Primary Florets Research Articles

The Effect of Postharvest Treatments on Flower Quality and Vase Life of Cut Alstroemeria ‘Dancing Queen’

Abstract Alstroemeria is one of the most popular cut flowers in Europe, due to its postharvest longevity and a wide colour palette. However, premature leaf yellowing reduces the ornamental value of the flowering stems even before opening of the secondary florets in cymes. The aim of this study was to evaluate the use of sucrose, gibberellin and 8-hydroxychinoline citrate as postharvest treatments of cut Alstroemeria ‘Dancing Queen’. Several “flower models” were used to distinguish the effects of the chemicals on senescence of flowers and leaves in the above cultivar. Flowering stems were harvested in November 2011 and March 2012 and the response to treatments for both dates differed: while the longevity of primary and secondary florets was prolonged by the standard preservative (8-HQC+S) in the autumn, there was no difference for the spring collection date. For the March harvest, the secondary flower buds opened faster than for the November harvest, where bud opening was generally hastened by 8-HQC+S. Also, the flower model affected floret longevity and changed the response to the treatments: florets on defoliated flowering stems responded better to the preservative than those on stems with leaves. Florets from different flower models differed in diameter: those from complete stems were usually larger than those from isolated cymes. The secondary florets were much smaller than the primary florets, especially in isolated cymes. Both, GA3 and the standard preservative significantly increased the second floret diameter in all models; however, there were no additive effects of the treatments. GA3 significantly postponed leaf yellowing in all floral models while the sugar-containing preservative had little effect. Generally, the flower model had significant effect on leaf longevity.

Resistance in winter wheat lines to deoxynivalenol applied into florets at flowering stage and tolerance to phytotoxic effects on yield

In Europe and North America, deoxynivalenol (DON) is the most prevalent mycotoxin associated with wheat head blight caused by Fusarium graminearum and Fusarium culmorum. Because DON is toxic to plants and enhances the ability of the pathogen to spread within a spike, wheat lines with resistance to DON should be more resistant to head blight. Resistance to DON has been associated with resistance gene Fhb1 that confers resistance to spread within a spike. The objectives of this study were to determine if wheat lines resistant to head blight were also resistant to DON, if genes other than Fhb1 confer resistance to DON, and to identify lines able to fill grain in the presence of DON. Susceptible controls and diverse North American and European winter wheat lines with resistance to head blight were screened for molecular markers linked to known head blight resistance genes, and evaluated in a greenhouse for resistance to DON and relative yield after application of DON to spikes at flowering. Fhb1 appeared to have the unique ability to confer resistance to DON, as measured by the number of DON‐bleached primary florets. However, this resistance did not protect plants from the phytotoxic effects of DON on kernel formation as measured by the relative yield of treated spikes. Furthermore, measuring the relative yield loss following DON application may be useful for identifying lines with tolerance to head blight.

Pollination dynamics, grain weight and grain cell number within the inflorescence and spikelet in oat and wheat

Oat (Avena sativa L.) and wheat (Triticum aestivum L.) vary in the structure of their inflores-cences and also in how pollination proceeds within the inflorescence. In both species the grain position in the spikelet determines grain weight potential. Primary grains in oat and proximal grains in wheat weigh more than secondary and distal grains. This variation in grain weight can potentially result from differences in post-pollination cell division in the grain. In this study pollination duration and dynamics were analyzed from head samples collected at two-day intervals, starting from the pollination of the most advanced floret. The number of grain cells was determined for individual grains throughout the inflorescence, starting from the pollination event. When mature, grain position in the spikelet and spike was noted and grain weight assessed. Pollination advance in oat proceeded from the uppermost primary floret towards the basal spikelets in ten to eleven days. Within the spikelet, the primary floret was pollinated on average one day earlier than the secondary floret. In wheat, pollination duration was four to five days, starting from the proximal florets in the mid-section of the inflorescence progressing towards the apical and basal spikelets. Proximal florets were pollinated one to two days earlier than distal florets. Maximum cell number in primary grains exceeded that of secondary grains in two oat cultivars. Similarly, primary grains were heavier than secondary grains. Cell number and single grain weight were correlated in terms of grain position in the spikelet (primary – secondary) and cultivar. Oat cultivar Belinda had a higher single grain weight than Fiia, which was also expressed as larger grain cell number. In wheat, proximal grains had higher maximum cell numbers and were also heavier than distal grains. This grain weight gradient was apparent throughout the inflorescence. Consequently, grain cell number is one of the possible regulators of grain-filling capacity in both cereal crops.

