Ecological Forms of Plants
When plants adapt to the particular environment conditions, leaves usually re-spond first. Conversely, one can estimate the ecology of plant simply looking on its leaves.
In regards to water, there are four main types of plants: xerophytes, mesophytes, hygrophytes, and hydrophytes. Xerophytes are adapted to the scarce water (Fig. 5.17), they could be sclerophytes (usually with prickly and/or rich of scle-renchyma leaves) and succulents (with water-accumulating stems or leaves). Mesophytes are typical plants which adapt to regular water. Hygrophytes live in constantly wet environment, their leaves adapted to high transpiration and sometimes even to guttation (excretion of water drops). Hydrophytes grow in water, their leaves are frequently highly dissected to access more gases dissolved in water, and their leaf petioles and stems have air canals to supply underwater organs with gases.
In regards to light, plants could be sciophytes or heliophytes. Sciophytes prefer the shade to sunlight, their leaves contain mostly spongy mesophyll. Helio-phytes prefer the full sun and therefore have leaves filled with palisade meso-phyll. The intermediate group are “partial shade” plants.
Halophytes, nitrate halophytes, oxylophytes, and calciphytes are ecological groups adapted to the over-presence of particular chemicals. Halophyte plants are frequent, they accumulate (and look similarly to succulents), excrete or avoid (which looks like sclerophyte) sodium chloride (NaCl). They grow in salty places: sea shores, salt deserts and solonets prairies. Nitrate halophyte plants grow on soils rich in NaNO3. Oxylophytes grow in acidic soils, whereas calciphytes grow in basic, chalk soils rich in CaCO3.
Leaves will also reflect adaptations to the substrate, ecological forms named psammophytes (grow on sand), petrophytes (grow on rocks), and rheophytes (grow in fast springs). The latter plants frequently have serious simplifications in their body plan, their leaves and stems are often reduced to form a thallus-like body.
Parasitic plants could be classified in mycoparasites, hemiparasites, and phy-toparasites. Mycoparasitic plants feed on soil fungi, phytoparasitic plants are either plant root parasites or plant stem parasites lacking chlorophyll and pho-tosynthesis. Hemiparasitic plants are those which still have chloroplasts but take the significant part of water and even organic compounds from the host plant (like mistletoe, Viscum).