4th Leaf Stage Research Articles

Control of Fall Armyworm in Whorl Stage Sweet Corn, 1987

Abstract A small-plot field experiment was conducted to screen insecticides for control of leaf-feeding damage to sweet corn seedlings by the fall armyworm. Sweet corn was planted 11 Aug in an Appling loamy coarse sand. The experiment was a randomized complete block design with 2-row plots, 20 ft long and 38 inches wide, with 5-ft alleys, replicated 5 times. Full-cone sprays were applied at 30 psi, directed over the whorl in a final volume of 25 gal/acre. Sprays were initiated when plants were in the 4th leaf stage at a time when 50% showed leaf feeding symptoms of 1st instar larvae. Plants were sprayed on 2, 9, and 16 Sep. On 9 and 28 Sep, all plants in each plot were rated for fall armyworm damage using the following 0-7 damage index: 0, no damage; 1, slight leaf feeding, but no indication of bud damage; 2, moderate leaf feeding, but no bud damage; 3, heavy leaf feeding and no bud damage; 4, slight to moderate feeding and slight bud damage; 5, moderate to heavy leaf feeding damage and moderate to heavy bud damage; 6, heavy leaf feeding and severe bud damage; and 7, plant virtually destroyed.

Undestructive measurement of acid phosphatase activity in the root of rice seedlings.

Conditions for undestructive assay system of acid phosphatase in the intact roots of rice ( Oryza sativa L.) seedlings as a marker of physiological activity of roots using p-nitrophenyl phosphate as a substrate were investigated Phosphatase activity was linear up to 3h at the concentrations from 0.5 to 10mM. Optimum acid phosphatase activity was obtained between pH 3 and 6 at 25-30°C. The enzyme activity of the whole roots including seminal and crown ones at the 4th leaf stage plant was higher than that at younger or older seedling stage. Using this method, we also investigated the effect of isoprothiolane (IPT), which is known as a plant growth regulator, on acid phosphatase activity in roots of rice seedlings. This compound promoted acid phosphatase activity in rice roots.

Yield Enhancement with Galecron, 1985

Abstract Galecron was applied at 0.25 and 0.125 lb (AI)/acre to determine if Galecron would enhance yield. Cotton was planted on 7 May and standard cultural practices for the Blackland of Texas were used. The experimental area was divided into equal halves by a 25 ft alley and the experimental design was a paired block with 0.125 and 0.25 lb (AI)/acre, Galecron being paired with a non-Galecron treatment. Thus, all Galecron plots were side-by-side and drift, vapor, etc. contamination to the non-Galecron was minimal as they were located down wind in the prevailing wind. Plots were 8 rows by 40 ft and replicated 4 times. To preclude the effects of cotton fleahoppers, the entire experimental area was sprayed with 0.25 lb (AI)/acre Azodrin each time Galecron was applied. All other insects were controlled as needed. Galecron applications were made on 13 Jun (6th leaf stage), 20, 25, and 1 Jul with a Hi-Boy sprayer at 5 gal/acre. Squares and bolls were counted by whole plant examination of 0.001 acre on 11 Jul and bolls on 30 Jul. Yield was obtained by stripping the two center rows on 6 Sep.

Tolerance of large crabgrass of different ages and strains to propanil.

Tolerance of large crabgrass of different ages and strains to propanil was surveyed, and the absorption of propanil by shoots and its hydrolyzing enzyme activity have also been studied.There were no great differences in susceptibility to the herbicide among large crabgrass plants from different locations in Japan at the 4th leaf stage. Significant difference in tolerance was found among large crabgrass plants at different ages, as well as barnyardgrass. The younger large crabgrass and barnyardgrass were more susceptible to propanil and tolerance to the herbicide incre ased as the leaf stage increased. Neither species of plant hydrolyzed the substance even at the 6th leaf stage. The concentration of 14C-radioactivity in large crabgrass at the 3rd leaf stage was much higher than at the 6th.Large crabgrass was shown tolerant to propanil only at the 6th stage, and differential tolerance to the compound in different strains was not found significant. It was suggested that the mechanism of tolerance of large crabgrass at the 6th leaf stage to propanil was not due to the detoxifying hydrolytic activity of the herbicide, but due primarily to the lower absorption of the compound by the shoots.

Tolerance of finger millet to propanil. 3 Relationship between propanil binding by chloroplast and inhibition of photosynthetic electron transport.