Effect of accel on the vase life and post harvest quality of alstroemeria (alstroemeria aurantiaca l.) cut flowers

Freshly cut flowering stems of Alstroemeria ‘Yellow King’ and ‘Marina’ were placed in glass jars containing solutions of Accel at 0, 25, 50, 75 and 100 mg/litre BA equivalent and arranged in a completely randomised design with 3 replicates. The effect of Accel on the vase life and qualityof Alstroemeria was investigated. Flowers held in Accel at 25 or 50 mg/litre BA equivalent consistently increased the number of days to full opening of primary florets and delayed the onset of flower senescence as measured by days to 50 % petal fall and days to 50 % leaf yellowing. Accel at 25mg/litre BA equivalent significantly increased the leaf nitrogen and chlorophyll content of Alstroemeria cut flowers. High Accel concentrations of 50, 75 and 100 mg/litre BA equivalent reduced significantly the leaf water content of Alstroemeria cut flowers. Accel at 75 and 100 mg/litre BA equivalentincreased leaf dry weight of Alstroemeria cut flowers. Our results indicate that Accel at 25 mg/litre BA equivalent has the potential to be used as a commercial cut flower preservative solution for delaying flower senescence, prolonging the vase life and enhancing post harvest quality of Alstroemeria cut flowers

Intra-plant variation for progress of cell division in developing oat grains: a preliminary study

Development of an oat panicle proceeds from the uppermost terminal spikelet downward to the base of the panicle. The intra-panicle variation in development is likely to influence potential grain size. This may result from differences in activity and duration of the cell division phase, vascular transport capacity, duration of filling period and/or hormonal balance. In this preliminary survey we studied intra-panicle variation in pollination (when clusters of pollen were visibly attached to stigmatic branches) of florets and cell division in developing grains immediately after pollination of the oat cultivars Belinda and Fiia. We found substantial intra-panicle variation for both traits. The highest cell number was found in the uppermost, most advanced, primary grain, while secondary grains tended to have fewer cells compared with their counterpart primary grains irrespective of their position. Results of an additional experiment indicated that death of the primary floret in the conventional oat cultivar Virma prior to pollination, resulted in higher weight of secondary grain, though this never equalled that of the primary counterpart. This limited growth capacity may partly result from lower cell number. These results encourage us to continue with experiments on the contribution of groat cell number to sink strength and grain-filling capacity.;

Effect of Benzyladenine on the Vase Life and Keeping Quality of <i>Alstoemeria</i> Cut Flowers

Two experiments were conducted to investigate the response of Benzyladenine (BA) on the vase life and the physiological changes in the leaves of Alstroemeria cut flowers. The treatments were combined in a factorial manner and laid down in a completely randomised design with 3 replicates. Treatment of Alstroemeria cut flowers with 25 or 50 mg/litre BA consistently increased the number of days to full opening of primary florets and delayed the onset of flower senescence as measured by days to 50 % petal fall and 50 % leaf yellowing. BA at 25, 50 or 75 mg/litre increased both the leaf nitrogen and chlorophyll content of the Alstroemeria cut flowers compared to the control. However, 75 and 100 mg/litre BA gave the highest values of leaf dry weight. BA decreased the leaf water content of Alstroemeria cut flowers. These results suggests that 25 mg/litre BA has the potential to be used as a commercial cut flower preservative to prevent leaf yellowing and prolonging the vase life of Alstroemeria cut flowers . KEY WORDS: Alstroemeria , benzyladenine, post harvest quality, vase life J. agric. Sci. technol. Vol.5(1) 2003: 91-105

