Quantifying Developmental Stages

Guretzky et al. Author

05/10/2019 Added

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This video covers how to characterize developmental stages of tillers and quantify them.

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[00:00:06.240]Hello and welcome to the Quantifying Developmental Stages lesson.
[00:00:11.280]I'm Amy Kohmetscher with the University of Nebraska Lincoln,
[00:00:15.042]and I will be taking you through this lesson.
[00:00:18.400]This lesson was created by John Guertsky and Christopher Barber.
[00:00:23.120]The development of this lesson was made possible by a grant from the USDA NIFA
[00:00:29.348]Agriculture and Food Research Initiative Competitive Grants Program on sustainable
[00:00:35.891]Bioenergy.
[00:00:37.880]Classification of tillers into developmental stages and calculation of
[00:00:43.373]tiller numbers and tiller weights by development stage is a useful means of
[00:00:49.254]characterizing tiller populations in applying management strategies to
[00:00:54.747]perennial grass based production systems.
[00:00:59.200]Grasses may be classified into vegetative, elongation,
[00:01:04.432]reproductive and seed production stages of development.
[00:01:11.080]During vegetative stages, the stem has not elongated,
[00:01:15.662]the growing point remains at or below the soil surface,
[00:01:20.414]and generally one to six collared leaves occur on each tiller.
[00:01:28.320]In this picture, the first leaf has emerged through the
[00:01:32.626]coleoptyl, but it has yet to develop a collar.
[00:01:37.200]Therefore, it is classified as V0.
[00:01:42.560]This picture illustrates a tiller at V1 stage where the first leaf is collared
[00:01:51.588]after two collared leaves have appeared.
[00:01:56.680]The tiller is in the V2 stage.
[00:02:04.080]The V3 stage has three collared leaves.
[00:02:10.240]This seedling has five leaves, but only four of them have collars.
[00:02:16.000]Therefore the seedling is in the V4 stage.
[00:02:23.360]If a plant has the first leaf collared and has turned brown,
[00:02:28.208]a second leaf that is collared and is still green,
[00:02:32.261]1/3 leaf with a collar that's green, and a fourth leaf with no collar that is
[00:02:38.460]green, what is the stage of this plant?
[00:02:44.720]If you said V3, you are correct.
[00:02:50.760]An elongating tiller has palpable nodes and elongating inner nodes.
[00:02:57.560]Most leaves have collared and are maturing quickly.
[00:03:03.320]After three to five nodes are palpable, the plant is preparing for reproduction.
[00:03:10.080]In staging of elongating tillers, you count the number of palpable nodes.
[00:03:16.360]Palpable nodes are those nodes that you can feel as you run your fingers down the
[00:03:21.902]stem.
[00:03:23.440]Although the sheath of each leaf is attached at a node,
[00:03:27.018]the extent to which you will be able to see or feel the nodes depends on how much
[00:03:32.258]the inner nodes have elongated.
[00:03:35.720]If a plant has three leaves, the first of which which is collared and
[00:03:41.320]brown, the second is collared and green, and the third is collared and green and
[00:03:47.800]three palpable nodes along the stem, what is the stage of the tiller?
[00:03:57.440]If you said E3, you are correct.
[00:04:03.440]Reproductive tillers are characterized by a fully elongated stem.
[00:04:08.840]Generally, 3 to 6 nodes are present and a whirl is
[00:04:13.136]produced at the top of the stem containing the inflorescence.
[00:04:18.960]When the inflorescence is fully exposed, fertilization will occur.
[00:04:24.720]After fertilization, tillers enter the seed production and
[00:04:29.248]ripening phase.
[00:04:32.000]When quantifying developmental stages of tillers,
[00:04:36.200]it is important to note that reproductive tillers may be classified into 6R stages
[00:04:43.174]that vary based on emergence and visibility of the inflorescence and
[00:04:48.971]timing of anthesis and fertilization.
[00:04:52.960]After fertilization, tillers enter the seed production and
[00:04:57.265]ripening phase.
[00:05:00.120]The seed production and ripening phase can be divided into 6 stages that
[00:05:05.328]describe development and maturity of the karyopsis or grain.
[00:05:10.880]The seed production and ripening stages begin at S0,
