Hevea brasiliensis is a commercially cultivated species for its natural rubber（NR） latex in South East Asian countries. To meet the ever-increasing demand, NR cultivation has been extended to non-traditional regions...Hevea brasiliensis is a commercially cultivated species for its natural rubber（NR） latex in South East Asian countries. To meet the ever-increasing demand, NR cultivation has been extended to non-traditional regions due to the limited scope of further expansion in traditional rubbergrowing areas in India. These areas are often confronted with various abiotic stresses, especially high and low temperatures, which cause reduction in plant growth, thereby increasing its uneconomical immaturity period. Eighteen wild Hevea accessions along with two modern clones RRII203 and PB 235 and two check clones RRIM 600 and Haiken 1 were evaluated in the early mature growth phase.The site was at Nagrakata, West Bengal, the sub-Himalayan cold-prone region of India. In Hevea, crop production is governed by two major factors, growth-vigor and production capacity. Growth-vigor is of special importance because the production of rubber is a process linked with the early growth of the plant, which results in early tappability and early economic gains. The genotypes exhibited highly significant clonal differences（P = 0.05） for all the growth traits. Tappability percentage in the seventh year, ranged from 0.33 %（AC 3074, AC 3075, AC 3293） to 89.67 %（RO 2727）. The most vigorously growing accession（RO2727） reached tappabile girth early in the seventh year when the girth of plant ranged from 22.38 cm（AC 3293） to53.12 cm（RO 2727）. The general mean was 43.32 cm, and the similar growth trend was exhibited by these accessions in the tenth year also. Annual girth increment（cm a-1） over3 years ranged from 1.81 cm（AC 3075） to 6.80 cm（RO2727）. The mean winter girth increment（cm a-1） over4 years ranged from 0.13 cm（AC 3075） to 0.96 cm（RO2727） as compared to the check clone RRIM 600（1.11 cm）and Haiken 1（1.10 cm）. Wide differences between the phenotypic coefficient of variation（50.29） and genotypic coefficient of variation（24.82） were observed for winter girth increment. Girth in the tenth year recorded the highest heritability（87 %）. Girth was significantly correlated with the other growth traits. The top 30 % of the potential accessions showing high growth vigour and early tappability under cold stress were identified. These ecotypes/selections have high potential value for the development of coldtolerant clones for these regions and also in broadening the genetic base of the present-day cultivated rubber.展开更多
The human central nervous system（CNS）has a markedly poor capacity for regenerating its axons following injury.This appears to be due to two main causes：1）a developmentally regulated decline in regenerative capacit...The human central nervous system（CNS）has a markedly poor capacity for regenerating its axons following injury.This appears to be due to two main causes：1）a developmentally regulated decline in regenerative capacity within mature CNS neurons,and 2）the presence of biological components that constitute barriers to axon regeneration（e.g.,growth-inhibitory molecules）.展开更多
文摘Hevea brasiliensis is a commercially cultivated species for its natural rubber（NR） latex in South East Asian countries. To meet the ever-increasing demand, NR cultivation has been extended to non-traditional regions due to the limited scope of further expansion in traditional rubbergrowing areas in India. These areas are often confronted with various abiotic stresses, especially high and low temperatures, which cause reduction in plant growth, thereby increasing its uneconomical immaturity period. Eighteen wild Hevea accessions along with two modern clones RRII203 and PB 235 and two check clones RRIM 600 and Haiken 1 were evaluated in the early mature growth phase.The site was at Nagrakata, West Bengal, the sub-Himalayan cold-prone region of India. In Hevea, crop production is governed by two major factors, growth-vigor and production capacity. Growth-vigor is of special importance because the production of rubber is a process linked with the early growth of the plant, which results in early tappability and early economic gains. The genotypes exhibited highly significant clonal differences（P = 0.05） for all the growth traits. Tappability percentage in the seventh year, ranged from 0.33 %（AC 3074, AC 3075, AC 3293） to 89.67 %（RO 2727）. The most vigorously growing accession（RO2727） reached tappabile girth early in the seventh year when the girth of plant ranged from 22.38 cm（AC 3293） to53.12 cm（RO 2727）. The general mean was 43.32 cm, and the similar growth trend was exhibited by these accessions in the tenth year also. Annual girth increment（cm a-1） over3 years ranged from 1.81 cm（AC 3075） to 6.80 cm（RO2727）. The mean winter girth increment（cm a-1） over4 years ranged from 0.13 cm（AC 3075） to 0.96 cm（RO2727） as compared to the check clone RRIM 600（1.11 cm）and Haiken 1（1.10 cm）. Wide differences between the phenotypic coefficient of variation（50.29） and genotypic coefficient of variation（24.82） were observed for winter girth increment. Girth in the tenth year recorded the highest heritability（87 %）. Girth was significantly correlated with the other growth traits. The top 30 % of the potential accessions showing high growth vigour and early tappability under cold stress were identified. These ecotypes/selections have high potential value for the development of coldtolerant clones for these regions and also in broadening the genetic base of the present-day cultivated rubber.
文摘The human central nervous system（CNS）has a markedly poor capacity for regenerating its axons following injury.This appears to be due to two main causes：1）a developmentally regulated decline in regenerative capacity within mature CNS neurons,and 2）the presence of biological components that constitute barriers to axon regeneration（e.g.,growth-inhibitory molecules）.