Difference in propanil binding to chloroplast and its inhibition of photosynthetic electron transport system among the three gramineous plant species were studied.Chloroplasts were isolated from rice, barnyardgrass and finger millet grown to the 3rd or 4th leaf stage. No significant difference was obtained among the species in either inhibition constant (Ki) of photosynthetic electron transport by propanil or its binding constant (K) to chloroplast. Specific binding of propanil was almost identical to its inhibition of electron transport. But the herbicide bound to rice chloroplast slightly more than to barnyardgrass or finger millet at high inhibitor concentration.It was concluded that there was no difference in either inhibition of photosynthesis by propanil or the herbicide binding to chloroplast among three species of plants.

Early Season Insecticide Study, 1985

Abstract The relative efficacy of 6 insecticide treatments was evaluated at Delta Branch Experiment Station, Stoneville, MS, in a randomized complete block design with 4 replications. Treatments were applied by high clearance tractors with 2 Teejet 4X nozzles/row aplying 6.5 gal/acre. Spray applications were begun at the 4th true leaf stage and reapplied on schedule for 6 applications ending after the 9 Jul application. Two treatments were included as maintenance treatments and were applied only once. Plants were scouted weekly by the whole plant method for Heliothis spp., boll weevil, plant bugs, and related damage. Plots were 4 rows (38-inch centers) by 50 ft with 2 untreated rows between plots. All plots were oversprayed with Lorsban at 0.05 lb/acre 15 Jul for aphid control. Aphids were scouted for 11 and 25 Jul in lower middle and upper regions of the plants by estimating aphids/leaf as 0, 1-5, 6-15, 16-25, and >25 for 10 leaves per replicate. Mean aphids per leaf were calculated from field data. There were no statistical differences in aphid numbers between levels within treatments and data were pooled. A center row of each plot was harvested mechanically 19 Sep.

Studies on the growth and productivity of maize for whole-plant silage in the north-marginal area, Nemuro district in Hokkaido.

The object of this report is to clarify the dry-matter accumulation habits during the early vegetative growth period and to investigate the effect of the early growth on yield and quality of maize for whole-plant silage in the north-marginal area in Japan (where accumulated temperature from May to September is 2200°C.). Experiments were conducted for 6 years (1978∼'83), based on the same design. Wase-homare (an eary hybrid) was planted on three dates from mid-May to early-June in 1978∼'82 and late-May in 1983. The dry-matter weight in each organ was measured at the 4th-, 7th-, and 11th-leaf fully developed stages, and dry-matter yields were measured at harvesting date. The results obtained were as follows : 1. Root dry weight growth rate in each growth period from emergence to the 11th-leaf stage showed highly positive correlations with leaf expansion rate and top growth rate (TGR)(Table 1). 2. TGR during the period from emergence to the 4th-leaf stage showed highly positive correlations with daily maximum temperature and sunshine hours, but was not correlated with solar radiation (Table 2). 3. TGR in each growth period from emergence to the 7th-leaf stage showed a highly positive correlation with LAI. TGR during the period from the 7th-leaf stage to the 11th-leaf stage showed highly positive correlations with both of LAI and NAR (Table 3). 4. TGR during the period from emergence to the 4th-leaf stage showed highly positive correlations with ear DM yield, total DM yield and percentage of dry-matter in whole-crop, but was not correlated with stover DM yield (Fig. 4). 5. Thus it was concluded that the early growth is of great significance on the growth and development of ears which are essential for stable and high yield, and high quality of maize for whole-plant silage under severe conditions in the north-marginal area.

Growth and Development Responses of Geranium to Temperature, Light Integral, CO2, and Chlormequat

