Exam #1 EFB 437 – Propagation February 13, 2019

Name

It’s early September and you want to germinate fifty or so seed you’ve removed from the shiny, bluish-gray fruit taken from the roundleaf dogwood ( rugosa) growing in the rain garden just outside the Carrier Dome end entrance to ESF’s Gateway Center. Assuming the seed exhibit some form of dormancy, briefly explain the two tests you’d perform before placing the seed into a Baskin and Baskin “Move-Along Experiment.” (10 points)

Just under the heading “Conducting a Move-Along Experiment” on the second page of the assigned article, “When Breaking Seed Dormancy Is a Problem,” by the renowned wife and husband seed scientist team of Carol and Jerry Baskin, the state, “Thus, before initiating this experiment, we determine if the intact seeds or other germination units are permeable and if they are dormant.”

To determine if the seeds are permeable to water (and therefore capable of becoming imbibed – the first phase of the seed germination process), they are weighed both before and after they’ve been incubated on a moist substrate for several days. If the seed do not change in weight – meaning that they have not taken up water – it’s assumed the seed coat is impermeable to water and the seed, therefore, are not a good candidate for this experiment,

On the other hand, if the incubated seed do increase in weight by roughly 20% or more, the seed are assumed to be permeable to water and are then incubated at several temperatures for two to four weeks. If the seed do not germinate, they are assumed to be dormant and therefore, good candidates for further study by means of a “move- along” experiment.

Briefly explain the role that “stratification” and “scarification” play in the germination of seed under controlled conditions. (10 points)

This should be pretty straightforward (though many people do confuse the terms and may not be precisely clear on the role they play in the seed germination process.)

As we’ve learned, if their seed coat is not permeable to water orthodox seed cannot become imbibed, thus preventing germination. To overcome this fairly common hard/impermeable seed coat condition, seed can be “scarified” by one of several means (mechanical, chemical, or heat/hot water) to break through or wear down the seed coat.

“Stratification” is the process of layering or mixing seed with a moist substrate (sand, moss peat, vermiculite, etc.) and then exposing the mixture to a period (typically one to three months) of refrigerated temperatures (33F-50F), referred to as “cool-moist” stratification, warm temperatures (59F-85F), referred to as “warm-moist” stratification, or a sequence of both warm-moist followed by cool-moist conditions.

______out of 20 possible points Identify the material in each of the labeled cups (2 points each), and offer your thoughts on their role in - or as - a desirable propagation medium (3 points each). (Total of 15 points)

(A)__Perlite____ A volcanic rock that is mined, crushed and then heated to create a sterile, light weight, uniform, and readily available at a reasonable cost. It is an extremely porous material that is capable of holding a significant amount of water that is readily available to plant roots. It is an extremely common component of commercial potting/propagation media.

(B)__Sphagnum moss peat___ Sphagnum moss peat is very young, undecomposed moss vegetation harvested from drained bogs, then milled/shredded to various degrees of fineness, depending on the use of the material. Similar to perlite it is sterile, relatively light weight, very uniform, readily available and, most important, capable of holding ten to twenty times its weight in water while simultaneously remaining highly porous. Its primary horticulture-related limitation is that it is “hydrophobic,” meaning that it can be difficult to uniformly re-wet if it gets dry. There are also significant concerns regarding its sustainability as bogs from which it is harvested often never recover.

(C)__Commercial Moss Peat-Based Mix___ This happens to be MetroMix 852, that, according to the label of the current lot is made up of 50-60% composted pine bark, Canadian sphagnum peat moss, perlite, vermiculite and dolomitic limestone. I chose this mix to illustrate how the above materials (perlite and sphagnum most peat) are often combined in manufactured potting/propagation media. As compared to the Redi-Earth propagation mix we’ve used for some of our lab exercises, it tends to be more coarse and more dense. This would make it generally less desirable for seed propagation as “seed to soil contact” might not be good. However, if water management was precise, it could be successfully used for the propagation of many types of woody and shrub cuttings – even though it tends to be used mostly for potting up already rooted cuttings and well-developed seedlings.

