Living Fossils Lose Status
Studies done at Harvard and UC Berkeley, by a scientist now at the Royal Botanic Gardens in Sydney, have shown that our present-day cycads evolved fifty million years after the dinosaurs were gone. That makes the earliest of our cycad species only about twelve million years old—not living remnants of the ancient plants of the Jurassic period as once thought. Two-thirds of the 300 known species from around the world were examined using a technique known as the molecular clock. The accumulation of DNA mutations coding for certain proteins within a group of plants reveal how much time has passed since the time of a common ancestor. It has been suggested that there must have been an environmental trigger twelve million years ago that caused all the present groups of cycads to be synchronous in their speciation away from an original ancient lineage.
Science Express, October 20, 2011
Seeds of some plants can remain viable for hundreds of years under proper storage conditions; others last only a couple of decades. Researchers at the Millennium Seed Bank at Kew Gardens, along with their international research partners, have shown that seeds of alpine plants are shorter lived than their lowland relatives. Special care will be required to set up appropriate monitoring intervals to test seed viability for these species. The Millennium Seed Bank has acquired seed from 24,000 species of plants, representing ten percent of the world’s dryland plants, as of 2010. Plants from dryland areas are among the primary foci of the initial seed collection effort. It is expected that, by 2020, the project will have collected twenty-five percent of the world’s dryland plant species. The underground storage vault is large enough to hold thirty, tightly packed, double-decker buses.
Annals of Botany 107 (2011): 171-179 and The Atlantic, Sept 23, 2011
No Digging Required
Planting large swaths of tulips does not have to be back-breaking work. Cornell University’s bulb guru, Dr William Miller, experimented with various planting depths to determine the success of flowering and perennialization of tulips in a USDA Zone 5 area of upstate New York. He found that tilling the soil a few inches deep, placing bulbs on the soil surface, and covering them with several inches of mulch (to be replenished annually) was successful and, perhaps, even preferable to burying the bulbs six to eight inches deep, as retail packages recommend. Although only tulips were used in the study, it is suspected that other bulbs would be similarly successful with this method.
Flower Bulb Research Newsletter, Published by Anthos, Royal Dutch Trade Association for Nurserystock and Flowerbulbs, July 2011, and the Cornell Chronicle, Oct 12, 2011
Nature vs Nurture
It is reasonable to expect that genetically identical trees would respond similarly to drought conditions, but there has long been suspicion that a “nursery effect” might exist. Researchers in Canada wanted to see how three different clonal lines of hybrid poplar trees, originating from nurseries in different climatic conditions in different provinces, would respond when brought together under the same controlled climatic conditions, with some eventually subjected to drought stress. After collecting the three different clonal lines, each line gathered from two different provinces, groups of progeny from each location were grown in a climate-controlled greenhouse at the University of Toronto for at least nine weeks. Half of the plants from each location were then subjected to drought conditions. What researchers found was that in two of the three clonal lines, genetically identical trees responded differently depending upon the nursery and climate from which they came. The two “older” hybrid lines, showed the greatest “nursery effect.”
The conclusion is that epigenetic changes (modifications in how the DNA is read, not changes to the DNA code) occur over time within clonal lines, influenced by various pressures, such as water availability, pests, or soil conditions, that, in effect, provide a kind of genetic diversity dependent upon the geographic origin of the clone. These epigenetic changes grow more persistent over time, as long as the clone remains in the same habitat. The changes are then functionally recorded in the molecular memory, even if the plant’s progeny are moved to a new geographical location. Aside from ecologic implications of clonal species being able to adapt epigenetically (or not) to varying environmental conditions, these findings are important to foresters who may be sourcing trees, grown in different climatic conditions, that might respond differently to changing growing conditions—despite the genetic identity of the trees.
Proceedings of the National Academy of Sciences, vol. 108 no. 30: 12521-12526
Pine Needles and Soil Acidity
It is widely believed that, if your soil is not acidic enough to grow blueberries and azaleas, you can increase the acidity by mulching or amending with pine needles. Various studies over the years have attempted to address this notion, but good data is not easy to find. The general information bulletins provided to the public by university extension offices in many states profess that pine needle mulch is “good to use around acid-loving plants;” others make no claims about soil pH manipulation with pine needles, instead proclaiming the many other virtues of a needle mulch. One fairly recent study, done by the Agricultural Research Service branch of the USDA, found that needles of loblolly pine (Pinus taeda), often called pine straw, incorporated into topsoil did not, over a twelve-month period, reduce the pH of the soil.
ARS Research Paper: “Effect of Pine Bark, Pine Straw, and Red Oak Wood Mulches on Soil pH,” by David Burner