiency than that observed by following blanket recommendation for fertilizer N in the region. The fixed-time variable-dose strategy consisted of applying prescriptive doses of 20 kg N ha-1at 14 DAS and 30 kg N ha-1at 28 DAS and corrective doses of 30, 40 or 50 kg N ha-1at 49 and 70 DAS depending upon LCC shade to be ≥ 4, 4–3.5, or < 3.5 and SPAD meter readings to be ≥ 40, 40–35, or< 35, respectively. This strategy also resulted in optimal rice yield along with higher N-use efficiency as compared to the blanket recommendation. This study revealed that in DDSR, fertilizer N could be managed more efficiently using the tools of LCC and SPAD meter than the current blanket recommendation.展开更多
文摘Green fluorescent protein (GFP) fused to the F-actin binding domain of mouse talin labels the actin cytoskeleton in the living generative and sperm cells of a third generation transgenic rice (Oryza sativa L.) plant, A005-G-T-1-2. Observations were made on pollen at four major developmental stages, viz. I. uni-nucleate microspore stage; II. early bi-cellular pollen stage; III. late bi-cellular pollen stage; and IV. tri-cellular pollen stage. At each of these developmental stages vegetative nucleus, generative nucleus/ cell, and sperm cells were seen undergoing continuous and coordinated motion and migration. These movements seemed to be influenced by associated microfilament networks existing in the pollen. Based on these observations we propose that it is the interaction between the microfilament networks (usually one existing in the central cytoplasm and another in the cortex) that controls the dynamic movement of the vegetative nucleus, generative nucleus/cell and sperm cells. Furthermore, we have also observed that there is an array of microfilaments (oriented mostly parallel to the long axis of the cell) existing in the generative and sperm cells. As far as we are aware, this is the first report showing the existence of microfilaments in living generative and sperm cells of rice pollen. The implication and significance of the existence of microfilaments in generative and sperm cells in rendering self-propelled motion of these cells in relation to their passage and movement in the pollen tube and embryo sac for fertilization were discussed.
文摘Green fluorescent protein (GFP) fused to the F_actin binding domain of mouse talin labels the actin cytoskeleton in the immature pollen of stable transformed rice (Oryza sativa L.) plants. Actin microfilaments could be visualized only in the late_developmental stage of the immature pollen. During this developmental stage, microfilaments, initially composed of very short fibrils, develop into a very complex and novel network that sometimes totally and sometimes partially encloses the vegetative nucleus and the spherical shaped generative cell in the central cytoplasm of the immature pollen. The behavior of the actin microfilamentous structure throughout the late_developmental stage of the immature pollen is extremely dynamic, and the likelihood of this structure in generating forces for vegetative nucleus and generative cell movement in the immature pollen has been discussed. No actin filaments were visualized in the spherical generative cells.
基金supported by the Indian Council of Cultural Relations and Egypt Government through the Cultural Exchange Programme
文摘The need to maintain high rice yields and improve fertilizer nitrogen(N)-use efficiency has fueled the use of tools such as leaf colour chart(LCC) and chlorophyll meter(SPAD meter) in managing fertilizer N based on colour of the leaf. Field experiments were conducted during 2011 to 2013 at Ludhiana, India to assess the need for basal N application and to establish critical threshold values of leaf greenness as measured by LCC and SPAD meter for formulating strategies for in-season management of fertilizer N in dry direct-seeded rice(DDSR). Avoiding application of N at sowing did not adversely affect rice grain yield, indicating that basal N application in DDSR was not necessary and might lead to reduced N-use efficiency. Monitoring N uptake rate during the growing season of DDSR suggested that N uptake rate peaked at the two growth stages: maximum tillering(42 to 56 days after sowing(DAS))and panicle initiation stages(70 to 84 DAS). Using the Cate-Nelson procedure, critical LCC and SPAD meter values for fertilizer N application worked out to be 4 and 37, respectively. Real-time fertilizer N management strategy based on applying 30 kg N ha-1whenever SPAD meter or LCC readings fell below the critical values maintained optimum rice yields along with higher N-use efficiency than that observed by following blanket recommendation for fertilizer N in the region. The fixed-time variable-dose strategy consisted of applying prescriptive doses of 20 kg N ha-1at 14 DAS and 30 kg N ha-1at 28 DAS and corrective doses of 30, 40 or 50 kg N ha-1at 49 and 70 DAS depending upon LCC shade to be ≥ 4, 4–3.5, or < 3.5 and SPAD meter readings to be ≥ 40, 40–35, or< 35, respectively. This strategy also resulted in optimal rice yield along with higher N-use efficiency as compared to the blanket recommendation. This study revealed that in DDSR, fertilizer N could be managed more efficiently using the tools of LCC and SPAD meter than the current blanket recommendation.
