Elevated CO2 during pod filling increased seed yield but not harvest index in indeterminate narrow-leafed lupin

Abstract

Indeterminate narrow-leafed lupin (Lupinus angustifolius L. cv. Merrit) was exposed to enriched atmospheric CO2 during pod-filling to enhance the availability of carbon resources for pod-filling in order to determine whether or not seed-filling, yield, and harvest index are limited by the availability of photosynthetic assimilate. Plants were grown in a glasshouse and the flowers painted with an aqueous solution containing either N6-benzylaminopurine (BAP) or no BAP to generate 2 different numbers of pods per plant. From the time when pods began to fill seeds (≥5 mg/seed) until maturity, plants were exposed to either ambient (350–360 L/L) or enriched (700 L/L) CO2 by enclosing them in 2 transparent, box-shaped tunnels with similar temperatures, light, and water conditions. Whether or not BAP was applied to flowers, CO2 enrichment increased the final number of pods and the number of pods that filled large seeds (≥150 mg) by 20–22 pods/plant. Enriched CO2 reduced to zero the number of pods that had small seeds (≥30–80 mg) and reduced the number of pods with unfilled seeds from 16 to 1 pod/plant. This increased seed yield per plant by 44–66%, but did not affect the harvest index. Harvest index was unchanged because enriched CO2, while increasing pod-filling, also increased pod set and dry matter accumulation on the developing branches. This indicates that an increased availability of carbon resources during-pod filling changed the allocation of assimilates by filling small seeds and producing new branches. The 47–56% increase in dry matter per plant was reflected in the increase in seed yield, which occurred largely through an increased number of pods and seeds per plant. These data support the idea that seed-filling and hence seed yield in well-nodulated, indeterminate narrow-leafed lupin is limited by carbon resources at the stage when the plant is most source-limited, which is during podset and pod-filling.

Foliar nitrogen applications increase the seed yield and protein content in chickpea (Cicer arietinum L.) subject to terminal drought

“…A decline in leaf photosynthesis is symptomatic of leaf senescence (Thomas and Stoddart 1980;Egli and Crafts-Brander 1996) and leaf senescence is accelerated by moisture stress (de Souza et al 1997). It is likely, however, that the 20% increase in biomass resulting from foliar applications of urea at the first flower and 50% flowering, increased total canopy photosynthesis (Charles-Edwards et al 1986), consistent with the findings of Egli and Yu (1991) that seeds per pod in soybean are a function of canopy photosynthesis during flowering and pod set, and with the results of Palta and Ludwig (2000) that an increase in the availability of carbon resources before terminal drought develops increased seed set and seed survival.…”

“…It is assumed that in this study, nitrogen fixation was reduced because the source of carbon that is critical for the survival of the Rhizobia bacteria and continuation of nitrogen fixation (Pate and Herridge 1978) was reduced by the water deficit (Hooda et al 1989). It is also likely that after flowering, carbon was preferentially allocated to the developing pods (Palta and Ludwig 2000), which made the nitrogen fixed prior to podding more critical for seed filling. This was apparent since the nitrogen derived from the foliar application of urea at the first flower and 50% flowering did not account for the total increase in nitrogen that resulted from each application, indicating that nitrogen fixation was enhanced.…”

Variability in Phenology, Physiology and Yield Response of Different Maturity Duration Pigeon Pea Genotypes at Elevated CO2

“…This high biomass and high seed yield short-medium duration genotype response was found to be different from the extra-short and short duration genotypes in proportioning the extra biomass accumulated due to elevated CO 2 . Similar increase of dry matter (52%) and seed yield (55%) was recorded in narrowleafed lupin with elevated CO 2 (Palta and Ludwig, 2000) Climate Change and Environmental Sustainability (October 2015) 3(2): 131-136 and in soybean cultivars (Hao et al, 2012). Pigeon pea-a C 3 crop registered improved physiological, biomass and seed yield parameters with elevated CO 2 and the magnitude of the response differed with genotype.…”

Elevated CO2 Reduced Floret Death in Wheat Under Warmer Average Temperatures and Terminal Drought

“…The carbon resources needed to produce florets are insignificant compared to that needed to support floret growth and development ( Kirby, 1988 ; Ferrante et al, 2013a ). Therefore, the high rates of net leaf photosynthesis under elevated CO 2 most likely provided sufficient carbon assimilates ( Balaguer et al, 1995 ; Palta and Ludwig, 2000 ) that enabled greater survival of competent florets. Greater availability of carbon assimilates have previously been suggested as the cause of floret mortality reduction ( Siddique et al, 1989 ; Miralles et al, 1998 ).…”