Calcium and Nitrogen Fertilization of Alstroemeria for Cut Flower Production

The effects of Ca and N on cut flower production of Alstroemeria were determined in separate greenhouse experiments. Calcium was supplied as Ca(NO3)2 and CaCl2 at 0, 1, 2, 4, 8, and 12 mmol·L-1 added to tap water containing Ca at ≈0.2 mmol·L-1. Nitrogen was supplied as KNO3 and Ca(NO3)2 providing total N at 0, 3.5, 7, 14, 28.5, and 57 mmol·L-1 in tap water containing N <0.2 mmol·L-1. Nutrient solutions were applied at 7- or 10-day intervals to plants growing in a soilless medium in 2.6- or 5.5-L containers. Flowering stems were harvested when the primary florets opened. Total N concentration was measured in leaf tissue from the upper portion of flowering stems. Flower production was not affected by Ca supply, but increased with N supply to a maximum of about four stems per plant on a weekly basis at 28.5 mmol·L-1, then decreased to less than three stems per plant at 57 mmol·L-1. Nitrogen concentration in leaf tissue on a dry mass basis was maintained at 45 ±3 g·kg-1 in plants supplied with N at 28.5 mmol·L-1, 52±5 g·kg-1 at 57 mmol·L-1, but <40 g·kg-1 with N supply of 14 mmol·L-1 or lower. Nitrogen fertilization of Alstroemeria should be managed to maintain leaf tissue N close to 45 g·kg-1.

Expression of barley yellow dwarf virus and Russian wheat aphid resistance genes in and fertility of spring wheat × triticale hybrids and backcross lines

The Barley Yellow Dwarf Virus disease (BYDV) and the Russian wheat aphid (RWA) Diuraphis noxia (Mordvilko) have caused significant losses to wheat and barley in several areas of the world. Important sources of resistance to both BYDV and RWA have been found in Triticale. Different generations of interspecific wheat x Triticale crosses were produced and the progenies were screened for BYDV and RWA tolerance. Plants with equal chromosome numbers showed different levels of fertility. A significant correlation was observed between pollen fertility and seed set in primary florets (r=0.57). In generaL, pollen fertility, seed set and the number of euploid plants (2n=42) increased from one generation to the next. The expression of BYDV tolerance varied from population to population. Additive effects were predominant in F1 and some backcross populations. A dominant effect of rye tolerance genes was also observed in few populations. A monogenic trait or a quantitative (polygenic) character would not agree with the observed segregation patterns. The heritability of this oligogenic tolerance was quite different between populations and in many populations the tolerance genes were only partially expressed. Some transgressive segregation for tolerance and sensitivity was demonstrated. The genes controlling tolerance to RWA in Triticale lines, Muskox 658 and Nord Kivu were not expressed in advanced lines resistant to BYDV. This indicates that tolerance genes for BYDV and RWA in these lines are located on different chromosomes.

Postharvest Handling of Alstroemeria

Abstract Vase life of Alstroemeria hybrida ‘Regina’ was longest in inflorescences with secondary and tertiary florets. The presence of additional florets on a cyme decreased the vase life of the primary floret. Maximum flower opening and normal coloration occurred when the primary florets were harvested at the “rolled petal stage”. Cutting Alstroemeria stems above the blanched portion of the stem before placement in water increased water uptake and vase life. When secondary florets were present, leaf removal did not decrease vase life.

EFFECTS OF ARTIFICIAL REDUCTION IN PANICLE SIZE ON WEIGHT OF SECONDARY SEEDS IN OATS (Avena sativa L.)

Reductions in panicle size of oat (Avena sativa L.) by spikelet removal and sterilization of primary florets were used to study the growth potential of secondary seeds. Treatments to reduce panicles to three sizes, representing 25, 50 or 75% of the average number of secondary seeds in a panicle, were applied either at anthesis or 14 d later. Experiments included either two or four genotypes. Statistical analyses indicated that secondary seeds had a greater potential for growth than found in intact panicles. Grain weights in the treated panicles were significantly higher than secondary seed weights in control panicles when treatments were applied at anthesis. For the postanthesis treatments, seed weights in treated panicles were generally higher than control weights though the differences were not always significant. While large-seeded genotypes achieved higher seed weights under sink reduction treatments relative to their controls, the increases were not proportionally greater than those found for the smaller seeded genotypes. Secondary seed weights in the treated panicles were never as high as primary seed weights in the controls. The three levels of sink reduction affected grain weight differently in only two of the experiments. For these, genotype × level of treatment interaction effects were evident.Key words: Oat, Avena sativa L., secondary seed weight, panicle size

Studies on the inflorescence of wild oats (Avena fatua)

Some observations and experiments were carried out on inflorescences of wild oats, Avenafatua L. (Poaceae). Results of these studies indicate that the distal spikelets are initiated and mature earlier than those in the proximal positions. In each spikelet, the primary floret matures earlier than the secondary floret. However, the less mature secondary floret drops from the spikelet sooner. The awn in mature florets is geniculate and shows a characteristic twisting movement depending on the availability of moisture in the atmosphere. The movement of awns results in periodic dislodging of mature florets from spikelets. The basipetal maturity of spikelets in the panicle, the acropetal maturity of florets in each spikelet, and the premature separation of florets aided by the awn movement produce caryopses of variable maturity and are of considerable significance in the reproductive biology of wild oats.

