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In a phytotron experiment, two hybrids of maize (LG 11 and Bastion) were exposed to different levels of temp., heat around noon, photoperiod and water supply at certain stages of development. Treatment influenced the flowering biology, but hardly affected leaf number. High temp. from tassel initiation until grain set increased the rate of development, but shortened the duration of pollen shedding; the interval between pollen shedding and silking was much longer. Thus the exposure of silks to pollen was curtailed. Grain set in the uppermost ear was hampered. The effect of extra heat from tassel emergence until grain set was minor. Long days from tassel initiation to tassel emergence delayed silking more than anthesis, thus increasing the desynchronization. Long photoperiods shortened the duration of the pollination period, but increased the number of female spikelets and the numbers of grains. Drought from tassel emergence until grain set delayed anthesis by 1-2 d and silking by 4 d. Drought did not consistently reduce the duration of pollen shedding, but impeded grain set. Many interactions between environmental factors and/or hybrid proved to be significant. Variation in number of female florets was partly explained by desynchronization of inflorescences. There was a highly significant (rsuperscript 2 = 0.64; n = 32) simple positive correlation between relative grain set and duration of the period of pollination of the silks by the plant's own pollen. The scatter around this relationship was mainly due to the effects of water availability on the functionality of male and female florets. The final number of grains was correlated closely with the desynchronization, although this relationship depended on hybrid and photoperiod. The environmental effects that influence flowering of maize are summarized in a simplified model of the dynamics of anthesis and silking. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Tillering in seed crops grown undisturbed for 6 months was studied over 2 years in cultivars of Setaria sphacelata, Chloris gayana, Panicum coloratum, Panicum maximum and Brachiaria ruziziensis. Tiller numbers rose to a maximum around the time of initial head emergence (5-10 heads/m2), followed by a decline and finally a levelling off. Head emergence was found to continue in some cv. for over 3 months. The weight/tiller increased at a linear rate. Tiller numbers never exceeded 1900/m2. Tillers were less numerous but were heavier in the year of sowing than in the subsequent year. Total dry weights of tillers were also highest in the first year. Seed yield was significantly correlated with degree of concentrated head emergence and percentage of heading tillers in a cultivar. It is suggested that, within cv., plants with heavier tillers may produce higher seed yields. Cv. within species can be identified according to date of initial head emergence. A type of culm branching is described in which tillers develop into flowering culms out of elevated nodes of erect parental culms. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Setaria sphacelata sown broadcast or in rows up to 100 cm apart was given 0-260 kg N/ha applied to each seed crop. 100 kg N/ha increased herbage DM yields 3-fold and yields of germinable seed 7-fold. At 130 kg N/ha yields of germinable seed were 33% higher from rows 30 cm apart than from rows 90 cm apart. Percentage and yield of germinable seed varied very greatly between seasons, though DM yield and inflorescence number varied little. The highest yield of germinable seed was 48 kg/ha for a single harvest. Rapid heading was preceded by a rapid increase and a subsequent rapid decline in tiller numbers. Herbage DM response to 100 kg N was 65 kg DM/kg N. (Abstract retrieved from CAB Abstracts by CABI’s permission)

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