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Abstract

Southern California has a Mediterranean climate with wet winters and hot dry summers. This type of environment is associated with irregular temperature patterns and rainfall, which can be unpredictable. Unpredictable environments, can threaten the germination and survival of plants like Centaurea melitensis. To ensure germination and survival under unpredictable environmental conditions, some plants may develop characteristic structures like cleistogamous flower heads, and in some cases they will develop heteromorphic achenes. Morphological differences between peripheral and center achenes may indicate variable responses to temperature. Additionally, unpredictable environmental conditions may lead to differences in the number of peripheral to center achenes in each head type. This study was designed to investigate differences in germination of peripheral and center achene's of each head type CH (Chasmogamous), iCL (Initial cleistogamous) and fCL (Final cleistogamous) when subjected to constant temperatures 5C, 10C, 15C, 23.5C and 30C. Differences in achene ratios (central to peripheral) and persistence were also investigated. A total of 400 achenes per achene type was used. Twenty achenes were placed in a petri dish filled with 6 ml of distilled water; the plates were incubated at one of five temperatures for seven days. The number of achenes (central to peripheral) remaining in the flower head three months post dispersal was documented. The results indicate that Centaurea melitensis was significantly affected by temperature. A fraction of the achenes remain in the flower head until early fall. Ratio differences in peripheral and center achenes may be a reflection of unstable environmental conditions.

DOI

10.5642/lux.201303.01

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