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Tiller demography of Festuca pallens Host (Gramineae) in two dry grassland communities

Janisova Monika

Polish Journal of Ecology

2006

Vol. 54, nr 2

201-213

Tiller demography of a perennial caesposite grass Festuca pallens Host was studied on perm,anent plots in two types of dry grasslands. The field work was done in the Povazsky Inovec Mts. (Western Carpathians) during 1993-1995. The permanent plot in the Poo badensis-Festucentum pallentis was located on a steep, strongly eroded S-facing slope covered with dolomit outcrops, scree and sparse vegetation (20%) dominated by Festuca pallens. The permanent plot in the Festuco pallentis-Caricetum humilis was located on the even ridge planteau with shallow stony soil and vegetation covering about 70% dominated by Carex humilis and Festuca pallens. The aim was to estimate the basic characteristics of tiller life cycle in Festuca pallens: tillering, flowering, mortality and life span. Tillers of Festuca pallens are exclusively intravaginal with a leaf rosette and polycyclic (can live for more than three years). A proximate maximum life span of orthotropic tiller parts was five or six years. The proportion of flowering tillers in the studied populations varied between the years from 3% to 10%. The mortality of tillers due to flowering represented about 50% of the overall tiller mortality. Flowering was mostly accompanied by an intensive pregenerative tillering. Tillering culminated twice a year - in spring and in autumn. About a quarter of the axillary buds developed into daughter tillers immediately after their formation. The fate of tillers in terms of survival, flowering and daughter tiller production can be predicted by their size. Both components of tiller size - leaf number and leaf length - influenced the fate of tillers although the predictive ability was stronger for leaf number. The two studied populations differed significantly in leaf number, leaf length and the height of inflorescences. These characteristics are supposed to be determined by external habitat conditions. The individual tiller life cycle (survival, life span, daughter tiller production) did not differ between the populations, thus the factors by which it is determined seem to be identical. These results support the idea that the basic processes and structures of tiller ontogeny are internally fixed for each species while external environmental conditions can only induce variability in absolute size.

Krzewienie się żyta w niskich temperaturach w okresie jesienno-zimowym

Doroszewski A.

Woda-Środowisko-Obszary Wiejskie

2005

T. 5, z. spec.

107-118

Na podstawie przeprowadzonych doświadczeń z żytem stwierdzono, że faza krzewienia może przebiegać w stosunkowo niskich temperaturach. Gdy temperatura powietrza, mierzona na wysokości 2 m nad powierzchnią gruntu, wynosiła -3,2°C (średnia z 53 dni), przybyło 0,45 pędów żyta, gdy -2,5°C (średnia z 36 dni) - o prawie jeden pęd boczny, a gdy -2,5°C (średnia ze 175 dni) - o dwa pędy. Natomiast gdy temperatura wynosiła -0,4°C (średnia z 49 dni), liczba pędów zwiększyła się o 1,1, a gdy 1,2°C (średnia z 89 dni) - przybyło aż 11,6 pędów żyta. Krzewienie się w niskich temperaturach możliwe było w warunkach znacznej i długo zalegającej pokrywy śnieżnej, toteż rozwój roślin był uzależniony od temperatury najbliższego otoczenia. Proces krzewienia się następował już, gdy temperatura gleby wynosiła niewiele powyżej 0°C. Znaczne przyrosty liczby bocznych pędów żyta notowano w temperaturze niższej aż o 8,2 w 1998/1999 oraz 7,5°C w 1993/1994 i 1995/1996 od temperatury progowej 5°C, określającej początek i koniec wegetacji.

Growing season is a very important period in agriculture, which determines growth and yields of plants. The growing season commences when daily average air temperature is ≥ 5°C and ends when air temperature is ≥ 5°C. Experiments carried out with rye showed that a phase of tillering may proceed at a relatively low temperature. In a period of time, when air temperature measured 2 m above the ground surface was -3.2°C (average of 53 days), the number of shoots rose by 0.45, whereas at air temperature equal -0.4°C (average of 49 days) the number of shoots increased by 1.1 and by one shoot when air temperature was -2.5°C (average of 36 days). Furthermore, there were 11.6 more shoots when air temperature was 1.2°C (average of 89 days). The tillering of rye was possible at low temperature with considerably thick and long lasting snow cover. Growth of rye depended on temperature of the nearest surroundings (soil), the process of tillering occurred at a temperature just above 0°C. Remarkable increments in the number of side rye shoots were noticed at temperatures lower by 8.2 in 1998/1999 and 7.5°C in 1993/1994 and 1995/1996 then a threshold value of 5°C, which defines the beginning and the end of the growing season.