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ABSTRACT

The effect of different injury periods and tree species composition of beech stands on change the structure of the barrier zone of xylem formed after injury was studied in this work. Findings at micro structure level confirmed significant differences in the structure of barrier zones and new xylem formed after injury. A strong barrier zones are formed in wounds originated in the middle growing season. However, barrier zones formed in wounds originated in the beginning and end of the growing season were narrower or interrupted, or not originated at all. In the wounds originated at the middle of dormant period were formed quite wide however short barrier zones. Also, microstructure of xylem formed after injury was different than micro structure formed before the injury. It was characterized by reducing the vessel diameters and increasing the proportion of fibers and simultaneous increase of the thickness the parenchyma rays. The results confirmed the significant impact of both observed factors on the differences in the ability to protect the cambium against infection and damage by pathogens.

Key words: Beech, growing or dormant period, air temperature, injury, barrier zone, wound wood.

ÚVOD

Mechanické poranenie povrchu kmeña (spôsobené prebierkami a fazbou) je castou pricinou poklesu ceny bukovej guFatiny. Povrchové odstránenie kôry spustí v zivom ströme celÿ rad fyziologickÿch obrannÿch a hojivÿch procesov (oddelenie a obrana infikovanÿch a zdravÿch pletív a tvorba kalusu), ktoré menia anatómiu a biochemickú povahu napadnutÿch pletív. Vo fytopatológii je vseobecne akceptovanÿ konceptuálny model styroch statickÿch obrannÿch stien "Compartmentalization of decay in trees" (CODIT model) (Shigo 1984; Shigo a Marx 1977). Podl'a modelu ohranicujú lézie anatomickÿmi stenami 1-4, ktoré ich uzatvoria v rámci vymedzeného priestoru. Steny 1-3 staticky bránia d'alsiemu síreniu nákazy v xyléme, ktorÿ bol vytvorenÿ pred poranením. Stena 1 je bariéra, obmcdzujúca axiálne sírenie infckcie cez cievny systém. Dochádza k tylatácii ciev a k ich vyradeniu z cinnosti. Silnejsia stena 2 obmedzuje radiálne sírenie lézií, pricom bariéru tvori hranica rocného kruhu. Vÿznamnù úlohu pritom zohráva terminâlny parenchÿm a hrubostcnné bunkové steny libriformnÿch vlákien lokalizované v letnom dreve. Stena 3 je este silnejsia hranica, zabrañujúca bocnému (tangenciálnemu) síreniu patogénov. Hranicu tvorí skoro nepreniknutel'ná zábrana parenchymu strzñovych lúcov (d'alej SL).

Na okrajoch sfarbenÿch lézií (vo vsetkÿch troch anatomickÿch smeroch) sa tvorí úzka tmavá "reakcná zona"...

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