Abstract “Red Elite” geraniums were grown from the 6th leaf stage until the visible bud stage in controlled environment (CE) chambers under 3 day/night temperature regimes (27°/13°, 23°/17°, or 20°/20°C) and under enhanced CO2 (900 μl CO2/liter air) at 27°/13°. Three daily light integral treatments, 24.6, 19.8, and 15.1 mol m−2 d−1, were imposed over each of these 4 treatments. Plants also were grown in a 22714° glasshouse with 2 daily light integral treatments (18.2 or 11.3 mol m−2 d−1). A chlormequat (CCC) drench was applied to half of the plants immediately before the treatments were started. For the period between the 6th leaf and visible bud stages, leaf area, leaf area ratio, specific leaf weight, shoot dry weight, leaf canopy height, and time to visible bud were determined mostly by daily mean temperature rather than by day or night temperature. Most plant growth characteristics, but not the flower bud development rate from 6th leaf to visible bud, were enhanced by supplemental CO2 and suppressed by CCC. After reaching the visible bud stage, plants from some treatments were moved into 24715° CE temperature conditions with or without CO2, whereas others were moved to a glasshouse until harvest at the 1st floret anthesis stage. Between visible bud and anthesis, CCC was the major factor affecting vegetative growth regardless of whether the plants were with or without supplemental CO2 in CE rooms, or in a glasshouse. Anthesis was delayed by about 10 days in the glasshouse compared to the CE treatments but was unaffected by CO2 or CCC treatments. Carbohydrate concentrations were highest (starch 14%, sugar 5%) in plant leaves grown with supplemental CO2 and without CCC, and lowest with no added CO2 but with CCC in all CE treatments. The concentrations were reduced (starch 0.5%, sugar 2.5%) in plant leaves grown in a glasshouse from 6th leaf stage to anthesis because of low daily light integrals and no supplemental CO2.

Effects of Split-night Temperatures, Light, and Chlormequat on Growth and Carbohydrate Status of Pelargonium × hortorum

Abstract Seedlings (72 or 48 days old) of Pelargonium × hortorum cv. Red Elite were grown in 1 experiment from the 6th leaf stage in controlled-environment (CE) rooms at 4 temperatures, including 2 split-night (SN) regimes and at 3 daily-light integrals; in a 2nd experiment they were grown at 2 temperatures including one SN regime, at 3 daily-light integrals, and with and without chlormequat soil drench. Each of the 2 night-temperature periods were of equal duration in the SN regimes. Plants grown under the SN regimes were either similar in growth and reproductive development to plants grown under constant night conditions, where the temperature was the mean of the 2 SN temperatures, or were generally intermediate in growth and development to plants grown throughout the night at each of the 2 temperatures used in the SN regime. A daily mean temperature of 20°C compared to 16.8° or 18° reduced the time between the 6th leaf and macrobud visible stages by 8 days. Leaf starch and sugar levels decreased as mean daily temperatures increased, but increased as daily-light integrals increased. Drenches of (2-chloroethyl)-trimethylammonium chloride (chlormequat) applied at the 6th leaf stage limited plant height and leaf area without influencing flowering date.

Insecticide Combinations for Heliothis Spp. Control, 1983

Abstract A field evaluation of insecticide combinations for Heliothis spp. control was conducted on sandy loam soil at the Plant Breeding Unit of Auburn Univ., Tallassee, Ala. Because of earlier stand failure cotton was replanted on 26 May in 40-in. rows. Four replicates of 10 treatments were included in a randomized complete block design. Plots were 18 rows by 100 ft with 25-ft alleys between blocks. Insecticides were applied with a high clearance sprayer at a rate of 9 gal/acre (2.0 mph, 60 lb/in2, 2 Teejet TX 80° nozzles per row). Plots evaluated for early season insect control were treated 8, 15, 22 and 29 Jul. with Fundal at 0.125 lb (AI)/acre beginning at 6th leaf stage. All plots were treated with test chemicals on 8, 12, 16, 30 Aug., and 12 Sep. Plots were oversprayed on 29 Jul. with methyl parathion to destroy beneficial insects and on 9, 15, 29 Aug., and 3 and 9 Sep. with Guthion to suppress boll weevils. Early season insect numbers were estimated by taking 3 ft by 3 ft drop cloth samples from two randomly selected areas of each plot. Heliothis spp. damage was estimated by examining 25 randomly selected plant terminals from the middle eight rows of each plot and by examining 25 randomly selected squares. Boll counts were taken from 10 row-ft randomly selected in the plot. Heliothis spp. populations were moderate to light during the test period.