A STUDY OF STERILOID CHARACTERS IN A MONOTELOSOMIC LINE OF CULTIVATED OATS, AVENA SATIVA

Three telosomic lines ST-20L of cultivated oats, Avena sativa L., were studied for their different expression of spikelet characters. An A sterilis type of spikelet was observed in one monotelosomic line in contrast to the A. sativa type (exception for one reduced twisted geniculate awn on the primary floret only) present in its monosomic counterpart. The genes responsible for cultivated vs. wild type spikelet characters were located on the short arm of ST-20, and the expression of the wild characters was found to be influenced by other suppressors located on chromosome(s) other than ST-20. It seems that the suppression of wild types of spikelet characters in cultivated oats is governed by more than one gene complex located on different chromosomes.

INHERITANCE OF STEM RUST RESISTANCE AND OTHER CHARACTERISTICS IN DIPLOID OATS, AVENA STRIGOSA

With the appearance and rapid increase of the highly virulent race 6AF of stem rust (Pucciszin grnmiszis Pers f. sp. nves~ne Eriliss. and Henn.) in North America (Stewart, et nl., 1962; Green, 1963) emphasis has been placed on finding new sources of resistance. McKenzie and Green ( 1965) reported on the inheritance of gene H which confers resistance to race 6AF; however, some biotypes of 6AF have been found that can attack plants with this gene. The successful transfer of crown rust resistance from the diploid Avenn strigosn Schreb. to the hexaploid A . sativn L. (Zillinsliy and Dericlt, 1960; Dyclt and Zillinsky, 1963) and the urgent need for additional sources of stem rust resistance has prompted work on transferring the excellent stem rust resistance of A . strigosn to hexaploid oats. This report presents data on the inheritance of resistance to stem rust in diploid oats and the association of stem rust resistance with other characters. Materials and Methods T h e identity of the parental strains, their stem and crown rust reactions and morphologic descriptions are given in Table I. Only the parental characteristics used for genetic analysis are shown. Tests of rust reaction were conducted on F, plants or F, lines in the greenhouse during the winter months. For stem rust inoculations, an oil suspension of urediospores was sprayed on seedlings in the first-leaf stage. For crown rust inoculation, a water suspension was used on I+ to 2-leaf stage seedlings. Approximately 25 seedlings were used of each F3 line. Races 1, 2, 2F, 6, 6A, 6AF (Eastern), 6AF (Western), 6F, 7, 7A, 8, 8AF and 13A of stem rust and races 264 and 294 of crown rust were used. For classification of growth habit, about 30 seeds of each of the F, lines from the cross C.D. 4482 x C.I.3078 were sown in the field. Plants or lines classified as prostrate remained prostrate throughout the summer and failed to head. Seedlings of crosses C.D.4482 x C.I. 3078 and C.D. 3820 x C.D. 7994 were classified for plant pubescence. Basal attachment (wild or sucker mouth vs. normal), and pubescence and nonpubescence (glabrous) of the Iernrna were classified in the C.D. 4482 x C.I. 3078 cross. In crosses between A. weistii Steud. or A. hirtula Lag., having a suclter mouth or wild base, with A. brevis Roth. or A. strigosn, having a normal base, Jones (1940) observed four different basal types which he designated and described as follows: XY typical wild type on both primary and secondary florets; Y base of primary floret similar to wild type, but suclter mouth restricted, base of secondary floret similar to normal type; X a pedicel remains adherent to base of primary floret, rachilla remains attached to secondary floret when separated from primary as occurs in the species A. sterilis L.; xy normal base. The A. brevis (C.D. 4482) used as the parent with the normal base in cross C.D. 4482 x C.I. 3078 rarely produces a secondary floret under conditions in which the F? population was grown. Thus many of the F2 plants produced primary florets only, making it impossible to