Spikelet Number, Its Control and Relation to Yield Per Ear in Wheat

Abstract

For 12 cultivars of wheat grown under a 21°C day/16°C night temperature regime, spikelet number was closely related to grain number, but not to grain yield per ear as individual grain weights differed considerably between cultivars. However, when spikelet number was varied by day length or vernalization treatment, grain yield per ear was clearly dependent on spikelet number within each cultivar.An increase in spikelet number per ear was always associated with longer development. In cultivars with a pronounced response to vernalization (e.g. Late Mexico 120), the length of the period to floral initiation was of prime importance, because during this time potential spikelet sites were established; once floral initiation occurred, development of the inflorescence proceeded rapidly, and few further spikelet primordia were differentiated. In cultivars with no vernalization response (e.g. Triple Dirk), the duration of the period from floral initiation to terminal spikelet formation, during which all the spikelet initials appeared, determined spikelet number. The spikelet number of cultivars with a slight response to cold was associated with the lengths of both these periods.Spikelet number in Triple Dirk was modified by the number of long-day cycles to which plants were exposed; increase in the number of inductive cycles up to nine reduced the period from flOl'al initiation to the appearance of the terminal spikelet, and also reduced spikelet number per ear from 24 to 17. Exposure to only two longday cycles resulted in production of double ridges but caused slow inflorescence development thereafter, and there was an appreciable lag before a terminal spikelet appeared. However, development could be accelerated by exposure to further inductive cycles at any time before the spikelet primordia became swollen.

Wheat stem sawfly‐infested plants benefit from parasitism of the herbivorous larvae

“…Sawfly larvae cause most of the damage during the later developmental stages because food consumption and damaged nodes increase with exponential larval growth ( Morrill et al , 1994 ). This coincides with the grain fill period, after anthesis ( Talbert et al , 2001 ), when the number of seeds per plant is fairly well established but any stress that will reduce the rate of photosynthesis can affect the weight of the seed ( Rawson, 1970;Darwinkel, 1978;Bruckner & Frohberg, 1987 ). Reduction in wheat ear weight due to larval feeding has been reported to reach 22%, depending on the cultivar and the environmental growing conditions ( Holmes, 1977;Morrill et al , 1992;Ozberk et al , 2005 ).…”

Temperature, CO2 and the growth and development of wheat: Changes in the mean and variability of growing conditions

“…Note: (1) Results are for environments over cultivars and eultivars over environments. (2) Hay and Kirby (1991) summarised results from Rawson (1970) and Wall and Cartwright (1974), and reported that higher air-temperature treatments resulted in slower development, in terms of thermal time, in 17 out of 26 comparisons. However, Rawson (1970) reported daily applications of Hoaglands solution and watering, and this probably influenced soil temperatures more than the targeted air temperatures.…”

Effects of temperature on spikelet number of wheat

“…Effects of vernalization and photoperiod on spikelet number have been clearly demonstrated (Halse and Weir 1970;Rawson 1970) and Friend (1965) has also shown the effects of temperature and light intensity on spikelet number in Marquis wheat under conditions of continuous illumination. Rawson (1970) concluded that in cultivars with a pronounced response to vernalization, potential spikelet sites were established prior to floral initiation and few further spikelet primordia were differentiated subsequently. In cultivars with no vernalization response he found that spikelet number was determined by the duration of the period from floral initiation to terminal spikelet formation.…”

“…One way in which wheat yield can be modified by climatic adaptation is through the influence of various environmental factors on the number of the spikelets in the head as this affects grain number (Pinthus 1967). Effects of vernalization and photoperiod on spikelet number have been clearly demonstrated (Halse and Weir 1970;Rawson 1970) and Friend (1965) has also shown the effects of temperature and light intensity on spikelet number in Marquis wheat under conditions of continuous illumination. Rawson (1970) concluded that in cultivars with a pronounced response to vernalization, potential spikelet sites were established prior to floral initiation and few further spikelet primordia were differentiated subsequently.…”