Studies on Nitrogen Metabolism in Crop Plants : XVIII. Utilization of nitrogen fertilizer on leaf area growth, protein synthesis and sink formation in the rice plant

The present work was undertaken to investigate the effect of nitrogen top-dressed at the different growth stages in rice plants on its leaf area growth and on the nitrogen levels in the individual leaf blades, and furthermore to establish nitrogen translocation and distribution into the various plant parts. For these purposes, 15N-labelled ammonium sulfate was used as a tracer in order to measure absorption of nitrogen fertilizer, and to follow the translocation of absorbed 15N-labelled nitrogen into grains from the other plant parts. The results obtained are as follows. 1. A marked increase was found in leaf area growth of the rice plant by top-dressing of nitrogen during the growth stages of tillering to branch differentiation, but it was not found to occur after the boot stage. During the ripening period a decrease of the leaf area growth was significantly suppressed by top-dressing. The contents of total nitrogen, soluble and Fraction-1 proteins in the leaf blades greatly increased by top-dressing after the boot stage and these values were much higher than the corresponding values at the tillering and branch differentiation stages. 2. The leaf area growth of individual leaf blades was effectively promoted when nitrogen was top-dressed sometime before the emergence of the leaf in question. For example, the growth of 12th and 13th leaf area was more accelerated by top-dressing at the 11th leaf elongating stage and the growth of 13th and 14th leaf area by top-dressing at the 12th leaf elongating stage. However, after the boot stage nitrogen fertilization was ineffective on the leaf area growth. 3. Of the two rice varieties used, Kamenoo showed a relatively higher growth of leaf area as compared with Hatsukaori. By top-dressing of nitrogen, the increased leaf area growth was more obvious in the former variety than in the latter one. The extent of leaf area growth was marked when nitrogen fertilizer was top-dressed at the tillering or branch differentiation stages. On the contrary, Hatsukaori showed higher levels of total nitrogen, and soluble and Fraction-1 proteins in the leaf blades rather than increasing the leaf area growth by top-dressing of nitrogen. 4. The translocation of top-dressed nitrogen into individual leaf blades differed considerably with the growth stages at which labelled nitrogen was supplied. 15N-labelled nitrogen supplied at the tillering stage (11th leaf stage) tended to accumulate into the just elongating 12th leaf blades whereas 15N supplied at the stage of branch differentiation stage (12th leaf stage) was predominatingly translocated and deposited in the upper 13th and 14th leaf blades. However, after the boot stage little or no difference was found in distribution of 15N-labelled nitrogen among the individual leaf blades, and 15N-labelled nitrogen tended to accumulate mainly into the developing ears rather than the other plant parts (leaf blades and leaf sheath+culms). 5. The percentages of 15N distributed to sink were 52, 58, 70 and 72 for nitrogen top-dressed at the tillering, branch differentiation, boot and heading stages, respectively. These data agreed with the results that the grain-N content together with glutelin (one of the reserve proteins) increased markedly by top-dressing of nitrogen at the boot and heading stages.

Zymogram Analysis in Brassica Species

Studies were carried out to consider from the viewpoint of isozyme analysis some genetical relationships among Brassica genome types and to examine whether the isozyme method could be applied in identifying hybrids at an early stage of growth. Several varieties were selected from each Brassica genome type. Seeds were sown in pots at the end August. Plants at the 4th leaf stage of each genome type were collected and the stems were used as the material. In this experiment, peroxidase and esterase isozymes were analyed by starch gel electrophoresis. The starch gel was prepared in 0.03M borate buffer (pH 8.5), using hydrolyzed potato starch. The samples, approximately 1g in fresh weight, were ground with a homogenizer. The homogenate was placed on a filter paper strip, and the strip was inserted into the gel at a disttance of 8cm from the cathodal edge.

イネラギッドスタント病に対する日本稲の反応

Seedlings of 28 Japanese rice cultivars were all susceptible to rice ragged stunt disease. The symptoms observed were almost the same as those reported for TN1 except for occasional appearance of necrosis on a leaf of some cultivars. Remarkable differences were observed in the degree of stunting among the tested cultivars. In pot experiments, culm lengths of diseased plants were about 43% for Nipponbare and 81% for Reiho respectively of those of healthy ones. Cultivar Nipponbare inoculated at the 4th and 7th leaf stage showed typical symptoms, whereas those inoculated at the 10th and 12th leaf stage had no clear symptoms. Because of the absence of the productive culms, no yield was obtained from plants inoculated at 4th or 7th leaf stage. Inoculation at 10th leaf stage resulted in a 20% yield loss, mainly due to a decrease in percentage of ripened grains.

