Plants with seed reserves that open like a star

Published: November 15th, 2007 | Updated: 17/01/15

[Anvillea garcinii] (Fig. 3.2.1) is a dwarf shrub of the extreme desert which has pretty inflorescences that open in an interesting way when wet. When collecting ripe heads one must be wary of the spiny nature of the dry bracts. Figure 3.2.2 may assist us in displaying a large group of plants having “surprising advantages.” The seeds are hidden among the plant parts in a reservoir which looks like a ball or an egg close to the soil. After wetting, the bracts or ovary walls open and appear as a star-like plant-part with seeds at its center.

Fig. 3.2.1: Anvillea garcinii.

Fig. 3.2.2: A schematic presentation of a plant opening after wetting of the fruit. a. A dry plant, b. After wetting, c. A tissue elongating greatly upon wetting, d. A tissue elongating slightly upon wetting, e. Seeds or achenes, f. Bracts of a flowering head or valves of a capsule.

[Asteriscus hierochunticus]

When coming upon [Asteriscus] in the desert (Fig. 3.2.3) one may think that he has found a lignified gray mushroom (Fig. 3.2.4). Plants of this species that have developed in a site with a small quantity of water, develop into specimens with only one flowering head. Plants having a relatively high quantity of available water develop branches of several orders (Fig. 3.2.5). Wetting of the dry plants, as under a rainfall shower, brings about opening of the involucral bracts and exposure of the center to the rain drops. (Fig. 3.2.6). This mechanism should be considered as a “rain-gauge” as well. The rain drops detach the bracts covering the achenes and when the latter are exposed, their pappus opens and assists their dispersal by wind. The achenes are either wind-borne or splashed out of the opened head by rain drops and are ready to germinate.

Fig. 3.2.3: Asteriscus hierochunticus – an old gray specimen, with one black head which was wetted, and its present second-year offsprings.

A shower that is strong enough to splash out the achenes may sufficiently wet the soil, thus enabling germination and seedling establishment. The advantage for the visitor in the desert is the 5 minutes opening time (even faster in hot water) and the easy handling and preservation of this “souvenir.” To those who think of the plant’s anatomical features: the fibers that are active in the movement are situated in the inner side of the involucral bracts (as shown in Fig. 3.2.2). [Asteriscus aquaticus], growing in the moister part of the country and confined to clayey soils and to dwarf shrub communities, resembles [“Asteriscus hierochunticus” A. hierochunticus], but has longer stems. To see other species from the same family ([http://flora.huji.ac.il/browse.asp?action=browse&group=1 Asteraceae]) use the links to: [Cichorium endivia] and [Filago contracta]. Of the [http://flora.huji.ac.il/browse.asp?action=browse&group=24 Apiaceae] [Ammi visnaga] has large umbels which open slowly when wetted in winter.

Fig. 3.2.4: “Mushrooms” of Asteriscus of previous years which provided the seeds for the present year flowering specimens.

Fig. 3.2.5: Asteriscus which developed in a site where up to third order flowering head could develop. Often, water is sufficient for production of only first order heads. I – first order head, II – second order head, III – third order head.

Fig. 3.2.6: 5 minutes after wetting, involucral bracts open. At the capitulum center a cake-like (something!) made of bracts, each with a white line and a hidden axillar achene.

Fig. 3.2.7: After opening of the involucral bracts of the capitulum, raindrops hit the bracts with white lines and their axillar achenes become detached. The achene’s pappus opens and pushes the achene upwards. Pappous achenes become wind-borne or splashed with additional rain drops.

[Opophytum forsskalii]

This plant may be regarded as a “winner” because of several features. This is the plant most resistant to soil salinity in extremely dry areas. It flourishes in rainy years when the ground is leached enough in saline places in the Dead Sea area and the Arava. When young, the plant looks like a water reservoir built up from green sausages linked together in an imaginary statue by an ultra-modern artist. After blooming, the green pigments in the plant begin to deteriorate and the plants become yellow (Fig. 3.2.9).

The dry plant is fragile and when its dry fruits are wetted, they open in 1-2 minutes (Figs. 3.2.10 and 3.2.11). The small brown-black seeds become exposed to the rain, ready to be splashed to the ground by rain drops, and develop accordingly. Literary records and stories “from father to son” in the Negev, claim that the Bedouin used the seeds of this plant to prepare “black desert bread”. The dry plants were collected and put into large water jugs (or pitchers). Seeds were collected from the jug’s bottom, dried, and ground, to prepare the bread. The Bedouin who told me about it preferred to regard this bread as a means of survival and not as a kind of delicacy. To see other species from the same family ([Aizoaceae]) use the links to: [Aizoon hispanicum], [Mesembryanthemum nodiflorum] and [“Mesembryanthemum crystallinum” M. crystallinum].

Fig. 3.2.8: Opophytum forsskalii – A young plant which stored a large quantity of water from the soil while its salts were diluted in winter.

Fig. 3.2.9: Flowering. The chlorophyll in older leaves starts to disappear, thus exposing yellow pigments.

Fig. 3.2.10: Opophytum forsskalii – a. Dry , b. Moist, c. After wetting.

Fig. 3.2.11: Opophytum forsskalii – a. Dry , b. After wetting.