[00:05:15.229]the stage when the karyopsis becomes visible, and cease in S5,
[00:05:20.400]the stage when the endosperm is dry and the seed is ripe.
[00:05:26.560]Quantitative indices have been developed to characterize tiller populations.
[00:05:35.200]2 Indices that have been applied successfully to perennial grasses include
[00:05:43.297]mean stage count MSC and mean stage weight MSW.
[00:05:50.160]The mean stage count calculation accounts for the number of tillers within each
[00:05:56.578]developmental stage relative to the total number of tillers that occur within a
[00:06:02.997]population.
[00:06:05.040]The mean stage weight calculation accounts for the total dry weight of
[00:06:10.470]tillers within each developmental stage relative to the total weight of tillers
[00:06:16.589]that occur within a population.
[00:06:22.880]The formula for mean stage count looks like this.
[00:06:28.520]MSC equals the summation of S times n / C. The formula itself is fairly simple,
[00:06:39.055]but we still need to know what the variables are.
[00:06:46.760]S is the stage index, which I will show you how to calculate in
[00:06:51.213]a minute.
[00:06:54.000]Little N equals the number of shoots in stage S.
[00:06:58.958]C equals the total number of shoots in the sample.
[00:07:06.320]Take a second to jot this down, and then we'll move on to show you how to
[00:07:11.233]calculate the stage index.
[00:07:15.600]This table shows us the vegetative, elongative, and reproductive stages,
[00:07:21.651]their numerical indices, and a description for perennial grasses
[00:07:27.039]at that stage.
[00:07:29.160]The table here is an abbreviated version of the one published in the reference
[00:07:34.501]listed at the bottom of the table.
[00:07:37.800]For simplification purposes, germination and seed production stages
[00:07:42.840]are not included within our table.
[00:07:48.040]On the left hand side are the developmental stages and in the center is
[00:07:52.880]the numerical indices.
[00:07:55.320]This is how we're going to calculate S in the mean stage count formula.
[00:08:00.840]If you take a look at the vegetative stages,
[00:08:04.142]you'll see that there are some formulas that have a number divided by N plus 0.9.
[00:08:10.800]This is the formula we're going to use to calculate S.
[00:08:15.083]Notice the formula changes slightly when you get into the elongation stage of
[00:08:21.158]plant development.
[00:08:25.520]Then at the reproductive stage, S becomes a constant number again.
[00:08:32.280]Now that you see how to calculate S, we will move on to do a practice problem.
[00:08:40.720]Here is the table we're going to use to help us calculate the mean stage count.
[00:08:46.560]First, let's take a look at the notes at the
[00:08:49.398]bottom.
[00:08:50.920]The grass produces 6 leaves before elongation,
[00:08:55.200]which also means the grass elevates 6 nodes before reproduction.
[00:09:02.520]So we can substitute 6 in for all the capital Ns.
[00:09:09.640]Now that we've done that, we can use the number of tillers which
[00:09:16.252]has been given to us and calculate S times little n.
[00:09:21.643]Now that we've calculated S times will end.
[00:09:26.360]We need to find the summation of those numbers, so we'll add them together.
[00:09:34.320]Now that we've calculated for S * n and for C,
[00:09:38.231]we can go back and plug those into the mean stage count formula.
[00:09:44.280]Remember, mean stage count equals the summation of
[00:09:50.513]S times little n / C.
[00:09:53.840]For our sample problem, the summation of S times little n = 32.
[00:10:07.299]6 and C = 1732.6 / 17 equals MSC.
[00:10:17.120]MSC equals about 1.9.
[00:10:20.840]Once you round, take a minute to pause the video and try
[00:10:27.304]the problem out on your own.
[00:10:31.480]Once you've finished the calculation and have verified we have the correct answer,
[00:10:36.655]go ahead and press play again to finish this lesson.
[00:10:42.600]Now that we've calculated the mean stage count to be 1.9,
[00:10:46.875]let's take a minute to think about what that means to us in terms of application.
[00:10:55.320]The following table illustrates with the mean stage count value for the population
[00:11:01.147]of tillers.
[00:11:01.920]You calculated means in terms of management for a mean stage count of 1 to
