The POLLEN PRODUCTIVITY AND MORPHOLOGY OF POLLEN GRAINS IN TWO CULTIVARS OF HONEYBERRY ( LONICERA KAMTSCHATICA ( SEVAST . ) POJARK . )

In the years 2004 2006, investigations on the abundance of pollen production in two cultivars of Lonicera kamtschatica (Sevast.) Pojark. Atut and Duet, were conducted at the Felin Experimental Farm of the Agricultural University in Lublin. Moreover, the viability of pollen grains was estimated and me asurements of their size were taken. Ten flowers of both studied cultivars supplied 11.42 mg of pollen and the average pollen pro ductivity per 1 ha of a several years old plantation was 30.04 kg. The pollen of the observed plants was eagerly collected by ho ney bees. Pollen grains of both cultivars are suboblate. Conside ring their size, they can be described as large ones (P 47.55 μm, E 60.37 μm). Pollen viability for both cultivars is high, about 95%.


INTRODUCTION
Honeyberry (Lonicera kamtschatica (Sevast.)Pojark.)berries ripe earlier than other fruits grown in orchards.Blooming of this species starts usually in the second half of April and finishes about the middle of May, coinciding with the period of high pollen demand by bee colonies.The aim of the present study was to estimate pollen productivity in two cultivars of L. kamtschatica, in the conditions of south-eastern Poland.Moreover, the viability and size of pollen grains in both cultivars were investigated.

MATERIAL AND METHODS
The study was carried out in 2004-2006 at the Felin Experimental Farm of the Agricultural University in Lublin.Two cultivars of Lonicera kamtschatica (Sevast.)Pojark.-Atut and Duet were observed.The distance between the plants in one row was 1 m and between the strips -1.2 m.The experiment was established on gray-brown soil which originated from medium heavy clay.The mechanical composition of the soil is typical for slightly acid, light silty clays.
The abundance of pollen produced by flowers was determined by the ether method (Wa r a k o m s k a , 1972), modified by S z k l a n o w s k a (S z k l a n o w s k a and P l u t a , 1984; S z k l a n o w s k a , 1995).Flowers for pollen samples were collected just before corolla opening, 3 times during the blooming period.Each time 4 samples were gathered.A single sample contained 50 mature anthers.Pollen viability was checked in standard semi-permanent slides stained with acetocarmine.Measurements of the length of the equatorial and polar axis were taken in equatorial view of pollen grains, mounted in glycerin-jelly slides.As regards the shape and size, pollen grains were classified according to Erdtman (1956).Pollen prepared for examination and photographs in SEM was not treated with acetolysis.
To evaluate the abundance of flowering, each year freshly opened flowers were marked and counted on a randomly chosen branch of eight shrubs of the investigated cultivars.The counting was performed every 2-3 days during the blooming period.Then, the number of branches per each shrub was determined and the flower number per plant was calculated.
The data were analyzed by two-way ANOVA followed by Duncan test at α= 0.05.

RESULTS
In the season 2004 and 2005, in the climatic conditions of Lublin, flowering of Lonicera kamtschatica occurred between 20 April and the middle of May.In late spring 2006, blooming of the shrubs started at the end of April and lasted until 18 May.
Flowers of Lonicera kamtschatica are protandrous.When flowers open in the morning, pollen starts to be exposed in the afternoon hours, whereas flowers opened in the evening start to release pollen the next day, before noon.The anthers in 5 stamens dehisced one by one.The process of pollen release lasted until the second or even third day of flower life, depending on the time of flower bud opening and the weather conditions.During dry and sunny weather, the flower life-span lasted 3-4 days.
Pollen grains of two cultivars studied are similar in size; however, in cv.Ducat the equatorial axis is significantly longer than in cv.Atut (Tab.1).The equatorial axis of cv.Atut pollen grains, the longer axis, ranged from 50 to 70 μm, on average -59.77μm.In the case of cv.Duet, the values were 45.25-71.25 μm and 61.46, respectively.The length of the polar axis for cv.Atut was in the range of 37.5-57.5 μm (mean 47.64 μm) and for cv.Ducat 40.0-58.75μm (47.46 μm), respectively.The range of P/E ratio, describing the shape of grains, was similar in both cultivars and it was 0.72 -0.89.The mean for cv.Atut was 0.81 and 0.77 for cv.Duet (Tab.1).
With such values of P/E ratio, pollen grains of both cultivars can be described as suboblate.In the case of cv.Atut, the mean percentage of suboblate pollen grains was 83.89, whereas the relative abundance of oblate and oblate-spheroidal grains was 8.05% each (Tab.2).In the cultivar Duet, the average percentage of suboblate, oblate and oblate-spheroidal pollen grains was: 70.28, 27.5, 2.2, respectively.In polar view, the shape of the pollen outline was convexo-tetragonal, sometimes almost square.In equatorial view, that shape was more or less oblate.The 4-aperturate pollen grains were the most common in the samples, but also sparse grains with five and three apertures were present there.The pollen viability in both the cultivars studied was high -95.63%(Tab.1).
The average mass of pollen obtained from flowers differed significantly between the cultivars and the amount of pollen produced in anthers did show a year effect within the cultivars (Tab.3).The cultivar Duet was a better pollen producer than the cultivar Atut.Ten flowers of the first cultivar supplied 12.12 mg of pollen, whereas the same number of florets of the second Observed in the following years of the experiment, an increase in pollen productivity in both cultivars was due to the growth of plants and, in consequence, to a growing abundance of their flowering.It was also caused by the variability of pollen mass produced by flowers in the consecutive years of study.Among insects working on the honeyberry plantation, honey bees, bumblebees and, occasionally, solitary bees were present.Numerous honey bee workers collected both nectar and pollen.The insects formed dingy yellow pollen loads.
* means followed by the same letters are not significantly different at α 0,05

Table 2
Relative abudance of different shaped pollen grains, according to P/E ratio, in two cultivars of Lonicera kamtschatica (Sevast.)Pojark.Abundance of blooming and pollen yield of flowers in two cultivars of Lonicera kamtschatica (Sevast.)Pojark.in2004 2006 in Lublin.means followed by the same letters are not significantly different at α=0,05 one -10.72 mg.The mean pollen productivity in cv.Duet varied widely in the consecutive years of study and is from 8.75 to 15.55 mg.For cv. Atut, the values ranged between 9.62 and 12.15 mg.The estimated average pollen amount obtained from 1 ha plantation of cvs Atut and Duet was 27.6 and 32.48 kg, respectively. *