I have recently arrived in Manila for the First International Symposium on Moringa. And the first thing I have noticed is that Filipinos love moringa in a touchingly genuine way... amor del pueblo as we would say in Spanish, the love of the people. There are no moringas to be seen in the fancy parts of town, but as soon as you are out of them, the moringas spring into view, whether poking up from behind freeway fences, on roadsides, in well tended or abandoned yards, and even allowed to grow on the Baluarte de San Francisco at the colonial Santiago Fort, no doubt allowed to grow there by a gardener who commutes into the touristy Intramuros area from some outlying area, bringing his sincere love of moringa with him and touching all the other moringaphiles who can't help noticing the slightly unkempt crowns of the moringas gamely poking their heads up all over town.
I will translate snippets of UNAM colleague Alicia Castillo's recent (10 November) open letter in Mexican newspaper La Jornada (which you can read here in Spanish): 

"Rosario Robles, the head of SEDATU [the Mexican ministry of "Agrarian, Territorial, and Urban Development," essentially the planning agency and thus with an essential role in disaster response], visited Chamela [19 kms north of the eye, the humble community was almost completely destroyed; it's also right on the highway and so gets more attention than, say, Arroyo Seco, the coastal town that bore the brunt of the eye] and, when she saw that various families had received food and roofing materials [probably the fragile and toxic asbestos roofing material that blew off in the first], she is reported to have told the residents that they should be happy with the aid that they had received. The residents informed her that the "aid" came mostly from private foundations, not the government. Miss Robles was then informed by one of her assistants that the "aid" was still in Guadalajara."

By all lights, it is still in Guadalajara. Castillo goes on to say that

"We insist and demand that the funds (nearly 10 million dollars) mentioned by the subsecretary of the Mexican Secretariat of the Interior, Fernando Aportela, not remain in the Federal District or in Guadalajara but instead be distributed to the needy communities based on a serious evaluation of the damages and immediately to the families who have lost everything, or whose houses have suffered major damage, as well as to those who have lost their means of economic support."

A petition you will be able to sign to this effect is in progress. In the meantime, please share this video in Spanish with English subtitles to everyone you can think of to help combat the idea that the hurricane came and went without damaging any communities: 
I am back from a week out at the collection. I arrived out at the Collection on the coast of Jalisco three days after Hurricane Patricia scored a nearly direct hit on the community where the germplasm collection is located. The botanic garden looks like hell, but most of the plants are already resprouting and there should be no real lasting damage. 
Patricia made landfall in an area of scattered villages around the Chamela-Cuixmala Biosphere Reserve on the coast of Jalisco, Mexico.
Exactly with things like large hurricanes in mind, I make sure to have at least one individual of all of the samples in the germplasm collection duplicated in pots in the shadehouse. That way, if anything happens to one of them, I can propagate the other. We moved the potted plants into my house, which is very sturdy, and they weathered the hurricane fine. The plants in the botanic garden took a very good thrashing (see photos below), but as I say, they should mostly sprout back, so no major damage. The surrounding community of people is another matter. 
Moringa Collection pre-Hurricane Patricia, October 2015
Moringa Collection post-Hurricane Patricia, October 2015
The local communities are simple farming and fishing villages, and it was clear on arriving that the area had taken a major beating. Not wanting to remain at the level of a subjective impression, I wanted concrete data. I organized a house-to-house census in the little town of 100 people in which the Collection is located. So, 27-29 October, I and a bunch of local townspeople visited 274 houses, almost all the buildings in town, to quantify the damage. I had the fortune to have the help of a local high school student, Rubí Ramírez, who in turn mobilized Yirla Cisneros, Belén Cárdenas, Belén Gutiérrez, Ángela Gabriel, and Sandra Macías to help in gathering data. Maricela Godoy also not only helped gather data but also contributed photocopies and other supplies. 
Here are the data we collected: 

1. Roofing type (concrete, asbestos panels, etc.)
2. Percent of the original roofed area now absent
3. Damage to stoves
4. Damage to refrigerators
5. Damage to other appliances
6. Damage to water tanks
7. Damage to electrical meters
8. Damage to walles
9. Other house damages (e.g. doors, furniture)
10. Number of inhabitants, women, men, children

We visited 274 houses home to 950 people, of which 35% are women, 37% are men, and 28% are children. 

