A plant nutrient is a chemical element that is essential for plant growth and reproduction. Essential
element is a term often used to identify a plant nutrient. The term nutrient implies essentiality, so it
is redundant to call these elements essential nutrients. Commonly, for an element to be a nutrient,
it must fit certain criteria. The principal criterion is that the element must be required for a plant to
complete its life cycle. The second criterion is that no other element substitutes fully for the element
being considered as a nutrient.
The last decade has contributed significantly to the development of research on the
biogeochemistry of tropical mangrove ecosystems. Also obvious during the last
decade is the continued and dramatic destruction of natural tropical mangrove
resources in Southeast Asia (Fig. 1.1). The naturally high productivity of tropi-
cal mangroves has traditionally been exploited for a wide variety of purposes,
both as sources of forestry or fisheries products and they have also been used
for human settlement (Hatcher et al., 1989; Platong, 1998).
Results from this laboratory can be used for a discussion of the biological consequences of
pollution and will provide students with an appreciation for how dilution influences a chemical's
biological effect. While endocrine disrupters are currently a 'hot topic,' other pollutants could also
be tested. We tested some heavy metals (which are a perennial concern) and had some very
interesting growth abnormalities show up. Chemical pollutants are not the only parameters that may
influence sponge growth.
Physical activity in childhood is important for many reasons and a variety of sources indicate
a direct relationship between physical activity and children’s health (Hope and others 2007). In
early childhood physical exercise helps build strong bones, muscle strength and lung capacity
(Lindon 2007). It may also increase cognitive function, improve academic achievement and
accelerate neurocognitive processing. In addition, it appears that active children are also
less likely to smoke, to abuse alcohol or take illegal drugs as they grow up (BHF 2009).