July 2017

The Botanical Garden of the Hebrew University on Mount Scopus – a phytogeographical-phytosociological garden

Uri Roseberg agron@netvision.net.il

Keywords: Otto Warburg, Menachm Ussishskin, Alexander Eig, Tuvia Kushnir, Jerusalem, Michael Zohary, Nicanor (Seleucid general), Naomi Feinbrun-Dothan, Leon Pinsker, flora Palaestina

The botanical garden of the Hebrew University on Mount Scopus was established in 1931. It also embraces thousands of years of archaeological findings, and diverse historical, cultural, and Zionsit memories. However, it is first and foremost the first botanical and scientific garden of its kind in Israel, as a garden of the wild plants of Eretz Yisrael, and among the first ecological gardens in the world.  In this article I shall briefly survey the history of the garden, focusing primarily on its botanical aspects.

Full Hebrew version

The Russian Knapweed – a new plant in Israel

Ran Lotan, collector of seeds for the gene bank. ranlotan@walla.co.il
Zalman Baumwol
, amateur botanist. zalman;en@gmail.com
Ori Fragman-Sapir, Scientific director of the University Botanical Garden, Jerusalem. fragman@botanic.co.il

Keywords: damp habitat , Centaurea, Asteraceae, endangered species, fertilized habitats, alien plant, invasive plant, northern Golan Heights, distribution zone

The Russian Knapweed (Rhaponticum repens, Asteraceae)  was first found in Israel on Mt. Hermonit, in the Golan Heights. The plant is similar to species of Centaury and in the past was associated with a particular species of Centaury. However, today it is identified as a species in a separate genus. This is a widespread species in temperate zones in Southern Asia, in fertilized or damp habitats. In other areas in the world it is an invasive species.  In the article the description of the plant, its taxonomic status, its distribution and ecology are presented. The question whether this is a rare and endangered species, or an alien species that is liable to become an invasive species in Israel, is discussed.

 Full hebrew version

From what distance does a bee see a flower? The maximum exposure distance of natural flowers by bumble bees

Gidi Neeman, The Biology and Environment Department, Haifa University – Oranim. gneeman@gmail.com
Rina Neeman, Moshav Amirim. rina.nem@gmail.com

Keywords: Bombus bee, minimal visual angle, detection distance, green contrast, contour line, vision, flower surface, flowering and pollination

Plants use visual signals to attract pollinators and direct them to their flowers. Visual capabilities of bees have been extensively studied mostly using artificial paper models. However, there is no empirical determination of the maximal detection distance (MDD) or minimal subtended visual angle (MSVA) of real flowers. Using a six armed radial maze, we tested MDD and MSVA of 12 types of natural and manipulated real flowers by bumble bee (Bombus terrestris) workers. Bees were initially trained to obtain sugar solution at target flowers that were presented at close range on a mobile divider at the back of one of the six arms. Bees were individually marked and tested. For bees that passed the short range test, we gradually increased the distance of the target flower, until the number of successful choices reached chance level, indicating that they could not see the target flowers. The results show that MSVA of flowers is correlated with flower diameter but not with MDD. The variation in MDD to natural flowers by bumble bee workers can be best predicted by: MDD = flower coloured area / (contour line * green contrast). Contour line length determines flower dissectedness. Full circular flowers can be detected from longer distance than dissected flowers with identical diameter. We hypothesize that dissected flower shapes might be compensated by their higher attractiveness for bees. Empirical determination of real flower MDD and MSVA is important for studying bee foraging behaviour, pollinator induced evolution of flower traits and validation of neurophysiological visual models.

Full Hebrew version