A whopping 84% of all houses experienced some loss of roof. 41% lost 75% or more, and 18% lost their entire roof. The most damaged roofs were those made with asbestos panel, galvanized steel, or concrete or clay shingles. The only roofs that consistently escaped damage were those made entirely of reinforced concrete, but only 14% of the roofs in town are concrete. 

The climate here is harsh-- hot and humid. Five days after Patricia came two days of torrential rains that poured through open roofs and soaked mattresses, refrigerators, stoves, and even family photos. In this climate, a thoroughly soaked mattress will never dry out in time before it gets fungus ridden and forever stinky. 
The success of a scientific project like mine, or of a field station like the Chamela station, or the biosphere reserve like Chamela-Cuixmala, depends largely on the goodwill of the neighbors. Scientists in the area have had the benefit of nearly 45 years of good neighbors in the area. Our neighbors need us now and we cannot possibly in good conscience to abandon them. A week after Patricia, they are still there, with the rain falling on their hard-won possessions, the chikungunya- and dengue- carrying mosquitos coming in through the holes in the roof, with no solution in sight. A helping hand would seem in order. 
I am still in Mexico City. My flight, which I had emergency booked to prepare the Collection on Friday afternoon, got canceled. Around noon the collection caretaker moved the potted plants from the shadehouse into the house to protect them from flying around. Pots flying around means plants divorced from their labels, making them scientifically worthless. At 4 o'clock in the afternoon on Friday the collection caretaker said that it was raining pleasantly. At 5 he said that the wind had picked up and that he didn't think that the big drouhardii with the hydraulic experiment would survive. Cell phone service cut out at about 5:45 pm. Shortly thereafter, Patricia made landfall about 10 kms from the Collection. 

At 10:30 pm I tried as many phone numbers as I could in the community, and none in the upper part of town where the Collection is were working. But one in the lower part was. The news was not good. Our friends reported that Patricia had blown the roof off of their house and ruined all of their possessions. 

After that, we haven't been able to get through to anyone in the area. Friends in the area who rode the storm out elsewhere have gone back to their houses and from their lack of communication we infer that they reached home. If they had turned back they would still be within reception. 

The reports of "less damage than expected" probably just reflect the fact that the hurricane did not hit a large city, and the general bias of society against poor people. From the fragmentary reports I've been getting, far as I can tell, the damage to the humble communities near the Collection in the path of the hurricane was severe. Building materials are expensive, and it is hard to imagine how someone who makes his living growing bananas on a small scale-- never a very lucrative trade-- will be able to make a thousand dollars in repairs, especially when his entire crop of bananas are flattened to the ground. 

Back in 2011, Hurricane Jova snapped the largest tree in the Collection, a big "iguanero" (Caesalpinia eriostachys), right in half. It has since resprouted. Moringas are tough. The rarest moringas in the botanic garden are mostly species with big tubers, so even if the aerial stems are damaged I suspect that they'll come back. The saplings of the tree species were probably heavily damaged. Fortunately, these will either resprout or, in most cases, I have duplicates in the shadehouse that I can replace them with. The M. hildebrandtii that I collected in Madagascar, and the M. concanensis that I collected in Tamil Nadu, though, are unique and I haven't propagated them yet. So those will be priorities. I suspect that the concanensis will resprout even if badly damaged, and I hope the hildebrandtii would too. Whatever the case, it's clear I need to get out there soon, but I think the Collection should come through despite the setback.

More worrisome is how the neighbors are doing, a lot of whom live in rickety houses. The one neighbor who reported losing his roof lived in a concrete house, albeit with corrugated asbestos roofing prone to flying away. A fair number of neighbors live in more precarious houses and with precarious livelihoods like agriculture and fishing. I suspect that the "less damage than expected" is sounding pretty hollow to them right now. Let's not forget about them. 


Recovery of the Collection and fortifying it against future storms will depend to a large degree this year on the renewal of my grant RT200515 of the Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica of the Universidad Nacional Autónoma de México... fingers crossed.
If you take a sample from the trunk of a Moringa tree, you will see that the wood cells have starch, even the cells way in the center of the stem. Starch is the way that plants store the products of photosynthesis, so it’s a crucial energy reserve. Its presence in cells is usually taken as evidence that the cells are alive. For one thing, it would be wasteful to make the starch and then let the cells die without using it. For another, bacteria often degrade starch fairly quickly when a piece of wood dies, so it would be surprising to find starch persisting for very long. But these are just conjectures that need testing.

