Category Archives: Plant Metabolism & Photosynthesis

Following the Vascular Trail: The Path of Water from Soil to Atmosphere

Oak Savanna on a dry hilltop in Shiloh Ranch Regional Park, Sonoma County, California.

Oak Savanna on a dry hilltop in Shiloh Ranch Regional Park, Sonoma County, California.

Second in the Water Series

Try to imagine life without water….No matter how dry it may seem to be here, the soil cracked open in supplication, the lawns toasted and tan, Rhododendrons with their leaves curled and burnt along their margins, Vine and Japanese Maples, their leaves crisped blowing down curbs in late summer’s heat, there is water…everywhere, locked deeply in tissues, bound tightly to soil particles. Like most things, there are no absolutes with water. It is not simply here then gone, but on a continuum of availability. Biological scientists and agronomists will often speak of ‘dry weight’ when looking at growth trying to minimize the variability of water weight in living organisms. They bake the subject in autoclaves reducing water weight to zero without igniting and burning the carbon and more ‘solid’ structure to ash. There is water throughout the structure of plants, hydrating their cells, making possible the many processes at work within them. There is water in the atmosphere even on a blistering hot and clear day in the form of vapor effecting everything from the Evapotranspiration Rate, (ET), to how hot or cold we may feel beyond what the thermometer reads; and there is water in the soil though our plants be wilting or dead of desiccation, and it effectively sucks the moisture from our skin when we work bare handed in it. Water is everywhere even in the dry periods within the desert and, nature is okay with that and has in fact adjusted to it. Our gardens, however, are anomalies we’ve created. We are invested in them and as gardeners we do what we can to assure their survival, and more, their success! Continue reading


On Planting in Drought Conditions: the Relationship of Roots, Water and Soil

I had a novice gardening friend ask me the other day about planting the dry, xeric, part of her yard.  Many of you know how abnormally dry and warm a spring/June it’s been here.  Those of us with gardens requiring routine irrigation started a few weeks ago and we’re expected to be heading into an extended hot/dry period over the next 8 or 9 days with temps over 90 F. (While it is not unusual to experience 80+ deg. days here in June it is unusual when you look at our overall pattern this spring.  Remember that we can also have Junes where it is common not to get out of the 60’s with our famous Portland drizzle day after day while we wait for July and the ‘beginning’ of summer.)  She was anxious to get her new plants in the ground and was asking me about amendments as the soil was baked and hard…. Continue reading

Hiking in Phoenix’s South Mountain Preserve

A Saguaro along the Bajada Trail looking toward the Estrella Mountains in the distance to the west and Ma Ha Tauk Ridge above me to the right.

A Saguaro along the Bajada Trail looking toward the Estrella Mountains in the distance to the west and Ma Ha Tauk Range above me to the right.

(This will be one of several entries describing hikes, botanical gardens and arboretum I visited in southern Arizona this April, 2015.)

Today Julie has work to do (She’s on a buying trip and I tagged along!) so I’m going out, down to the Phoenix South Mountain Preserve to hike a loop on the Bajada (the incline at the base of a mountain formed by the erosion of the mountain) and Alta (or high) trails. The Preserve, at over 16,000 acres is the largest municipal park in the US (Portland’s Forest Park pales at 5,172 acres.) I began my hike going the ‘wrong’ way on the Max Delta Trail having incorrectly read the directions so I added an unnecessary mile by the time I figured it out. The Bajada Trail climbs only 40’ but it constantly wends its way around rocky barriers and down and back up washes filled with tumbled granites…. The hike and region lies within the Sonoran Desert Scrub region, Sonoran, because the majority of the plants are sub-tropical in origin and are associated with the plants of Mexico’s Sierra Madre Occidental and Baja Region, not plants from the Rocky Mountain Plateau. The Salt River, that ‘flows’ south and west through Phoenix, is the northern boundary of this region, where the area becomes transitional as it gains elevation climbing to the Verde River and Mogollon Rim. Okay, too much. Continue reading

Photosynthesis Types: C3, C4 and CAM a simple overview

If you’re curious I found a relatively simple, not too technical, overview on-line titled: 

Photosynthesis – An Overview

There are 3 basic types of photosynthesis:  C3, C4, and CAM.  Each has advantages and disadvantages for plants living in different habitats.

Check it out at:

The bulk of plant species, around 90%, utilize C3, while C4 plants comprise 3% (7,600) of all plant species, but account for 30% of terrestrial carbon fixation.  46% of the Grass Family are C4s, including Corn, Sugar Cane, Millet and Sorgum.  They make up 61% of all C4 plants.  Most C4s are monocots, obviously.  Among the dicots are many species from the Aster, Brassica, Amaranth and Euphorbia families.

C4 plants have a competitive advantage over C3 plants when grown under higher temperature conditions, 30+ C (C4 plants are concentrated in the tropics and sub-tropics where temps are higher), with lower available nitrogen and drought.  With moderate temperatures, available N and water, C3 has the advantage.  CAM have the greatest advantage under desert conditions.

Among other things scientists are trying to engineer Rice, a C3 plant, into a C4 plant, increasing yields and lowering their water requirements for growth.  Rice is the most commonly consumed food plant in the world.

Crassulacean Miracles

Some of my CAM plants: back, Agave colorata, A. americana Medio-Picta; middle, Hechtia 'Texas Red' w/ Sedum 'Anglina', Agave gentryi 'Jaws', Puya venusta, Aloe (?); front, Puya chiliense, Dyckia 'Big Red', Senecio mandraliscae and Agave parryi 'Cream Sickle'

Some of my CAM plants: back, Agave colorata, A. americana Medio-Picta; middle, Hechtia texensis’ Big Red’ w/ Sedum ‘Angelina’, Agave gentryi ‘Jaws’, Puya venusta, Aloe (?); front, Puya chiliensis, Dyckia ‘Red Devil’, Senecio mandraliscae and Agave parryi ‘Cream Spike’

Plants for me are little windows into the working of the world. Beautiful, exotic, grand or seemingly simplistic, perfectly attuned to their place. We are simple animals ourselves our attentions grabbed and later lost by what shimmers and glitters in our minds for a moment. We look, but only partially see. Each plant is an opportunity, maybe a lesson and later forgotten by most of us, unaware that there is anything there to learn beyond our initial attraction to the physical plant itself. The unrolling of a leaf of Liriodendron, like a flag, happening 10 thousand times on one tree, each year across the span of its years, for generations for millions of years. The perfectly memorized pattern of the single enormous leaf of an Amorphophallus as it stretches up out of its corm, fully formed, each leaflet revealed as a piece, entire, not expanding through a growing tip, adding tissue, but revealing itself wholly if we watch. Each plant a miracle to all but the blind.

I was reading an article on UBC’s botany photo of the day site, on Crassula ovata (Jade Plant). It is one of the most common of the Crassula species in South Africa growing on sandy loam soils, with around 12”-18” of rain as part of what some call the ‘Albany Thicket’. Continue reading