Urban Avocados – Radiant Heat – Aerosol Pollution
DATELINE SANTA BARBARA, CA 2012
This rather macabre Hass Avocado sighting is offered as being instructive about the effects of solar radiant heat on plant biota exposed to chronic urban aerosol fallout. This also reveals extreme environmental oddities which go unnoticed by the public and its agents.
The tree sits on the west side corner of large theater building. Sunlight falls on its canopy only about high noon when the sunlight is hottest. The canopy and crown is also exposed to wind and traffic dust coming from a busy street.
I had been watching this site for some time after I noticed necrotic leaves and immature fruit falling from the crown, and onto a grassy area. This area is also “tended to” and cleared of deadfall on a weekly basis by a hired landscaping crew.
These two Hass avocados, Persea americana (LAURACEAE, Laurel Family) fell to the grass in my presence.
Both fruits have blackened areas but the top face of the fruit on the right has a large blister, or smoldering welt. This heat absorbing black dome is about 6 mm. (.2″) thick which indicates a gain of mass. Some sort of strong, and sustaining, organic chemical reaction had to be taking place in order for this to happen.
This dome emitted considerable heat for many minutes after falling. To my flesh, it felt like being near dying embers of charcoal. Other photos will show other trees with thin crowns and blackened fruit that look like they have been chemically air baked.
The tree and its fruit are well watered and nourished — yet the exposed top canopy has lost fruit and leaves.
If this can happen in urban Southern California, it, or something similar can take place wherever flora or biota is exposed to the atmosphere containing hydrocarbon, VOC (volatile organic compounds), or traffic dust aerosol fallout. (Black ice fields, etc?)
The tree with blistered avocados is next the center white building in the background. A palm tree with a charcoal ember like (right side) trunk is in the foreground. Traffic dust and air currents go right to left of frame.
I have been around avocado trees and fruits (rotted, under/over ripe, etc.) for many years but had never seen anything like this take place.
This startling finding was made just days before I left SB, and after I had made my last appeal to civil government about the severity of air pollution on our landscape.
Photos: DT LANGE – CC 4.0 BY-NC
Related info, definitions, terminology:
Organic chemistry encompasses a very large number of compounds ( many millions ), and our previous discussion and illustrations have focused on their structural characteristics. Now that we can recognize these actors ( compounds ), we turn to the roles they are inclined to play in the scientific drama staged by the multitude of chemical reactions that define organic chemistry.
Reaction Conditions The environmental conditions, such as temperature, pressure, catalysts & solvent, under which a reaction progresses optimally. Catalysts are substances that accelerate the rate ( velocity ) of a chemical reaction without themselves being consumed or appearing as part of the reaction product.
Avocado, Hass, Persea americana
LAURACEAE, Laurel Family
The peel or rind (exocarp) consists of an epidermis with a cuticle, but in the warty fruits, the epidermis is replaced with cork from a cork cambium. The warts or bumps are airy zones in the cork called lenticels. Beneath this are several layers of cells, the innermost ones being sclerenchyma. The thick, green mesocarp is composed of millions of small parenchyma cells, some that are specialized for oil storage and others that have smaller amounts of oils. The endocarp consists of several layers of thin-walled cells.
Avocado oil is also isolated for many unusual products. It has a flash point of about 600 degree F and makes an excellent cooking oil (remember also its fatty acid composition!).
The first aim of the present work (study 1) was to analyze ethyl acetate, 70% acetone, and 70% methanol extracts of the peel, pulp, and seed from two avocado (Persea americana Mill.) varieties, namely, ‘Hass’ and ‘Fuerte’, for their phenolic composition and their in vitro antioxidant activity using the CUPRAC, DPPH, and ABTS assays. Their antimicrobial potential was also studied. Peels and seeds had higher amounts of phenolics and a more intense in vitro antioxidant potential than the pulp. Peels and seeds were rich in catechins, procyanidins, and hydroxycinnamic acids, whereas the pulp was particularly rich in hydroxybenzoic and hydroxycinnamic acids and procyanidins. The total phenolic content and antioxidant potential of avocado phenolics was affected by the extracting solvent and avocado variety. The avocado materials also displayed moderate antimicrobial effects against Gram-positive bacteria. Taking a step forward (study 2), extracts (70% acetone) from avocado peels and seeds were tested as inhibitors of oxidative reactions in meat patties. Avocado extracts protected meat lipids and proteins against oxidation with the effect on lipids being dependent on the avocado variety.