Just how much of the trunk of a moringa consists of living cells is an important key to understanding how they can resist drought so well. Looking at the swollen trunk of one of the fat bottle tree moringas, like M. drouhardii or M. stenopetala, it’s easy to think that all that water storing trunk tissue is drawn upon to keep the plant going through drought. But the only way really to tell is by seeing whether the cells are alive and functioning or not.

This is exactly what UNAM master’s student Matiss Castorena’s project involves. He is carrying out a comparative study to see how the amount of living tissue in trunks varies across species. To complement this study, he is looking in detail at how living tissue is distributed within a single large M. stenopetala tree. He has taken cores all around and the length of two trunks of the tree. He then takes these cores and incubates them in a solution of triphenyl tetrazolium chloride (TTC). The enzymes involved in metabolism reduce TTC to triphenyl formazan (TPF). The neat thing about this is that TTC is soluble but TPF is not only insoluble but is a deep red color. This means that very active living cells become markedly red, sluggishly metabolically active cells various shades of pink, and dead cells don’t change color at all. This means that along a core sample from the outside to the inside of the trunk, Matiss can map the distribution of metabolically active cells. This is important because only the living areas are involved in conducting water, and in storing and mobilizing photosynthetic products, both factors that are very important in plant functional aspects like supporting the leaves and resisting drought.

What Matiss is finding is very interesting. It turns out that very little of the trunk is alive. Moringas seem to be just a thin layer of live wood overlain on a central core of dead or very metabolically sluggish cells. So those fat trunks, that would seem to be giant water tanks, might not be serving in storage as much as we think. Soon Matiss will be sampling our large Moringa drouhardii from our sap flow experiment, and this will help us to understand the data that those sensors gather.  Keep up the good work Matiss!
Matiss in the field with Cipatli
Outer wood (top L) stains red, dead inner wood not at all
AND he can cook! Here with the Latvian delicacy pankukas :)


Ongoing fieldwork, collection maintenance, experiments, and laboratory work are being made possible by grant RT200515 of the Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica of the Universidad Nacional Autónoma de México
The vessels that move water in plants increase predictably in a similar way across species. This means that size, regardless of species, predicts the size of the vessels. A 50 meter tree will have vessels at the base of its trunk of similar diameter, whether it’s a Eucalyptus in Australia or an elm in Mexico. The going explanation for this universal pattern is that natural selection acts on similar ways across species in such a way that trees maintain hydraulic resistance constant as they increase in size. See this previous post for more details and references on this tip-to-base vessel widening.

If this pattern really is the product of natural selection, then several implicit predictions immediately emerge, and these predictions have never been tested. First, natural selection acts on variation within populations, so we would expect that variation in the vessel diameter-stem length relationship should be observable. What is more, this variation should impact performance. Plants with vessels that are “too wide” for their trunk height should be vulnerable to embolism in their vessels. Plants with vessels that are “too narrow” for their height should suffer because of low conduction and low productivity. Goldilocks style, there should be a sweet spot in the middle where vulnerability and productivity just balance out, and this is where the majority of plants should lie. Finally, to be the target of natural selection, this variation with peformance consequences must be heritable.

Because most wood plants grow so slowly, these aspects, especially heritability, are hard to test. Thanks to moringa’s spectacular growth rate, UNAM PhD student Alberto Echeverría can use the tree to test all of these predictions. He planted a very genetically diverse selection of moringa seeds a month ago, and the biggest trees are already chest high. In a couple of months, once they get to about 3 meters, Alberto will be able to start harvesting them and trying to detect that variation in vessel-plant size proportionality that is the entire basis of his project. Good luck Alberto!
Alberto's trees are already chest high
iguana among the moringas


Ongoing fieldwork, collection maintenance, experiments, and laboratory work are being made possible by grant RT200515 of the Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica of the Universidad Nacional Autónoma de México
All moringaphiles know that there is no way to kill a moringa with drought. But how do they do it? For that matter, why do plants in general suffer from drought? Plant biologists are still trying to figure out exactly what mechanisms cause plants to die or suffer from lack of water. Everyone agrees that it has something to do with water, especially the way that plants move water. Plants do this through little tubes called vessels (see a previous post on vessels). Big wide vessels conduct a lot of water because there is relatively little friction per unit water volume with the vessels walls. However, it also seems that it is easier to break the conductive stream in wide vessels, making them vulnerable to embolisms that rob the leaves of needed water. Narrow vessels make it harder to move water because of the greater water-wall friction, but narrow vessels seem to resist embolisms better. Because of these differing resistances to embolism, narrow versus wide vessels are regarded as adaptations to differing environments. Plants in dry areas like deserts, where drought and therefore embolism are ever-present risks, should have narrow, embolism-resistant vessels. Plants in wet areas, where embolism risk is lower, can afford to have wide vessels.

