Thursday, September 17, 2009

Notoriously Promiscuous

A guidebook calls the Prickly Pear Cactus "notoriously promiscuous" because it often accepts pollen from species other than its own.   Flowers resulting from this promiscuity around Jerome, AZ, are colorfull and account for the yellow/red blossoms seen across Arizona in the Spring.

Note the insect at the lower left of the cactus's there feeding, watching, waiting for an encounter...just part of the diverse menagerie that keeps company with these soiled cactus doves of the desert. 

This environment doesn't take many chances, however...perhaps if the flower isn't fertilized notice the bud ready to open and start the process all over again.
Posted by Picasa

Labels: , , , , ,

Saturday, September 12, 2009

Birds, Bees, and Cactus Sex

It always fascinates me how plants maintain their niche in the desert environment by evolving to accept only certain pollinators and then only at particular times of the year. Bees, birds, bats and nearly everything small and mobile in the desert play a part in this ongoing drama.

The first hints come when you approach a flower and see that nearly always there is some form of life scrambling through the anthers and stamens. 

Flower petals and sepals are shaped to encourage and accept certain pollinators and reject others. Shape doesn't affect the spiders, for example, but it has a marked affect on whether bees, hummingbirds, bats and moths get in on the action. The Thurber gilia is a good example. Its pale lavender flowers are the wrong color to be noticed by hummingbirds and its tubes are too long for the hummingbirds to feed effectively. But this flower is an ideal food source for night fliers such as hawkmoths.

The evolutionary tricks are endless. The wild bean, for example, sports two-sided petals which serve as a convenient landing pad for bees that need to perch when they gather pollen. In contrast, the scarlet penstemon provides no such foothold and is a color that bees can't see...but alternately provides a perfect food source for hummingbirds that quickly distinguish reds and hover while feeding.

Cactus flowers, in particular, bloom when specific pollinators are seasonally abundant and active either nocturnally or during the daytime. Bats and hawkmoths aren't active during daylight hours but there are, nonetheless, cactus flowers open at night just for them. By opening for only a few hours early in the day, certain other flowers encourage bees...which have a well developed sense of arrive faithfully for nectar and pollen.

Probably the "largest" of these adapters is the saguaro cactus which has flowers that stay open for only about 36 hrs. (including the night following daytime bloom) and is pollinated by birds, bees and nectar-feeding bats. Timing for these desert giants is critical. Pollination and later seed dispersal is timed for the summer rains which follow shortly thereafter.

Pollination takes place either actively or passively. While some common pollinators are actively looking for pollen, others are seeking only nectar, pollinating passively as they search for the nectar. Flowers are selective, however, about which they allow.

Bees, for example, don't have a chance in hell of reaching the nectar in some flowers because they have short or non-existent tongues. Hawkmoths and certain butterflies, in contrast, have probosces which extend a full 1 1/2 to 2 in. to reach the nectar in other flowers such as columbine, gilia, and others.

What does all this go to show?...probably nothing of significance except that when you set out to take pictures of the sex organs of plants, you meet the strangest creatures. Sex and cameras have always gone together so I'm never surprised at what I see. Often it's only in photographic "post production", as the journals call it, 
when cactus flowers are enlarged to two or three times life-size that I see the bees, bugs and spiders that have crept into the camera's frame.

Labels: , , , ,

Wednesday, September 9, 2009

The Wisdom of Spines and Flowers

You wonder where they come from...the disparate elements of flowers and spines.

Alarmed queries often precede a visit to the desert. "Aren't you afraid of the snakes?" "What if you're pricked by a cactus?" "Are there scorpions?" All have spines...
The answer is usually a shrug because dangers are often unanticipated. In the initial stages of a journey just the flowers get our attention...and cactus flowers are among the most spectacular of their kind.

The desert is usually quiet except for the hum of bees, which have spines of their own. Flowers thrive, living in tranquility with the spines in a marked harmony of adaptation.

Cactus leaves have evolved into protective, water conserving spines...stems have  adapted as water reservoirs, and the flowers...the flowers attract their particular pollinators to ensure "appropriate" fertilization. 
Except for the occasional javelina or desert tortoise that grabs a bite of prickly pear, spines ensure that cactus flowers survive as the "least molested" of blossoms.
The desert, however, isn't generous to those who won't adapt to its regimen of lean necessity.  Cacti discovered long ago that only occasional water is necessary, that dry terrain and drought are a normal part of the environment, that predators are common, that excesses are rewarded with failure...and in this environment the desert hums along with its bees and flowers and spines in oft hidden tranquility.

It seems to know...if we won't adapt, if we lack an instinct for economy, we'll vanish...and the spines and flowers will look on with indifference.

The flowers will surely be here, but we may not see them.

Labels: , , ,

Tuesday, September 8, 2009

Looking for Spring in All the Wrong Places

Occasionally it's satisfying to imagine Spring is here even before the Winter rains have come and gone. These Opuntia (Prickly Pear) cactus flowers were growing last April in Bumble Bee, Arizona, a cross-roads where mine waste fights for recognition with junk cars and discarded drug paraphernalia.
But even though a friend opined that I had been in the sun too long because of some ideas I had, you often can get around the problem (bad ideas) with a broad-brimmed hat and SPF 30+ sun screen.  Cactus flowers love the sun and we go into their world with the bees, spiders and other pollinators if we want their photos.

Sometimes one of the most useful tools we can take with us on these ventures is a monopod with an attached ball head that steadies our cameras on the rocky slopes that cacti always seem to choose for home.  Don't tell anyone, but us seniors carry these things as much to get around as anything else.

One of my favorites is the Dusky Prickly Pear (above) which some guide books call "notoriously promiscuous" for coming to the party with tinges of red...a sure sign it has allowed a wayward pollinator around its stamens and stigma...and accepted exotic pollen into its genetic arsenal. 
Posted by Picasa

Labels: , , , , ,