Now that you’ve cracked the code for germinating Roundleaf dogwood seed at rates approaching 100% (first question on this exam;-), you’re looking for an inexpensive seed germination media. Before accepting a proposal from the Onondaga County Resource Recovery Agency (OCRRA) for compost made from a combination of food waste (grocery stores, restaurants, food manufactures, schools, etc.) and yard waste (leaves, grass clippings, tree/shrub prunings, etc.), what traits must your germination media meet? (10 points)

Straight from the textbook, “for good results, the following characteristics (for a propagation medium) are required:”

Adequate physical support for propagules Highly decomposed/stable Easy to wet/rewet (not hydrophobic) Sufficiently porous so excess water drains readily Free from pests Low soluble salt/salinity levels Good cation exchange capacity (CEC) Consistent quality Readily available Economical

______out of 25 possible points

What are the names of two of the three journals published by the American Society for Horticultural Science? (5 points)

This should be an easy five points – 2.5 points for each correct journal ......

HortTechnology - Written by experts, for experts, HortTechnology brings you reliable, current, peer-reviewed technical information to help solve problems and deal with current challenges in production, education, and extension.

HortScience – Focus is on horticultural information of interest to a broad array of horticulturists. Its goals are to apprise horticultural scientists and others interested in horticulture of scientific and industry developments and of significant research, education, or extension findings or methods.

Journal of the American Society for Horticultural Science - Publishes papers on the results of original research on horticultural and their products or directly related research areas. Its prime function is to communicate mission-oriented, fundamental research to other researchers.

The reason I ask this type of question is that, as I’ve said previously, one of the most valuable things you can take with you from this course is where to find reliable plant propagation-related information. All three of these journals do just that. As a side note, one year I asked this same question on all three hourly exams – and the final, too. And yet, if I recall correctly, only three or four students got complete credit each time – and most didn’t score any points at all. So, the moral of the story is that it’s a good idea to familiarize yourself with all the references I’ve recommended.

After comparing/contrasting the moistened, screened OCRRA compost with the sphagnum moss peat-based SunGro Redi-Earth Plug and Seedling mix on the table, please offer your explanation of why you would/would not use this locally produced medium to germinate roundleaf dogwood seed. (5 points)

There is no a black and white answer to this question as it might be possible for you to come up with a perfectly good reason for using or not using OCRRA compost as a germination medium. I am looking for you to self-assess the logic you used – based on the assigned readings, video, class discussions, observations at Dickman Farms, etc., in addressing this question and grade yourself accordingly.

Having said that, I would lean toward not using it for the following reasons.

First, despite its relatively uniform appearance, it can vary significantly from batch to batch depending upon the materials entering the compost system (food waste from mall food courts is extremely high in salt that can result in some compost batches having very high salinity levels), the weather conditions to which the end product is exposed (it is stored in the open and can therefore be exposed to very hot, dry weather, cool weather featuring torrential downpours, etc,), the location in the stockpile from which the material comes from, etc.

Also, if you pick up the moistened compost and squeeze it, you’ll likely notice it tends to compact somewhat into a loose ball that retains its shape as compared to the Redi-Earth, which tends to fall apart. It also tends to be heavier than the Redi-Earth. Taken together, this suggests that the compost is denser and has a greater range of particle sizes, which means it does not drain as well as the Redi-Earth and, therefore, may become waterlogged if overwatered.

______out of 10 possible points Sketch the diagram that illustrates the distinct phases of seed germination found in the textbook, name the phases, and briefly explain what occurs during each of the phases. (15 points)

The three phases of the seed germination process are:

Phase I – Imbibition during which water is taken up by (orthodox) seeds having water-permeable seed coats.

Phase II – Lag during which there is little to no additional water uptake by imbibed seed, but much metabolic activity that prepares the seed for germination in the third phase.