Recent data shows that this traditional picture is more complicated. Vessels all start out at more or less the same diameters in the leaves, and then widen gradually down the stem. This widening maintains hydraulic resistance constant as the tree grows and the conductive path lengthens. This means that a small plant in a rainforest will have similar sized vessels as a similar-sized desert plant. Plants in the desert on average are smaller than those in the rainforest. Given the dependence of vessel diameter on plant size, this is why vessels in desert plants are on average narrower than in rainforest plants. What this means is that we need to take plant size into account in understanding how vulnerable a given plant is to embolism.

This is what UNAM postdoc Diana Soriano is going to test. Using a low genetic diversity line of Moringa olefiera bred here at the Collection, Diana is planting seeds once a month to generate a population of individuals of different sizes to see how plant size affect vulnerability to embolism. The fast growth of moringa makes the experiment possible. Whereas the growth of most woody plants is measured on a scale of years, moringa trees will grow to over 3 meters tall in a matter of months. Diana has already planted three crops of seeds, and is getting her scientific gear ready to take out to the Collection to start measurements. 
Diana and Alberto laying out experiment
Diana with 1-month old seedlings. Coming along!
Diana cooking up some leaves for moringa quesadillas


Ongoing fieldwork, collection maintenance, experiments, and laboratory work are being made possible by grant RT200515 of the Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica of the Universidad Nacional Autónoma de México
A member of the northeast African clade of Moringa, M. borziana is a remarkable dwarf species. It has a large underground tuber and one or two stems, which are usually just 1-2 meters tall. The species often flowers leafless, or just as it leafs out, such that the plants are in fruit by the time they are fully leafed out. The flowers are big, yellow, and probably bee pollinated. Only one is flowering at the moment, from the coastal dry tropical woodlands of eastern Kenya. They might not be self-compatible so getting seeds seems unlikely just yet, but this will only be a matter of time as the rest of the plants mature and they synchronize their flowering. 

Rapidly maturing buds on Moringa borziana in the International Moringa Germplasm Collection
Flowers from a different individual-- we'll see how similar the flowers are between individuals once they all start blooming.
One of the great things about the genus Moringa is that, with such a range of shapes and sizes, it can help answer basic questions about how plants in general evolve. In this case, University of Padua collaborators Tommaso Anfodillo and Vinicio Carraro, and UNAM postdoc Diana Soriano and PhD student Alberto Echeverría and I are using a very tall, skinny Moringa drouhardii individual in the Collection to address basic questions about how plants move water from their roots to their leaves, and how they manage to do this even as they increase in height.

Most flowering plants move water in pipes called vessels. As a tree gets taller, the vessel pathway must also get longer. If nothing else in the system changes, and the only thing that happens is that the vessel pathway gets longer, then the resistance due to friction between the sap and the vessel walls increases. This increase turns out to be linearly related to length, that is, flow rate will drop as a linear (not exponential) function of vessel length increase. This phenomenon can be observed, irritatingly, in my house: the kitchen tap ended up farther away from the water tank than planned, and even though we put in ¾” pipe, the flow is notably lower than in the hose bibb halfway between the kitchen and the tank. For various reasons vessels have to be very narrow at the ends, at the stem tips and in the leaves. So narrow, in fact, that if trees had vessels the lengths of their trunks that were the same diameter as the apical vessels, then they would conduct less and less water they taller they get—a penalty for growing in height.

Fortunately, fluid mechanics has a magical trick up its sleeve: small increases in pipe diameter lead to very large (exponential, to the fourth power to be precise) increases in flow rate. This is why, with the same amount of suction, you get a quick mouthful of your drink through a wide straw and just a little through a narrow one. As it turns out, what happens in trees is that vessels widen from the stem tip to the base. This maintains the hydraulic resistance constant even as trees grow in height and the conductive path becomes longer and resistance, minus widening, would increase. Lots of people have worked on this, but work in my lab and by collaborators is listed at the end.

