Spikelet Abortion Research Articles

Kernel Set and Flower Synchrony within the Ear of Maize : II. Plant Population Effects

Kernel number (KN) per plant declines with increasing plant population (PP) in maize (Zea mays L.) and controversy exists about the critical period for spikelet abortion. In this work, the effect of PP (5 and 9 plants m−2) on floral differentiation and kernel set was analyzed for two genotypes of contrasting prolificacy at Grignon, France, (48°51′N). Kernel set variability was tested at Balcarce (37°45′S), Argentina, with three PP (2, 8, and 16 plants m−2) and athinning treatment (from 16 to 2 plants m−2) at silking. Plants were grown with no water or nutrient restrictions. At 9 plants m−2, floral differentiation was delayed in apical ears but almost all spikelets started silk elongation. In subapical ears, 17% of the spikelets of the nonprolific hybrid and 19% of the prolific hybrid had not completed development at silking. At 5 plants m−2 these proportions were reduced to 6%. Significant (P < 0.01) differences were detected in apical ear length after the onset of rapid ear growth (silking −20 d), resulting in reduced ear biomass at silking at high PP. Barrenness occurred at 16 plants m−2 (0.5 ears plant−1), but spikelet abortion took place in all apical ears after silking, except at 2 plants m−2 (control). Kernel number per plant was not related to the degree of floral differentiation reached at silking, but to the amount of intercepted photosynthetically active radiation (KN = 149.5 + 204.6 MJ plant−1 d−1, r2 = 0.92) when the silking −15‐d period was included in the calculations. Presilking limitations to ear growth appear to reduce ear sink strength.

Kernel Set and Flower Synchrony within the Ear of Maize : I. Sowing Date Effects

Maize (Zea mays L.) grain yield depends on the number of kernels per plant that reach maturity. In this work, associations between floral development within the ear and final grain number of maize hybrids differing in prolificacy were studied under nonstress conditions in Argentina. In one experiment at Rojas (34°08′S), four hybrids were sown on four dates, at 8 plants m−2, during 2 yr. Ears were observed at silking to determine the variation in the number of spikelets per ear. In the second experiment at Saito (34°33′S), a nonproliflc (DK638) and a prolific (DK 3S41) hybrid were sown at 7 plants m−2 on three dates. Ears were examined between the three‐leaf stage and silking + 12 d to determine floral differentiation. No sowing date effect was evident for the number of spikelets per ear, the number of rows per ear, or the number of spikelets per row, but hybrids differed for thesecharacters (P < 0.05). During active spikelet initiation, spikelet number in apical ears increased at a rate of 0.13 (DK 638) or 0.17 (DK 3S41) spikelets per row per °Cd. At silking, almost nil spikelets along a row in the apical ear had completed floral development in both hybrids, but the prolific type showed less spikelet abortion in the apical ear and a more synchronous development between ears. Kernel number per ear was independent of floral development stage at siiking, but was related to the rate of ear growth (in length) around silking. These results suggest that assimilate partitioning to the ear during this period is critical for kernel set.

Nitrogen fertilizer and foliar application of cytokinin affect spikelet and floret set and survival in oat

Yield potential of oat is only partly realized and both formation and expression of yield potential are largely environment dependent. This study was designed to monitor the possibilities for and efficacy of foliar applications of a synthetic cytokinin growth promotor (benzyl-aminopurine, BA) to enhance formation and realization of yield potential in oat ( Avena sativa L.). Comparison was made at 0 and 80 kgNha −1. BA was applied (0 and 10 −3 g a.i. 1 −1 at 300 L ha −1) when the apex was at the stage of initiation of floret abortion (i.e., close to booting stage). Three cultivars were included in the main field trials conducted at the Viikki Experimental Farm, University of Helsinki, Finland, in 1994 and 1995. Grain yield and 25 morpho-physiological traits were recorded. An additional BA-concentration response study was carried out using a modern cultivar (in 1994) and BA concentrations ranging from 10 −9 to 10 −1 g a.i. 1 −1. In both experiments, foliar applications of BA increased set of sterile spikelets. An increase in set of fertile spikelets and florets was recorded only in the BA response study between 10 −8 and 10 −3 g BAl −1. Nitrogen fertilizer application induced similar effects with the exception that set of sterile spikelets was not enhanced. In the BA response study, spikelet abortion increased with increasing BA application rate as numbers of sterile spikelets per panicle increased. Nitrogen applications increased chlorophyll content of the flag leaf and prolonged maturation, whereas BA treatment produced no consistent effects. Nitrogen fertilizer application increased panicle and grain filling and delayed senescence, but did not reduce abortion of spikelets and florets.

