Arquivos de periódicos de maio 2020

12 de maio de 2020

A geographical comparison of Aloe maculata

1st observation:
Metamorphosed Cape Sandstone ledge - 1680 masl
Specimen features
*Twice to much-branched inflorescence
*Inflorescence >1 meter
*Leaves in basal rosette, becoming slightly caulescent. Withering at tips
*Growing in scattered colony of 50+ plants

2nd observation:
Cape Sandstone slopes, undulating - KZN province - 1565 masl
Specimen features
*Much-branched inflorescence
*Inflorescence >1.5 meters
*Leaves basal rosette, with variable white striations (under and upperside), withering at tips
*Growing in high density colony of >200 plants

3rd observation:
Cape Sandstone plateau - KZN province - 1340 masl
Specimen features
*Twice branched inflorescence
*Inflorescence > 1 meter
*Leaves in basal rosette, with variable white striations (under and upperside), withering at tips
*Growing in scattered colony of +- 40-50 plants

4th observation
Cape Sandstone ledge - Cape Peninsula, Western Cape Province - 210 masl
Specimen features
*Unbranched inflorescence
*Inflorescence <1 meter
*Leaves basal rosette, with variable white striations (under and upperside), withering at tips
*Growing singly or in very sparse colonies of +- 10 plants

Notes:

There seems to be a positive correlation between an increase in altitude of the habitat and an increase in the number of Aloe's in the population/ colony
Furthermore, there seems to also be a positive correlation between an increase in altitude and the height and degree of inflorescence branching, among a few other characteristics such as leaf shape (lower altitude = broader based, oval shaped leaves)
Both these correlations could be the result of: A) A gradual change in the phyto-communal makeup of the habitats with an increase in altitude (shorter, less bushy, graminoid community more prominent with increasing altitude, offering less competition). B) Slight differences in the geology, soil depth and drainage of the habitat (1st observation - medium grained sandstone, uniform deposition. 2nd observation - fine grained, impermeable sandstone, more exposed and uneven. 3rd observation - Very consolidated sandstone, undulating and slightly metamorphosed by granite), or more subtle changes in temperature as a result of increasing/ decreasing altitude C) Changes in the number and reliability of pollinators, possibly as a result of point (a)

The last point is less likely, as one would expect a higher, more branched inflorescence offering nectar rewards in greater number as the habitat becomes more bushy and the above ground leaf/ canopy coverage increases. However, it is possible that Aloe communities in higher altitude area's take advantage of less competition from dense-growing, caulescent plants by producing more branches and more flowers with a more diluted reserve of nectar thereby encouraging greater genetic dispersal in these open habitats. This remains to be confirmed

Posted on 12 de maio de 2020, 08:30 PM by anthonywalton anthonywalton | 3 observações | 0 comentários | Deixar um comentário

Genus comparison: Plectranthus and Stachys (Lamiaceae)

Plectranthus (Spurflower)
*2 spur-like appendages, erect/ semi-erect, adjoined to the rim of the upper corolla tube hood
*Lack a leafy calyx at base of corolla tube

Stachys (Hedgenettles)
*Lack any appendages on the side of the upper corolla hood. Outer lower tepal lobes sometimes shrunk, superficially resemble spurs but aren't
*Very leafy calyx, immediately subtending at the base of the tube

Posted on 12 de maio de 2020, 10:45 PM by anthonywalton anthonywalton | 2 observações | 0 comentários | Deixar um comentário

23 de maio de 2020

Life stage and flowering of Stachys aethiopica

1st observation:
Peak of basalt, Karoo-dolerite buttress, KZN
Specimen features
*Plant in flower
*Small, tufted herb, very short, with a basal coverage of only 5 -10 cm's (Primary growth completed?)
*No sign of secondary growth (elongation)
*Plant growing in exposed, fire-prone area

2nd observation:
Rocky, undulating slopes, Cape Sandstone, Western Cape
Specimen features
*Plant in flower
*Plant > 30 cm in height, with well defined internodes. Leaves and flowers in well-defined whorls and plant has a scrambling habit, depending partially on other plants in the scrub for support.
*Plant has completed secondary growth
*Plant growing under rocky ledge, surrounded by scrub. Unexposed area but still fire prone

Notes:

This species flowers both before and after the secondary growth phase has been completed. Variables to consider in this instance would be temp and climate differences (big difference in altitudes between 2 obs), as well as species response to habitat physiognomy (1st ob - open grassland; 2nd ob - Fynbos scrub). However, it is nevertheless interesting to note that completion of secondary growth is not always a pre-condition to flowering. Furthermore, it is interesting to note that in some plants, primary growth involves thickening and leaf development only at the base (growth of basal cover), whilst secondary growth entails an elongation of the internodes and defining of the plants flower and leaf arrangement.

Posted on 23 de maio de 2020, 11:37 AM by anthonywalton anthonywalton | 2 observações | 0 comentários | Deixar um comentário