Studies on germfree higher plants

Abstract The effect of sucrose on the growth of rice plants under gnotobiotic conditions was studied at test tube scale in vinyl isolators under weak or strong light. Under weak light (500 lux) the growth of rice plants on agar medium containing only inorganic nutrients during the 20 days after transplanting stopped at 3rd leaf stage, whereas plants on agar medium containing inorganic nutrient plus 2% sucrose grew to 5th or 6th leaf stage. Under strong light (1.5 × 104 lux) the stage of tillering was promoted by supplying sucrose. The growth of rice plants in pot-hydroculture under weak light had the same tendency as that obtained in test tube culture under weak light. Considering the concentration of inorganic elements in rice shoots, it seems most likely that the uptake of inorganic elements. especially phosphorus and potassium, was enhanced by the supplements of 2% sucrose under weak light. An increase of calcium and manganese uptake was observed in plants grown in medium containing 2% sucrose compared with that of plants grown in inorganic medium alone under strong light. The uptake of inorganic elements from medium containing inorganic nutrients plus 2% sucrose depended chiefly on light energy under strong light in the phytotron used.

Varietal Differences in Root System and its Relationship with Shoot Development and Tuber Yield

Ten varieties were grown under the field conditions at the two locations, and number, diameter and dry weight of root were measured at the 4th leaf stage, the initial flowering stage and the full leaf expanding stage. The results obtained are summarized as follows: 1. Number, diamcter and dry weight of root attained to the maximum value about the initial flowering stage, and maximum diameter and dry weight of root were greater in late varieties than in early ones. 2. Number of roots per plant indicated a positive correlation with shoot numbcr (r=0.743), but dry weight of root per plant was correlated with dry weight of root per stem (r=0.792), not with shoot number. Moreover, maximum root diameter and dry weight of root correlated positively with stem length, number of leaves on main stem and stem diameter. 3. Root dry weight of each variety reached the maximum value several weeks earlier than shoot dry weight at each location. 4. During the period from the 4th leaf stage to the initial flowering stage, there were distinct differences among varieties in root and tuber growth rates. The growth rates in late varieties were higher in root, but lower in tuber, compared with early ones, and there was a highly negative correlation between them. However, varietal differences in growth rate per plant were very litte except Shimakei No. 161, and not related with the earliness. In addition, growth rates in each organ were correlated with their distribution ratios, not with growth rate per plant. 5. Root dry weight was significantly correlated with tuber yield. However, leaf and stem dry weight were greater in late varieties than in early ones and showed also highly significant correlations with tuber yield. Therefore, it was assumed that the relationship between root system and tuber yield was not due to the direct contribution of root system, but due to the pleiotropic expression of the earliness.

Effective Water Depth for Protecting Rice Panicles from Sterility Caused by Cool Temperature during the Booting Stage

The deep water irrigation is one of the most effective countermeasures against the sterility induced by a cool temperature at the booting stage. For the purpose of estimating the water depth necessary for protecting susceptible spikelets, the vertical distribution of spikeltts at the critical stage was surveyed in the whole panicles of a rice plant in paddy fields, uslng 4 varieties in Hokkaido during the years 1972 to 1975. The following relations were observed as to the height of susceptible spikelets above ground. Variety: Norin 20, Yukara > Eiko, Shiokari, Yunami. Year: 1973 > 1972. Fertilizer level : high > medium > low. Seedling age: 5th≒4th-leaf stage. Tiller: main stem > primary > secondary. The results of the present study showed that the water depth covering about 80% of the cool-susceptible spikelets is l7-20 cm and higher than the conventional 12-15 cm depth recommended by Sakai (1949).

