I have forwarded your question to my former PhD student.  Personally, I find these anthropomorphic terms distinctly unhelpful. Regards, Hans 

@Hans Lambers Sir: These terms at this stage of research probably gives a feeling -  "This is gonna be something very interesting...what does this really mean...Can I apply it in my research...if yes, how!" hence the inquisition..!

Thank you Sir :-)

I urge you NOT to adopt those terms, as they are distinctly unhelpful.  You can have feelings, but to ascribe feelings to plants is not something I would recommend. :-)

I understand this now Sir! Thank you very much for the guidance... :-)

Thanks to Hendrik Poorter Sir as well (another plant physiologist I look up to)... :-)

I feel honored...Thank you very much!! :-)

Hi, Ankita, Let's say simple: "optimistic growth" is a growth by expansion/differentiation, but "pessimistic" is a growth by development (new organs, for example, with more de-differentiated tissue) with keeping plants more dense. But, of course, pessimistic and optimistic plant growth is not a very good terms. 

If that is what is meant, Taras, it would be better to use those terms, rather than terms that make you wonder and interpret them in numerous ways.  Hans 

@Taras Sir:

This is what I read in the article by Poorter et al. (2012) "........pessimistic species that persist in the shaded understory show lateral crown spread to optimize current light capture, whereas optimistic species obtain brighter light conditions in the forest canopy by rapidly increasing their tree height and crown size with increasing diameter."

I am a little confused. If pessimistic growth leads to denser plants, then they could not be the shaded understory plants as they have sparse and less dense branching architecture. I hope I have not misunderstood the terms as you explained.

I should rather refrain from using the terminologies that are confusing as suggested by Hans Sir..

Thank You..!

Maybe strategies of longevity vs. competition would be more correct terminology, or even better, conservative vs. risky carbon allocation patterns which applies to 2 common and very different strategies of trees:

Some species allocate a great deal of resources to the early development of a large root system, and an adult tree may keep enough carbohydrates stored to keep them alive for a couple of years.  They may also make a greater investment in dense wood, thick bark, and secondary compounds.  This strategy allows them to survive frequent catastrophic events (ie. they are "pessimistic"). 

In contrast, other species allocate a much larger proportion of carbon to above-ground growth.  They grow very quickly to compete with adjacent trees, but make less investment in durable tissues and carbohydrate storage ("optimistic").  Many tree species with this more competitive growth strategy are shorter-lived, and dominate on sites with a low frequency of disturbance.  Of course there are many species that are intermediate between these 2 strategies. 

@Jennifer A. Franklin: Thank you Ma'am, for clarification of the terms :)

Can we say here that the conservative plant strategies indicate the slower growth rate as compared to the risky carbon allocation patterns?

Thank you...!!

Ankita :)

Yes, I would say that the above ground growth rate as measured by height growth, fresh mass, or leaf area is typically slower for species with a conservative strategy.  But you have to be careful how you measure growth.   This might not be the case for dry mass, because a conservative species could have a greater lignin content.  Below ground, biomass accumulation rate may be actually be greater in more conservative species in their first few years of growth, because they allocate a greater proportion of resources to those protected tissues.

Hi, Ankita, Jennifer explain everythingb excellent, fhe case of the tree species in the specific envinronment. and for specific plant species. But if envinronmemnt will changes everyting may changes as well. It may mena that "pessimistic plant species" become "optimistic".. So, this term is just arbitrary definition.. 

@Jennifer Ma'am: This is interesting! Ma'am, do we have examples of tree species  showing such strategies or it is that any species may show both the strategies during its life-time depending on the ambient environmental conditions (as also mentioned by Taras Sir)?

Also, can we ascribe these strategies to other growth forms too, like shrubs?

Thank You!

I am most familiar with trees of North America, and can give you a examples of these.

Quercus rubra has a conservative strategy.  The root can grow to a meter in depth and over 15 mm diameter in the first year, but the shoot is rarely taller than 0.5 m in this time.  It is tolerant of drought and has very large rays in the wood in which to store starch.  In research plots that are burned annually, seedlings were top killed but produced a new shoot each year for  25 years.  Many shrubs such as Elaeagnus umbellata use this strategy also.  When the Quercus reaches a few cm in diameter it produces a very thick bark to protect it from fire, herbivores, and temperature extremes.  A preformed growth pattern, and thick, lignified leaves, ability to survive in the shade, and high levels of tannins are also characteristics of its conservative strategy and it can live to 200 years.

Robinia pseudoacacia is a early successional species that does not have a conservative strategy.  It produces a shallow and spreading root system for rapid nutrient uptake, and the shoot can grow to 1 m tall in the first year.  It will sprout from the root system, but is susceptible to fire and frost damage at all stages of growth and cannot tolerate any shade.  It has a neoformed (continuous) growth pattern.  It has thin leaves without trichomes and few secondary compounds, and both wood and leaves are readily attacked by insects.   It rarely lives to more than 25 years in its native range. 

Liriodendron tulipifera begins life with a competitive strategy, but as it reaches maturity it develops a thick bark and extensive root system, adopting a somewhat more conservative strategy. 

Hi, Ankita, there are some recent articles on the topics. I hope this will be interesting for you,

Huber, H., Brouwer, J., Wettberg, E. J., During, H. J., & Anten, N. P. (2014). More cells, bigger cells or simply reorganization? Alternative mechanisms leading to changed internode architecture under contrasting stress regimes. New Phytologist, 201(1), 193-204.

Watari, R., Nagashima, H., & Hirose, T. (2014). Stem extension and mechanical stability of Xanthium canadense grown in an open or in a dense stand. Annals of botany, mcu088.

@Jennifer Ma'am: Thank you Ma'am !! Can we say that conservative and risky carbon allocation strategies may help in explaining the trade-offs between resource allocation for above-ground and below-ground plant parts?

Ma'am, does not this also explains why shade-grown individuals harbour lesser flowering units in comparison to their sun-grown conterparts, as in, shaded plants being conservative, allocate lesser resources to the above ground plant parts that also includes floral parts.

Thank you Ma'am  :-)

@Taras Sir: Thank you Sir for the references... shall go through them! :-)

For plant behaviour in growth and development processes, you can give a look to the following paper:

ZOU, YunLan; CHAI, Bencheng. The research on Virtual Plants Growth Based on DLA Model. Physics Procedia, 2012, 25: 1887-1891.

A. Hodge. Root decisions. Plant, Cell & Environment, 22:811-820, 2009.

Prusinkiewicz P. Modelling plant growth and development, Current Opinion In Plant Biology 7 (1), pp.79−83, 2004

Trewavas A., Green plants as intelligent organisms. Trends in Plant Science, 10(9):413–419, 2005

YAN, H. P., Kang, M. Z., De Reffye, P., & Dingkuhn, M. (2004). A dynamic, architectural plant model simulating resource‐dependent growth. Annals of botany, 93(5), 591-602.

Of course, a rich literature is available on this topic. However, the key element that drives the optimistic or pessimistic behavior of the plant is always the availability of resources and the principle of maximum efficiency.

 Ulmus pumila is a dominant tree species in semiarid Hunshandake Sandy Land in Northern China. It shows both the strategies during its life-time, I have studied that, please find my paper if you are interesting for it.

Su H, Li Y, Liu W, Xu H, Sun O. Changes in water use with growth in Ulmus pumila in semiarid sandy land of northern China [J]. Trees - structure and function, 2014, 28: 41–52.

@Daniela Di Baccio : Thank you... Shall surely go through the papers suggested!

@ Hua Su: I m interested in knowing about the strategies...Shall definitely go through your publication... thank you very much.. :)