This tip-to-base widening has potentially important implications for how sap flow in trees generally is studied. This is because the volume of fluid moving past any given point in a pipe remains constant. If the pipe changes in diameter, as we know tree vessels do, then the fluid must speed up as the vessels narrow. So, even along a single tree trunk, the actual speed of sap flow should depend on how far the measurement is taken from the stem tip, because of tip-to-base vessel widening. The amount of sap moved along the length of a trunk should remain constant, but it should be slow at the base and fast at the tip.

This prediction has been hard to test in much detail because in most normal trees, as they get taller they become intricately branched. So as we move down the stem, the tip-to-base widening pattern is complicated by incoming vessels from side branches. This is where Moringa comes in. 
The upper 7 meters or so of the Moringa drouhardii in question (at left)
Most Moringa species tend to grow single unbranched trunks as saplings, and some continue this habit well into early adulthood. Probably the most extreme in this respect are the Malagasy giants M. drouhardii and M. hildebrandtii. Of the dozens of individuals in the Collection, we selected a particularly tall M. drouhardii, which, despite being 9 meters tall or so (about 30 feet), has just two main trunks, which branch off about 2 mi above the ground. Each then soars upward to terminate in a single rosette of large leaves.

This is the perfect situation—a single branch that is 7 meters tall with a single growing point. The vessels are narrow at the tips of these branches and wide at the bases. Vinicio home-made special sensors, and Tommaso hand-carried them to us. Then Alberto and Diana soldered the whole system together and connected the sensors to a datalogger. They installed the sensors in the tree and lovingly built little roofs to protect the sensors from the brutal tropical rain and insulated the trunk to protect the sensors from the brutal tropical sun.

The experiment has just started, but the flow does seem to be slower in the lower sensors. This means that an experiment with Moringa should help provide helpful guidelines for factoring stem length into measurements of sap flow for plants in general. In turn, it will also help unlock the secrets of Moringa’s extraordinary drought resistance. 

UNAM PhD student Alberto Echeverría and postdoc Diana Soriano tending the sensors they have carefully installed in this long, tall Moringa drouhardii. The cables connect the sensors to the datalogger.
Alberto and Diana getting the sensors ready
Diana and Alberto connecting the sensors to the datalogger to test them before installing them in the tree.
The sensors are connected to the datalogger, which we put inside the trusty Volkswagen van...
...which has a solar panel that charges a deep cycle battery


This project is made possible by grant RT200515 of the Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica of the Universidad Nacional Autónoma de México


Anfodillo T, V Carraro, M Carrer, C Fior, S Rossi 2006 Convergent tapering of xylem conduits in different woody species. New Phytol 169: 279–290.

Anfodillo, T., G. Petit, and A. Crivellaro. (2013). Axial conduit widening in woody species: a still neglected anatomical pattern. IAWA Journal 34(4): 352-364.

Bettiati D, G Petit, T Anfodillo 2012 Testing the equi-resistance principle of the xylem transport system in a small ash tree: empirical support from anatomical analyses. Tree Phys doi:10.1093/treephys/tpr137

Olson, M. E., T. Anfodillo, J. A. Rosell, G. Petit, A. Crivellaro, S. Isnard, C. León-Gómez, L. O. Alvarado-Cárdenas, and M. Castorena. 2014. Universal hydraulics of the flowering plants: vessel diameter scales with stem length across angiosperm lineages, habits and climates. Ecology Letters 17: 988-997.

Olson, M. E., J. A. Rosell, C. León, S. Zamora, A. Weeks, L. O. Alvarado-Cárdenas, N. I. Cacho, and J. Grant. 2013. Convergent vessel diameter-stem diameter scaling across five clades of New- and Old- World eudicots from desert to rain forest. International Journal of Plant Sciences 174(7):1062–1078.

Olson, M. E. and J. A. Rosell. 2013. Vessel diameter–stem diameter scaling across woody angiosperms and the ecological causes of xylem vessel diameter variation. New Phytologist 197: 1204–1213.

Petit G, T Anfodillo 2009 Plant physiology in theory and practice: an analysis of the WBE model for vasuclar plants. Journal of Theoretical Biology 259: 1-4.

Rosell, J. A, and M. E. Olson. 2014. Do lianas really have wide vessels? Vessel diameter-stem length scaling in non self-supporting plants. Perspectives in Plant Ecology, Evolution, and Systematics 16: 288-295.