Phase III – Root radicle protrusion/emergence is the first visible evidence of germination and a seed is said to have “germinated” at the moment that the radical is visible.

Three seed companies have submitted the following sigmoidal germination curves for seed lots of Money Tree (Retireous earlious) you’re considering growing. Label the axis of the graphs, score them (from 1 to 3 - best to worst) to indicate yoour preference for the seed lots, and briefly explain yoour reasoning. (15 points)

The vertical axis is overall germination percentage of the seed lot and the horizontal axis is time (from sowing).

3 - Least Desirable 2 – Less Desirable 1 – Besst

Lowest overall germination Some seed in this lot germinates A few seed germinates quickly, but a nearly equal amount soon after sowing germinates gradually and trails off, but most seed germinates resulting in a lower germination percentage essentially all at once and than the seed lot at right. at the highest overall percentage.

______out of 30 possible points Briefly explain the two steps involved in overcoming “combinational dormancy.” This type of seed dormancy is not very common, but it is exhibited by seed of the upstate New York native, spring- flower Redbud tree (Cercis canadensis). (10 points)

We’ll learn during the fourth lab exercise of the semester that when shed from the tree, redbud seeds have a hard seed coat that is not permeable to water. To overcome this exogenous (physical) dormancy, the seed must be scarified (physically abraded, treated with sulfuric acid, bathed in hot water, etc.) so that the seed coat becomes permeable to water and begins to imbibe.

Once the seed can imbibe, it must then be exposed to a period of cool, moist stratification (essentially replicating overwintering-like conditions) to overcome endogenous (physiological) dormancy resulting from inadequate embryo growth potential.

This combination of dormancy mechanisms gives rise to the concept of “combinational dormancy.”

While you were researching topics for your independent project, I’m sure you spent some time in the library checking out the four reference books I placed on reserve. For full credit on this question you should be in the realistic ballpark of the actual name of two of the four references. (5 points) (Note: These should be more easy points as I brought these references into class one day and implored you to check them out).

Ripped straight from the syllabus – and from encouraging you to check them out as per my comment in parentheses in the question ......

"Plant Propagation: Concepts and Laboratory Exercises"

"Making More Plants: The Science, Art, and Joy of Propagation"

"American Horticultural Society Plant Propagation: The Fully Illustrated Plant-by-Plant Manual of Practical Techniques"

"The Reference Manual of Woody Plant Propagation, From Seed to Tissue Culture"

So, for the last time (or, probably not the last time), do make some time to check these out from the reference desk and become familiar with them. I really do believe you may find them to be helpful before the end of the course!

______out of 15 possible points Extra Credit (answer one question for up to five extra credit points):

Briefly explain the anatomical difference(s) between the Sansevieria and ZZ Plant propagules used in one of our leaf cutting lab studies. (5 points)

Sanseveria is propagated from true leaves that emerge from rhizomes, which are horizontal-growing underground stems.

ZZ plant propagules, meanwhile, are made from leaflets that have been removed from one to two foot long, pinnately compound leaves that also grow from an underground, rhizome-like structure.

Considering that individual ZZ plant leaflets can often be divided into quarters, it’s possible to ultimately obtain several dozen new plants from a single, large leaf. Sanseveria leaves can also be cut into sections, but ultimately yield, at most, a ten to a dozen or so new plants.

Briefly describe what I would see if I were to pull up and look closely at your team’s hardwood stem cuttings later this morning. (This should include all observations – not just the presence or absence of roots.)

The intent of this question was to get a sense of how will you’re staying up with observing your lab exercises. If you chose to answer this question, I’ll definitely be taking a close look at your cuttings to compare what you’re seeing with what I’m seeing. And, even if you didn’t choose to answer this question, I’ll also be checking on your cuttings;-)

(Interestingly, a quick glance suggests only about half of the class decided to answer this question – which suggests to me that at least a few people aren’t making as frequent observations as they could/should?)