Leaf chlorophyll (Chl) concentration can be an indicator of plant health, including photosynthetic potential and nutrient status. In some cases, this measure can indicate the degree to which plants are water-stressed. Traditional methods of measuring Chl concentration have involved a destructive sampling technique: extraction and spectrophotometric analysis. A compatible nondestructive method to measure leaf Chl concentration exists and applies transmittance spectroscopy to plants with a Minolta SPAD-502 meter. These techniques were evaluated by comparing leaf Chl concentration in big bluestem (Andropogon gerardii). Leaves were sampled from plants representing three ecotypes (originating from Central Kansas, Eastern Kansas, and Illinois, USA) and two cultivars of A. gerardii growing in Hays, Kansas, USA. Leaf Chl concentration was measured using nondestructive and destructive techniques. We documented a saturating relationship between destructively measured leaf Chl concentration and SPAD index resulting from a decelerating change in SPAD index as Chl concentration increased. The comparison of A. gerardii ecotypes and cultivars demonstrated highest Chl concentration in the ecotype and cultivar from areas with historically low precipitation, Central Kansas and A. gerardii var. hallii, respectively. A high ratio of Chl a to Chl b is an index of drought adaptation and was also manifested in A. gerardii from drier regions. Thus, drought-adapted ecotypes and cultivars might be able to maintain high photosynthetic productivity and protect photosystem II during dry periods. Conversely, the ecotypes and cultivar originating from areas with higher precipitation had lower leaf Chl and a lower Chl a/b ratio., K. L. Caudle, L. C. Johnson, S. G. Baer, B. R. Maricle., and Obsahuje bibliografii
Travinné ekosystémy jsou významnou součástí středoevropské krajiny. Polopřirozená travinná společenstva dnes tvoří v Evropě místa s vysokou biodiverzitou, jsou velmi náchylná k degradaci a k jejich efektivní ochraně je nutné znát vlivy různých typů managementu. Neodmyslitelnými obyvateli těchto ekosystémů jsou také zástupci rovnokřídlého hmyzu (Orthoptera), kteří zde hrají důležitou roli v potravní síti. Zároveň jsou vhodným indikátorem změn stanovištních podmínek, a to zejména struktury vegetace, čehož lze využít při zjišťování dopadů různých managementových opatření. Jedním z nejběžnějších a zároveň pro hmyz nejméně vhodných typů péče je dnes mechanizovaná seč. Nevhodná péče o travinné ekosystémy může ovlivňovat druhovou bohatost jak v měřítku lokálním tak i v měřítku krajiny. Snížení negativního dopadu seče ve prospěch biodiverzity lze docílit několika způsoby - např. zmírněnou intenzitou zásahu, a to posunutím nebo vynecháním první seče, nebo ponecháním neposečených ploch., Grasslands are an important part of the Central European landscape. Seminatural grasslands are considered to be biodiversity hotspots in Europe, with high conservation value. However, they are very unstable, and for their effective conservation it is necessary to know how different management systems affect the progression of the ecosystem. Orthopterans play an important role in the food web and they are also a good indicator of changes in habitat conditions, particularly in the vegetation structure, which can be used in determining the impact of different types of conservation management. Nowadays, one of the most common and least insect-friendly type of care is mechanized hay harvesting. Improper care can affect the species richness (both, on the local and landscape scale). The negative impact of mowing can be reduced in favour of biodiversity in several ways, as described (e.g., mitigating the intensity of the process by delaying or omitting the first mowing, or leaving uncut refuges)., and Oto Kaláb.