Abstract
Fertilizer N availability impacts photosynthesis and crop performance, although cause–effect relationships are not well established, especially for field-grown plants. Our objective was to determine the relationship between N supply and photosynthetic capacity estimated by leaf area index (LAI) and single leaf photosynthesis using genetically diverse field-grown maize ( Zea mays L.) hybrids. We compared a high yield potential commercial hybrid (FR1064 x LH185) and an experimental hybrid (FR1064 x IHP) with low yield potential but exceptionally high grain protein concentration. Plant biomass and physiological traits were measured at tassel emergence (VT) and at the grain milk stage (R3) to assess the effects of N supply on photosynthetic source capacity and N uptake, and grain yield and grain N were measured at maturity. Grain yield of FR1064 x LH185 was much greater than FR1064 x IHP even though plant biomass and LAI were larger for FR1064 x IHP, and single leaf photosynthesis was similar for both hybrids. Although photosynthetic capacity was not related to hybrid differences in productivity, increasing N supply led to proportional increases in grain yield, plant biomass, LAI, photosynthesis, and Rubisco and PEP carboxylase activities for both hybrids. Thus, a positive relationship between photosynthetic capacity and yield was revealed by hybrid response to N supply, and the relationship was similar for hybrids with a marked difference in yield potential. For both hybrids the N response of single leaf CER and initial Rubisco activity was negative when expressed per unit of leaf N. In contrast, PEP carboxylase activity per unit leaf N increased in response to N availability, indicating that PEP carboxylase served as a reservoir for excess N accumulation in field-grown maize leaves. The correlation between CER and initial Rubisco activity was highly significant when expressed on a leaf area or a total leaf basis. The results suggest that regardless of genotypic yield potential, maize CER, and potentially grain yield, could be improved by increasing the partitioning of N into Rubisco.
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Claims 12
Claim · model-written summary
FR1064 x LH185 yielded much more grain than FR1064 x IHP.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Grain yield of FR1064 x LH185 was much greater than FR1064 x IHP”
t0“maize hybrids”
Claim · model-written summary
FR1064 x IHP had greater biomass and LAI than FR1064 x LH185.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“plant biomass and LAI were larger for FR1064 x IHP”
t0“maize hybrids”
Claim · model-written summary
Single leaf photosynthesis was similar between the two maize hybrids.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“single leaf photosynthesis was similar for both hybrids”
t0“maize hybrids”
Claim · model-written summary
Increasing nitrogen raised maize grain yield and biomass proportionally for both hybrids.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increasing N supply led to proportional increases in grain yield, plant biomass, LAI, photosynthesis, and Rubisco and PEP carboxylase activities for both hybrids”
t0“maize hybrids”
Claim · model-written summary
Increasing nitrogen raised maize LAI and photosynthesis proportionally for both hybrids.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increasing N supply led to proportional increases in grain yield, plant biomass, LAI, photosynthesis, and Rubisco and PEP carboxylase activities for both hybrids”
t0“maize hybrids”
Claim · model-written summary
Increasing nitrogen raised Rubisco and PEP carboxylase activities proportionally for both maize hybrids.
- Treatment
- increasing N supplye0
- Gene
- Rubisco and PEP carboxylasee0
- Outcome
- Rubisco and PEP carboxylase activitiese0
- Direction
- increasese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increasing N supply led to proportional increases in grain yield, plant biomass, LAI, photosynthesis, and Rubisco and PEP carboxylase activities for both hybrids”
t0“maize hybrids”
Claim · model-written summary
Photosynthetic capacity and yield were positively related across maize nitrogen responses, similarly in both hybrids.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a positive relationship between photosynthetic capacity and yield was revealed by hybrid response to N supply, and the relationship was similar for hybrids with a marked difference in yield potential”
t0“maize hybrids”
Claim · model-written summary
Higher nitrogen reduced single leaf CER per unit leaf nitrogen in both maize hybrids.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For both hybrids the N response of single leaf CER and initial Rubisco activity was negative when expressed per unit of leaf N”
t0“maize hybrids”
Claim · model-written summary
Higher nitrogen reduced initial Rubisco activity per unit leaf nitrogen in both maize hybrids.
- Treatment
- Ne0
- Gene
- Rubiscoe0
- Outcome
- initial Rubisco activitye0
- Direction
- negativee0
- Qualifier
- per unit of leaf Ne0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For both hybrids the N response of single leaf CER and initial Rubisco activity was negative when expressed per unit of leaf N”
t0“maize hybrids”
Claim · model-written summary
PEP carboxylase activity per unit leaf nitrogen increased with nitrogen availability.
- Treatment
- N availabilitye0
- Gene
- PEP carboxylasee0
- Outcome
- PEP carboxylase activity per unit leaf Ne0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“PEP carboxylase activity per unit leaf N increased in response to N availability”
t0“maize hybrids”
Claim · model-written summary
CER correlated significantly with initial Rubisco activity on leaf-area and total-leaf bases.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The correlation between CER and initial Rubisco activity was highly significant when expressed on a leaf area or a total leaf basis”
t0“maize hybrids”
Claim · model-written summary
Authors suggest partitioning more nitrogen into Rubisco could improve maize CER and perhaps yield.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maize CER, and potentially grain yield, could be improved by increasing the partitioning of N into Rubisco”
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