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Sunscreen in plants


By Ranger Steve Mueller

By Ranger Steve Mueller

A red pigment called anthocyanin has been considered a sunscreen that protects plants from becoming sunburned, much like the sunscreens we use to protect us, from ultraviolet radiation (UV).

Look at newly emerging leaves from buds and notice the red color of the delicate tissues that have not yet “hardened.” When leaves expand from the bud, they are somewhat like a water balloon. They fill with water but the plant cannot build the necessary support tissues that rapidly. Feel newly expanded leaves to notice how delicate they are. The cellular tissues remain thin for days.

The leaves of trees and shrubs expand rapidly but it takes much longer to reinforce cells with cellulose and other strengthening tissues. The first line of defense to protect delicate tissues from UV radiation would reasonably be found in the protective outer cell layer called the epidermis. This layer lacks the green chlorophylls that make leaves green and it also has a low concentration of anthocyanin. Anthocyanin is more abundant deeper in leaf tissues called palisade cells, where vertical rows of cells stand next to each other and circulate green chloroplasts to capture sun energy. It also is more abundant in photosynthetic cells beneath the palisade cells know as spongy mesophyll cells. Studies are trying to understand the mystery UV protection.

Think of the palisade cells like a series of farm silos packed closely together to fill a checkerboard. They are tall and slim. Imagine each silo filled with water and beach balls. The balls represent the chloroplasts that form a moving loop inside silo like an internal Ferris wheel. The chloroplasts are like seats on the Ferris wheel following others as they rise to the top and circulate back down to bottom. The spongy mesophyll cells below the palisade cells are more globular in water filled spaces between cells.

UV can cause damage to DNA in the cells of the two layers, just like damage can cause cancer in our skin tissues. Anthocyanin filters radiation to varying degrees and helps protect plants. Melanin in our skin serves that function and is built when our skin is exposed to UV and makes us tan.

Shade tolerant plants in the understory of forests are protected from intense sun radiation by the forest canopy. When trees are clear cut, the ground plants are suddenly exposed to UV and respond. They produce large quantities of anthocyanin and become intensely red. Unfortunately, it is not adequate to save them and most succumb to sunburn. Plants adapted to tolerate open sunny nature niches colonize the new sunny habitat. When you see a clear-cut forest, stop to notice how red the ground plants become when exposed.

Explore with family members to notice new growth on dogwood shrubs, maples, sassafras, oaks, and cherries. Choose any tree or shrub and feel how soft and delicate new tissues are and that they are pigmented red until they harden and feel sturdy. It is universal that the new tissues concentrate anthocyanin. The water-soluble pigment has other functions also but it plays a role as protective sunscreen. Phenolic acids in corn and other crops are UV-absorbing compounds so anthocyanin is not the only sunscreen. More mysteries are waiting discovery.

Declining levels of ozone in the upper atmosphere have generated concern because more UV radiation is entering the lower atmosphere where we live. In our latitudes, UV has risen by 3 to 5 percent in recent decades. Closer to the poles it has risen 6 to 8 percent. Increased skin cancer in people is occurring. People are not the only species impacted by UV radiation but we tend to think we are isolated from nature niches. That is not now nature works. What happens to plants happens to people. We do not live alone and sustainable care for other life is essential for our own health. Food and forest productivity depend on how we care for ozone layers.

Natural history questions or topic suggestions can be directed to Ranger Steve (Mueller) at odybrook@chartermi.net Ody Brook Nature Sanctuary, 13010 Northland Dr, Cedar Springs, MI 49319-8433. 616-696-1753.

Posted in Ranger Steve's Nature NicheComments Off

Summer garden glory without the weeding and watering


Radically Reduce Garden Maintenance

(BPT) – Summer can be tough on gardens. In what should be their glory days, many gardens suffer from neglect. Long weekends and summer vacations leave yards untended, while summer heat is an excuse for putting off chores. But it doesn’t have to be that way. It’s possible to have both a glorious well-maintained garden and time for fun in the sun by taking some smart gardening steps now.

Here’s a quick list of pro-active steps from the experts at preen.com to transform a yard or garden from needy-and-greedy to lean-and-green by reducing watering and weeding needs all season.

* Choose better places for better plants – Many plant experts insist that 90 percent of garden problems would disappear if gardeners put the right plants in the right places. But, sometimes it’s the planting place itself that needs adjustment. For example, a hot, dry, exposed setting is brutal on most plant selections. Why not completely rethink a spot like this? To alter the heat-and-light dynamic, introduce a small shade tree to serve as the anchor of a new easy-care landscape bed. Add a supporting cast of drought-tolerant shrubs and perennials. With better places for better plants, long-term maintenance can be a breeze.

* Whack weeding – Weeding consumes more time in the garden than anything else, except watering, according to a National Gardening Association survey. Covering garden beds with a 3-inch layer of mulch will greatly reduce the need to weed and water, while making everything look tidy too. Mulch retains soil moisture and denies weed seeds the light they need to sprout. Top off mulch with a sprinkling of a pre-emergent such as Preen to stop weed seeds from growing in mulch and garden soil for up to three or four months. For a one-step solution that creates a six-month weed-fighting barrier, try Preen Mulch Plus, a natural shredded-wood mulch with added pre-emergent weed preventers already mixed in.

* Beef up the border patrol – Sharply-defined edges around garden beds add visual appeal to any property. They also make maintenance easier by creating a firm demarcation between beds and lawns to keep out invasive perennial weeds, including nasty creepers that can’t be prevented by other means. Dig a shallow 8-inch wide trench surrounding garden beds, then cover it with 3 inches of mulch; or install a barrier-style perimeter edging of metal, stone, rubber or wood.

* Banish fainting spells – When it comes to water-retentive container plantings, think fewer and bigger. Don’t dot decks, doorways and patios with fussy little pots. Small containers look insignificant and dry out fast, subjecting parched plants to repeated bouts of stress from fainting spells. Larger containers allow for more dramatic plant groupings and plenty of healthy root room, plus retain important soil moisture.

* Try tick-tock watering – Gardens need less water than many think, thriving on as little as 1 inch of water per week whether it’s delivered by rain, drip irrigation, sprinklers or a hand-held hose. To save time watering all season and prepare a garden to get through extended dry spells, add programmable water timers to water spigots and hose systems. Even inexpensive timers can deliver water to suit particular plant and climate needs. Early morning watering is best. Midday sun can burn wet leaves. Evening watering can lead to plant ailments and mildew.

Don’t spend the summer constantly weeding, watering and struggling to keep up with garden chores. Put your garden on a path to self-sufficiency. Then focus on fun in the sun, whether you’re on vacation or in your own backyard.

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