Tag Archives: Date palm

Plant parts doing unexpected things: Part 1 (or, Giving transpiration a little boost…)

Image: Wikimedia Commons.

Image: Wikimedia Commons.

All botanists (plant biologists/plant scientists/phytologists…) worthy of the name should be able to state the important roles played by various plant parts. Stems, for example, support the leaves(!), help to conduct water, photosynthates and other solutes to other plant parts, engage in some photosynthesis (primarily when young), and store such materials as starch. Well, so much for the commonplace quartet of functions. As botanists of an enquiring and sufficiently sceptical nature we probably also know that such a list is never complete, and plants can usually be found that defy convention and engage in practices additional to the received wisdom of general texts. So, welcome news that Or Sperling et al. have discovered the phenomenon of ‘transpirational-boosting’* in the date palm. Famously, the date palm (Phoenix dactylifera) grows in desert-like areas of northern Africa and the Middle East. Deserts are defined primarily in terms of low rainfall; consequently, water is a limiting resource to plant growth in that challenging environment. Yet palms are substantial arborescent monocots that can grow to 30 m tall and whose ecological dominance is sustained with uniquely high rates of transpiration. How is this possible in such water-limited regions? Recognising that the high transpiration rates cannot be sustained by soil water supply alone, Sperling et al. examined the reservoir of water within the palm’s stem. Using a combination of heat dissipation, gravimetric sampling and time domain reflectometry (you’ll need to read the open-access paper for the details of these techniques!), they determined that date palms substantially rely on the exploitation and recharge of the stem reservoir in their water budget; stem-located water contributes approximately 25 % of the daily transpiration rate. The date palm stem holds around 1 m3 of water and transpirational losses are recharged by more than 50 litres each night, which, the team argue, is sufficient to maintain daily reuse throughout the growing season. Although irrigated palms were specifically investigated, that still leaves 75 % of the water usage to be supplied externally. Whilst this column is not the place to engage in debate on contentious topics, such as globally growing demands (yes, unintentional pun noted…) on, and concerns over, future availability of fresh water, and not overlooking the issue of salinisation of soil that may accompany such anthropogenic irrigation practices, it is worth just raising the question of how long one can continue to engage in, or justify, human appropriation of water in this way. However, given the socio-economic importance, etc., of date palms – whose genome has been sequenced by Ibrahim S. Al-Mssallem et al. – perhaps there is a suitable case for ‘engineering’ of this magnificent monocot to enhance the contribution of transpirational-boosting**? Or, if we turn this discovery around, what about the rest of the approximately 351,999 other angiosperm species that haven’t been so examined? Might not more of them have evolved this T-B*** mechanism? And, if so, are estimates of future water demand by crops and other plants in need of revision? Botany, not afraid to tackle the big issues of the day (and tomorrow…)! Regardless, date palm is maybe another plant to add to the more conventional ones of cacti and euphorbs as examples of ‘stem succulents’.

* The ever-helpful Mr P Cuttings has kindly given this newly discovered phenomenon its suitably catchy name for the benefit of all plant science textbook writers (etc.) – Ed.

** No inverted commas this time – that must mean that this newly coined term is gaining acceptance by the community at large… – Ed.

*** And, having now been reduced to an initialism (as distinct from the frequently mis-applied term acronym), this phrase seems to be here to stay(?) – Ed.

PDL stops the rot

PDL stops the rot

PDL stops the rot

This item is not about ‘who’d’ve thought it?’, but is firmly in the ‘why would anybody think to try it out in the first place (but aren’t you glad they did!)?’ category.

Husnu Gerengi (Duzce University, Turkey) demonstrates that juice from the fruit of the date palm (Phoenix dactylifera – PDL) inhibits corrosion of aluminium alloy AA7075 in 3.5 % NaCl (the salt strength of ‘average’ seawater). The relevance of this is that the alloy is commonly used in body panels of the cooling system in cars, in hydrogen gas vessels with high-temperature applications, and in the aerospace industry (where you definitely don’t want metal bits corroding and dropping off of the aircraft – not when it’s up in the air anyway).

Although inorganic, anti-corrosion chemicals are used for aluminium alloys, they frequently contain chromates, which are highly toxic, as graphically demonstrated in the film Erin Brockovich. Safer, more environmentally benign solutions are therefore sought. Although date juice seems an unlikely thing to try, experimentation was inspired by anti-corrosion success of Hymn Rehan with leaf extract of PDL. Quite why Rehan was inspired to try out leaf extracts in this way is a mystery for another day (scrutiny of his paper doesn’t reveal the answer). Although date juice contains several sugars, Gerengi suggests that it is the glucose component that is adsorbed onto the aluminium’s surface and is the main component in the inhibitory effect.

[For more on this fascinating area of ‘green chemistry’ and corrosion-inhibition by plant extracts, why not try this review by Ambrish Singh et al. or this one by Joseph Buchweishaija? – Ed.]

Date sex – XY marks the spot

Image: Wikimedia Commons.

Image: Wikimedia Commons.

Dates, the sticky, sweet fruits of the date palm (Phoenix dactylifera), are the product of sexual reproduction in that plant and borne on the female plants of this dioecious species. Globally, about 15 million metric tonnes of dates are produced annually from 100 million date palm trees and represent a staple food in many Middle Eastern and North African nations. Given this economic importance it is important to know if an individual tree is male or female. Up to now breeders have had to wait for 5 years before they could tell the sex of a tree. That process is likely to be speeded up dramatically with the discovery by Eman Al-Dous et al. (Nature Biotechnology; doi:10.1038/nbt.1860) of sequences of the genome that are linked to gender. The work, which represents the first genome sequence of a member of the palm family (Arecaceae) – and, indeed, of the higher taxonomic ranking, the order Arecales – has also identified genetic markers likely to facilitate breeding of traits such as superior fruit quality and more convenient ripening times into the best current cultivars. The group also propose that the date palm employs an XY system of gender inheritance, similar to that used by humans. In case you were wondering, parthenocarpy is known in this species, but the seedless fruit is smaller and of lower quality than the sexually produced product (http://en.wikipedia.org/wiki/Date_%28fruit%29#Food_uses).

Flower unisexuality in dioecious date palm

Date palm flowers

Dioecy has evolved independently several times during the evolution of flowering plants, but knowledge of the mechanisms involved is poor. Phoenix dactylifera is a dioecious species displaying strong dimorphism between pistillate and staminate flowers, and Daher et al. (pp. 255–266) describe the transition of reproductive buds from a bisexual to a unisexual stage. They find that unisexuality of date palm flowers results from cell cycle arrest of sterile sex organs, rather than from cell death.