Temperature Effects on the Duration of the Spikelet Growth Phase and Spikelet Abortion in Barley

AbstractAbove optimal temperatures in cereals, when measured in thermal time units (°Cd) can lead to underprediction of developmental events by models, particularly when cereals are sown late in Mediterranean‐type environments or grown under subtropical conditions. Our objective was to assess the effects of high temperatures on the length of the spikelet growth phase, the number of spikelet nodes per spike and level of spikelet abortion in spring barley (Hordeum vulgare L.). The spikelet growth phase (from the end of the spikelet initiation phase to anthesis) of three cultivars, ‘Bandulla’, ‘Schooner’ and ‘Weeah’ was subjected to two temperature regimes. In the first of two sowings, the mean daily maximum temperature for one regime was 24 °C (maintained for 6 h daily) and the mean daily minimum was 8 °C (24/8 °C). The second temperature regime was 27/17 °C. Corresponding temperatures for the second sowing, which was subjected to slightly longer photoperiods, were 26/8 °C and 26/17°C, respectively. The duration of the spikelet growth phase was longer for 27/17 °C than for 24/8 °C in the first sowing when measured in calendar time (d). In the second sowing, the duration of the spikelet growth phase was slightly shorter under the higher temperature regime (d). The duration of the spikelet growth phase (in°Cd) was greatly increased by the higher temperature treatment in both sowings. In the first sowing, the percentage of aborted spikelets was greater at HT than at LT for Bandulla and Weeah at both sowing times and the duration of the spikelet growth phase increased with higher night temperatures, suggesting that length of the spikelet growth phase was not the sole factor responsible for the proportion of aborted spikelets.

Apical Development and Growth of Barley under Different CO2 and Nitrogen Regimes

AbstractIncreases in atmospheric carbon dioxide (CO2) concentration have stimulated interest in the response of agricultural crops to elevated levels of CO2. Several studies have addressed the response of C3 cereals to CO2, but the interactive effect of nutrient supply and CO2 on apical development and spikelet set and survival has not been investigated thoroughly. Hence, an experiment was conducted in the greenhouse to evaluate the effect of high (700 μmol CO2mol−1 air) and low (400 μmol mol−1) levels of atmospheric CO2 on apical development, spikelet set and abortion, and pre‐ and post‐anthesis growth in spring barley (Hordeum vulgare L.) grown under high N (0.3 g N pot−1 before sowing −1–0.11 g N pot−1 week−1) and low N (0.3 g N pot−1) regimes. The plants were grown in 5 L pots. Development of spike was hastened due to CO2 enrichment, and the C+ plants pollinated few days earlier than the C— plants. Carbon dioxide enrichment had no effect on date of ripening. Development of spike slowed following application of extra N, and plants pollinated 10 days later and matured 2 weeks later when compared with plants under low N. Carbon dioxide enrichment did not affect the number of spikelets at anthesis. Excess N decreased spikelet abortion and the increased maximum number of spikelets under both [CO2]. Barley plants did not tiller when grown in low [CO2] and low N. Increased endogenous IAA concentration in those plants, recorded three days before tillers appeared in other treatments, may have contributed to this. Carbon dioxide enrichment increased the C concentration of plants, but decreased the N concentration under high N regime. Both the C and N concentration of plants were increased under high N regime. Carbon dioxide enrichment increased the total dry matter of mature plants by 9 % under high N regime and by 21 % under low N regime. Under high [CO2] increased kernel number on tiller spikes, and increased kernel weight both on main stem and on tiller spikes resulted in a 23 % increase in kernel yield under low N regime and 76 % increase in kernel yield under high N regime. The rate of N application influenced growth and yield components to a greater extent than CO2 enrichment. At maturity, plant dry matter, kernel weight, the number of kernels per spike, and the number of spikes per plant were higher under high N regime than under low N regime.Long days (16 h), low light intensity (280 μmol m−2s−1), and at constant temperature of 20 °C high [CO2] increased kernel weight and the number of kernels on tiller spikes under high and low N application rate, but did not increase the number of kernels on main stem spike, or the number of tillers or tiller spikes per plant.

