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Compared to the formation of male generative organs, the development of female sporogenous tissue of the European larch (Larix decidua Mill.) is considerably delayed. The young megaspore mother cell (megasporocyte, MMC) is not observable until late October, a short time before the period of dormancy. In early spring, MMCs become moderately enlarged, with intensive accumulation of starch grains around the nucleus. At the end of the first 10 days of March the MMCs become more rounded in section and the nucleus moves towards the basal part of the cell (near the chalaza). The integument and nucellus become observable at that time and chromosomal strands are visible in the MMC nuclei. Meiosis of MMCs was observed from mid-March to early April. During that period the tip of the integument grows gradually over the nucellus and creates the stigmatic apparatus of the ovule. Instead of the expected tetrads, triads of linearly arranged unequal megaspores were observed in individual ovules at the beginning of pollen shedding. Immediately after meiosis of the MMC, massive growth of the functional chalazal megaspore occurs, along with intensive free-nuclear divisions. The nuclei become located near the megaspore membrane, whereas the whole central part of the developing female gametophyte is filled with an extraordinarily large central vacuole. During intensive growth of the functional megaspore, the innermost layer of the nucellar tapetum gradually disintegrates. This development stage lasts until early May, when the megaspore membrane segregates partially from the nucellar tapetum and the free-nucleate female gametophyte assumes an irregular sac-like shape. The cellular stage of the female gametophyte with typical pyramidal cells at its micropylar end is visible at mid-May. Then the vacuolated (so-called frothy) archegonia gradually forms. The disappearance of vacuoles and the division of the central cell were registered in late May. At the stage of the large female gamete (egg cell) and the small ventral canal cell, the archegonia become fully receptive for fertilization. Our observations indicate that the development of the free-nucleate gametophyte and the formation of cell walls among the nuclei are the most sensitive phases of ovule development in the European larch before fertilization. During these stages, numerous cases of degeneration of the female gametophyte were observed, along with the complete deformation of ovules. The reasons for frequent irregularities are discussed here; the influence of meteorological and nutrient conditions seems especially important.
Proportion of sapwood and heartwood in stems of European Larch (Larix decidua Mill.) origin from provenances experimental plot. The aim of this work was to statě wether the wood from different provenances of European Larch (Larix decidua Mili.) show differences in proportion of sapwood and heartwood in stems. Research were carried out on 56 trees erepresenting 6 provenances of larch: Bliżyn (10), Czerniejewo (5), Konstancjewo-Tomkowo (3), Krościenko (15), Rawa Mazowiecka-Trębaczew (6), Skarżysko (9). This plot is a part of unique research area established in 1966. Results show important differences between heartwood-sapwood proportion for two provenances: Krościenko - the heighest proportion (largest volume of heartwood) and Bliżyn the lowes proportion (least volume of heartwood). The other provenances show similar proportions.
The study is an attempt to determine share of sapwood and heartwood in stems of European larch trees from II and III class of age, grown in conditions of fresh coniferous mixed forest site (BMśw), fresh forest mixed site (LMśw), fresh forest site (Lśw). The highest hare of heartwood was observed in stems of European larch in conditions of fresh forest site Lśw, and the smallest in conditions of fresh coniferous mixed forest site (BMśw). Differences were also observed within the investigated classes of age, and higher share of heartwood observed in III class of age. The smallest share of heartwood characterized codominant trees and the highest dominant trees (from main tree stand in Kraft classification).
W pracy podano wyniki badań uszkodzeń krótkopędów Larix decidua Mill., spowodowanych przez owady - szkodniki fizjologiczne. Analizowane krótkopędy (łąсznie 22 690) pobrano 30 modrzewi rosnących na 3 stanowiskach w Ojcowskim Parku Narodowym w 1493 r. Stwierdzono 6 gatunków owadów, wśród których najczęściej występowały: Coleophora laricella Hbn. i Adelges laricis Vall. Dane opracowano przy zastosowaniu wskaźnika frekwencji oraz wskaźnika Agrella współ- występowania gatunków.
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It is commonly known that Japanese larch, Larix kaempferi was first introduced in Europe in Great Britain in 1861. In the presence of European larches, L. decidua it was not long before the first hybrids between these species, called Dunkeld larches (Larix × marschlinsii), emerged there. It was found that there were several hybrid larch trees in Estonia that sprouted before one of their parent species was introduced in Europe. One of the oldest Dunkeld larches growing in Tallinn is about 210 years old. The radial growth of three Dunkeld larches in Estonia (in the cities of Pärnu and Tallinn and in the manor park of Suure-Kambja) and the determination of their age by cumulative growth graphs are discussed, with consideration given to the available knowledge on the introduction of Japanese larch. The conclusion is that there may have existed earlier alternative introduction routes of Japanese larch into northern Europe via Russia.
A field study on insects inhabiting cones of Larix decidua Mill. subsp. polonica (Racib.) Domin, was carried out in the protected forest reserve "Modrzewie" and its surrounding (the Krościenko Forest District) in 2011. A total of 2210 cones (12 samples) from larches were collected for analysis and for rearing. Moreover 3600 seeds extracted from cones, were analysed. During the studies 1687 insect specimens were obtained. They belong to 4 orders: Hemiptera, Coleoptera, Hymenoptera and Diptera. The most numerous species was Megastigmus pictus (Först.) (Hym., Torymidae): 850 specimens including 4 males. M. pictus destroyed 10.94% of analysed seeds. Strobilomyia laricicola (Karl) inhabited 13.06% of analysed cones. Information on parasitoids are given.
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