[00:11:11.109]1.9.
[00:11:12.000]The majority of tillers are in a vegetative stage.
[00:11:15.720]If you operate a grazing operation, this is the ideal developmental stage for
[00:11:21.774]harvest of forage through your livestock as the new leaves and tillers produced
[00:11:27.984]are high in forage quality.
[00:11:32.280]At this stage, the stem apex or growing point remains at
[00:11:36.648]ground level and is not removed with defoliation.
[00:11:41.200]However, reserves of carbohydrate and protein in
[00:11:46.100]stem bases.
[00:11:49.280]However, reserves of carbohydrate and protein in
[00:11:53.356]stem bases and below ground storage organs remain low and may be depleted by
[00:11:59.761]overgrazing.
[00:12:03.920]A mean stage count of 2 to 2. 9 marks a period of vulnerability of
[00:12:09.696]tillers to defoliation.
[00:12:12.520]Mowing or grazing during this time frame will result in removal of the growing
[00:12:18.349]point or the shoot apex.
[00:12:20.760]New tillers must be initiated from axillary buds on the crown of the parent
[00:12:26.434]tiller, rhizomes, or stolens.
[00:12:29.400]Many of these buds are not fully developed and thus growth of new tillers
[00:12:34.218]may be slow.
[00:12:36.840]The ideal time period of harvesting perennial grasses for hay production is
[00:12:42.920]during a mean stage count of 3 to 3.9.
[00:12:47.080]At this time, forage quality and forage yield are
[00:12:51.013]optimized.
[00:12:52.400]Forage quality will continue to decline as mean stage count increases.
[00:13:00.480]Maximal yields for biomass energy production purposes may be attained when
[00:13:06.788]mean stage count of 4 to 4. 9 is reached as biomass yields continue
[00:13:12.507]to increase during seed production stages.
[00:13:18.360]Now that we've discussed what the mean stage count means in terms of application,
[00:13:24.136]let's move on to the mean stage weight calculation.
[00:13:28.920]Mean stage count and mean stage weight calculations are fairly similar,
[00:13:34.261]we just have to exchange a couple of the variables.
[00:13:38.840]Keep in mind mean stage count equals the summation of S times little N all over C,
[00:13:47.070]where S equals the stage index and N equals the number of shoots in stage S,
[00:13:54.706]and C equals the total number of shoots in the sample.
[00:14:02.960]Now we'll just go over here and compare that to the mean stage weight calculation.
[00:14:09.280]Mean stage weight equals the sum of S * D divided by WS still equals the stage
[00:14:17.790]index, and D equals the total dry weight of the
[00:14:22.962]shoots in each stage S.
[00:14:25.440]And W equals total dry weight of the sample.
[00:14:33.000]We'll draw a line here to help us divide these and take a look to compare.
[00:14:38.840]We still have the summation at the top, and in mean stage weight we take the
[00:14:45.167]stage index times the total dry weight of shoots in each stage S instead of the
[00:14:51.741]number of shoots in stage S. And on the bottom,
[00:14:55.686]in the mean stage weight calculation, we use the total dry weight of the sample
[00:15:02.260]instead of the total number of shoots in the sample that we used in the mean stage
[00:15:09.080]count calculation.
[00:15:12.440]Now we've switched from the number of shoots to the weight of the shoots,
[00:15:17.415]but the calculation method stays the same.
[00:15:21.520]All we have to do is exchange some of the variables and use the calculation method
[00:15:27.483]that we've practiced today in this lesson to calculate mean stage weight.
[00:15:35.320]Now, we won't be doing a mean stage weight
[00:15:38.116]calculation example problem in this lesson,
[00:15:40.978]but there are some problems to do in your homework.
[00:15:45.520]So take a minute to write down this formula and make sure to practice the
[00:15:50.408]mean stage weight calculations provided in your homework.
[00:15:57.360]The reference that the tables provided in this video were taken from is listed here
[00:16:02.194]on this slide.
[00:16:04.160]If you would like to see the expanded tables, feel free to visit this reference.
[00:16:11.080]Thank you for taking the time to view the Quantifying Developmental Stages lesson,
[00:16:16.288]and good luck with your homework.

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