Variation in development of contrasting rice cultivars

SummaryExperiments were conducted in glasshouses at IRRI, Philippines, during 1987 and 1988 to identify varietal differences in apical development using six rice cultivars having extreme characters; Jirasar 280 (early senescence), Neo-Dunghan 1 (late senescence), Macunting (small seeds), ABB (large seeds), C12474–1 (long culm), and B581–A6–458 (short culm); and five cultivars, IR20, IR22, IR34, IR54, IR64, of the same growth duration.The length of time from physiological panicle initiation (PI) to flowering varied from 25 to 50 days. The onset of physiological PI occurred when the fourth penultimate leaf was fully exserted. The visual panicle initiation stage (VPI) coincided with spikelet differentiation in all cultivars. Nitrogen top-dressing at 55–57 days before the anticipated maturity date (the present N management recommendation) did not coincide with the actual panicle initiation stage in any of the cultivars and the major yield determinants (i.e. the primary and secondary branches) therefore differentiated in conditions of internal nitrogen shortage. Spikelet abortion took place both before and after flowering. Reduction of pre-flowering abortion is important in increasing rice grain yields and could be achieved by improved N management. It is important to recognise cultivar differences and periods of loss of potential yield in developing efficient N management protocols.

Lowland Rice Apical Development: Stages and Cultivar Differences Detected by Electron Microscopy

AbstractIdentification of growth stages and cultivar differences are necessary to develop efficient N fertilizer management for lowland rice (Oryza sativa L.). To help characterize growth stages an electron microscope was used to identify different panicle development stages, cultivar growth differences, and potential yield loss periods. Varieties IR50 (90‐d maturity) and IR42 (120‐d maturity) were grown at the International Rice Research Institute during the 1987 wet season. Thirteen morphologically different development stages up to floral organ development were identified. Between cultivars, duration of each development stage varied. Necknode differentiation was defined as physiological panicle initiation (PI) and observed at growth stage (GS) 1.8 occurring 35 days after seeding (DAS) in IR50 and at GS 1.10 (49 DAS) in IR42. Visual panicle initiation (VPI) was observed at GS 1.9 (42 DAS) in IR50 and at GS 1.11 (64 DAS) in IR42. Panicle development took 15 to 18 d (4–7 d for panicle branches) in IR50 and 24 to 31 d (11‐15 d for panicle branches) in IR42. Therefore the present N management practice of N topdressing 5 to 7 d before VPI coincided with PI for short duration IR50 but not for later maturing IR42. Preflowering and post flowering spikelet abortion reduced the spikelet number in IR50 and more so in IR42 where preflowering spikelet abortion started even before spikelet development was completed. Comprehensive N timing studies based on rice apical development stages are required for improving N efficiency and increasing rice yields.

A comparison of spike and spikelet survival in mainstem and tillers of barley

SUMMARYInitiation and abortion of spikelet primordia on primary tillers and mainstem were compared for plants of spring barley, Maris Mink, sown on two sowing dates during 1983, in plots at the Scottish Crop Research Institute (SCRI) and at Long Ashton Research Station (LARS). Sowing date had no effect on the number of spikelets initiated on either mainstem or surviving tillers and many more spikelets were initiated on equivalent stems at LARS than at SCRI but more spikelets aborted at the former site. The final number of spikelets produced was eventually similar. Spikelet abortion was complete by anthesis and coincided with the period of rapid stem and rachis elongation and with the time over which tiller death occurred. Despite the fact that plants at SCRI produced fewer fertile tillers they outyielded those at LARS because much heavier grains were produced on the mainstem and tiller 1 of plants at the Scottish site. An interval of 2 wk between sowing had only small effects on the components of yield.