February 19, 2017

ARIZONA : SAGUARO - SKELETONS / flowers / spines / silhouette

ARIZONA : SAGUARO - Saguaro Skeletons
Skeletons


Saguaro Cactus Skeleton, Saguaro National Park, Tucson, Arizona
The roots of a saguaro grow out from the plant in a radial fashion, several inches under the ground. During a heavy rain, a saguaro will absorb as much water as its root system allows.

To accomodate this potentially large influx of water, the pleats allow the flesh to soak up water, expanding like an accordion. Conversely, when the desert is dry, the saguaro uses its stored water and the pleats contract.

Because the majority of a saguaro is made up of water, an adult plant may weigh 6 tons or more. This tremendous weight is supported by a circular skeleton of inter-connected, woody ribs. The number of ribs inside the plant correspond to the number of pleats on the outside of the plant. As the saguaro grows, the ribs will occasionally fork and the corresponding pleat will also fork at the same place.

Sometimes saguaros have the chance to soak up a larger than usual amount of water - such as after a large summer rainstorm. The ground can become very soft after such a storm and with the added weight of the new water, the heavy cactus sometimes fall over or lose an arm.

National Park Service






ARIZONA : SAGUARO - Saguaro flowers
Flowers


Flowers appear in April through June. They are white and open well after sunset and close in mid-afternoon. They continue to produce nectar after sunrise. Flowers are self-incompatible, thus require cross-pollination. Large quantities of pollen are required for complete pollination because many ovules are present. This pollen is produced by the extremely numerous stamens which in one case totaled 3,482 in a single flower. A well-pollinated fruit contains several thousand tiny seeds. Saguaros have a redundant pollination system, i.e. full fruit set is possible even if only a fraction of the pollinating species are present.


Saguaro flowers, Saguaro National Park, Tucson, Arizona


Main pollinators are honey bees, bats, and white-winged doves. In most years, diurnal visitors are the main contributors for fruit, most of them honey bees. Other diurnal pollinators are birds such as Costa's hummingbird, the black-chinned hummingbird, the broad-billed hummingbird, the hooded oriole, Scott's oriole, the Gila woodpecker, the gilded flicker, the verdin, and the house finch.

The main nocturnal pollinator is the lesser long-nosed bat, feeding on the nectar. A number of floral characteristics are geared toward bat pollination: nocturnal opening of the flowers, nocturnal maturation of pollen, very rich nectar, position high above ground, durable blooms that can withstand a bat's weight, and fragrance emitted at night. Further, the amino acids in the pollen appear to help sustain lactation in bats.
Wikipedia

ARIZONA : SAGUARO - Saguaro spines
Spines


A Close up of Saguaro Cactus spines, Saguaro National Park, Tucson, Arizona


The spines on a saguaro, less than two meters in height, rapidly grow up to a millimeter per day. When held up to the light or bisected, alternating light and dark bands transverse to the long axis of spines can be seen. These transverse bands have been correlated to daily growth. In columnar cacti, spines almost always grow in areoles which originate at the apex of the plant. A spine stops growing in its first season. Areoles are moved to the side and the apex continues to grow upwards. Thus, older spines are towards the base of a columnar cactus and newer spines are near the apex. Studies are underway to examine the relationship of carbon and oxygen isotope ratios in the tissues of spines of an individual to its climate and photosynthetic history (acanthochronology).


ARIZONA : SAGUARO - Saguaro sunset silhouette
Silhouette


Saguaro cactus in silhouette at sunset, Saguaro National Park, Tucson, Arizona


State of Sonora, and the Whipple Mountains and Imperial County areas of California. The saguaro blossom is the state wildflower of Arizona. Its scientific name is given in honor of Andrew Carnegie. In 1994, Saguaro National Park, near Tucson, Arizona, was designated to help protect this species and its habitat. It is the only US national park devoted to a particular plant species.

Growth

Saguaros have a relatively long lifespan. They may grow their first side arm any time from 75–100 years of age, but some never grow one at all. A saguaro without arms is called a spear.

The arms are grown to increase the plant's reproductive capacity (more apices lead to more flowers and fruit). The growth rate of saguaros is strongly dependent on precipitation; saguaros in drier western Arizona grow only half as fast as those in and around Tucson, Arizona. Saguaros grow slowly from seed, never from cuttings. Specimens may live for more than 150 years and grow to be over 40 ft tall. The largest known living saguaro is the Champion Saguaro growing in Maricopa County, Arizona, and is 13.8 m (45.3 ft) tall with a girth of 3.1 m (10 ft). The tallest saguaro ever measured was an armless specimen found near Cave Creek, Arizona; it measured 78 feet (24 m) tall before it blew over in a windstorm in 1986.

Saguaros soak up the rainwater and visibly expand. They conserve the water and slowly consume it.


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