カブの肥大に関する形態的•組織化学的観察

This experiment was carried out to study the thickening of turnips, by morphological, anatomical and histochemical methods.The process of the elongation and thickening of hypocotyl was observed from the morphological point of view, the anatomical changes of hypocotyl from the anatomical method, and the changes of the content of mono- and polysaccharide, nucleic acid and lignin from the histochemical point of view.The results were as follows: The elongation of hypocotyl stopped by the 6th leaf stage in all varieties used, while the beginning of thickening depended upon the variety used. In Yorii-kabu and Kanamachi-kokabu, thickening began at the 4th leaf stage. And at the 6th leaf stage, the thickening of the hypocotyl was visible to the naked eye. But, Koiwai-kabu did not begin to thicken even at its 10th leaf stage.Through the observation of the thickening of turnips, it was found that thickening began from the central part of hypocotyl and after that the thickening of the upper and lower part began. On the other hand, in the case of radishes, the main root was the first to thicken.In anatomical studies on the thickening of turnips, the following was observed: New phloem was formed at the xylem parenchematose tissues, which were situated inside the cambium ring which had been formed by about the 4th leaf stage, and became active. These active cells of the new phloem cut the cambium ring, and as the result, the tissue of the hypocotyl began to thicken. This phenomenon was not observed in other Brassica (B, pekinensis, B. oleracea, B. juncea…).In the histochemical observation of the hypocotyl of turnips even after the 4th leaf stage, the reaction of mono- and polysaccharide and nucleic acid was stronger than in those of non-thickened varieties. On the contrary, the hypocotyl of turnips scarcely showed the reaction of lignin, while the hypocotyl of those which had non-thickened varieties showed a very remarkable reaction.In another observed point of radishes and turnips, the cortex which had formed at their germinating stage was cracked and dropped out when their thickening began. It may be safely said that this phenomenon occurred because primary cortex could not stand the physical changes (thickening) of the inside tissue, which was confirmed both anatomically and histochemically.

Studies on the Pysical Characteristics of Rice Seedling : III. The Effect of Potash Application

To obtain suitable seedlings for mechanical transplanting, the effect of potash application was studied on the physical characteristics of seedlings at the 4th leaf stage. Zero to four g/box of potash (K2O) were applied as basal dressing to the seedlings grown in seedling boxes, which were filled with Kitamoto (K-deficient) and Konosu (standard) soils. 1. Physical characters of seedlings differed significantly by the difference in soils and by the amount of potash applied. Comparing with the seedlings grown in Konosu soil, those grown in Kitamoto soil were more rigid in the structure of basal part, thicker in basal section and more resistant to buckling and bending, which were due to the well developed basal part with erect and short foliage. A decrease in the rigidity in the basal part was observed as potash application was increased (Fig. 1). 2. Potash content in leaf sheath was closely related with the nature of soils and the amount of potash applied. High potash content was observed in the seedlings applied more amount of potash and this case was observed a also in the seedlings grown in Konosu soil. An increase in potash content resulted in the reduction of structural rigidity in basal part, with the increment in basal section diameter. This means that the resistance to buckling and bending decreases because of excessive foliage grown with poor developed basal part (Fig. 2). 3. So far as the information presented, no relations have been found between abundant potash application and the vigour of seedling. Therefore it is concluded that excessive potash application is not recommended because of the unfavorable physical characteristics for mechanical transplanting.

The effect of various environmental factors on flowering of gladiolus. III. Temperature and moisture

Under conditions of low light intensity in winter, low temperatures (1–4°C) increase the occurrence of flower blasting. This chilling damage was observed at two developmental stages — immediately after planting and at the 7th leaf stage when spike emergence starts. Gladioli are extremely tolerant to high temperatures (up to 50 °C) as long as air humidity and soil moisture are at an optimum. The damaging effect of high temperature is generally indirect via its effect on plant water balance. Plants were directly damaged by high temperature during the period from planting to the first leaf stage. Decrease in soil moisture reduced flowering at most stages of development. The stages immediately after planting and just before spike emergence were the most sensitive.

The effect of various environmental factors on flowering of gladiolus. II. Length of the day

In summer, shortening the length of the daylight period (SD) caused a decrease in either the flowering percentage of Gladiolus, or the number of florets produced per spike, or in both parameters according to the degree of sensitivity of the cultivar in question. In all cultivars tested, SD prevented the production of secondary inflorescences. Sensitivity to SD treatment differed at the various stages of development. Flowering percentage was especially affected by SD treatment when applied during the period lasting from emergence of the 1st to the appearance of the 5th foliage leaf. In contrast, SD applied from the 4th leaf stage to anthesis reduced the number of florets per spike. The stage from the appearance of the 4th leaf to spike emergence was most sensitive since both the flowering percentage and the number of florets per spike were reduced. The effect of SD treatment was similar to that of reduction in light intensity ( Shillo and Halevy, 1976) and is apparently due to a reduction in total solar irradiance. In winter, photoperiodic low light intensity extension of natural daylength (LD) delayed flowering and increased the number of florets per spike, the number of secondary inflorescences and sometimes also the flowering percentage. Plant response to LD treatment was similar at all stages of flower development.