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Physiological Correlates of Variation in Nitrogen‐Use Efficiency in Two Contrasting Sugarcane Cultivars
Author(s) -
Ranjith Subasinghe A.,
Meinzer Frederick C.
Publication year - 1997
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1997.0011183x003700030021x
Subject(s) - biology , photosynthesis , dry matter , rubisco , saccharum , cultivar , agronomy , biomass partitioning , stomatal conductance , salinity , chlorophyll , photosynthetic capacity , water use efficiency , transpiration , nitrogen , dry weight , horticulture , botany , biomass (ecology) , chemistry , ecology , organic chemistry
The efficiency of N utilization in photosynthesis and dry matter production (NUE) is an important crop performance criterion. Our objectives were to characterize the magnitude and physiological correlates of variation in NUE in the C 4 grass, sugarcane ( Saccharum spp. hybrid). Two genotypes known to differ with regard to their resistance to drought and salinity stress were grown in solution culture in a glasshouse at three levels of N availability (0.1, 1.0, and 10 m M N). Photosynthetic gas exchange, dry matter accumulation, carboxylase activity, chlorophyll content, leaf N status, and plant‐water relations characteristics were evaluated. Leaf water potential and plant hydraulic conductance decreased as applied N was reduced from 10 to 0.1 m M . At a given leaf N status, NUE was always significantly higher in the stress‐resistant genotype (H69‐8235) than in the susceptible genotype (H65‐7052). However, a large genetic difference in dry weight accumulation at a given level of external N supply was observed only at 10 m M applied N. Higher NUE in H69‐8235 was strongly associated with greater relative partitioning of leaf N to chlorophyll and ribulose 1,5‐bisphosphate carboxylase‐oxygenase (Rubisco). The fraction of leaf N partitioned to the photosynthetic apparatus increased with declining N content in both genotypes. Photosynthetic and dry matter‐based NUE were not entirely consistent with each other because growth was more sensitive than photosynthesis to N stress. It may be possible to further improve the already high NUE of C 4 grasses by screening genotypes for differences in partitioning of leaf N into components of the photosynthetic apparatus such as chlorophyll and Rubisco.