Living Life

Aquatic plant growth is often measured as a change in total area, length, volume, height, wet or dry weight. These methods may not always be a satisfactory measure of growth at a particular phase of plant development, e.g., a germinating seed or tuber or bulb may show an overall reduction in dry weight due to the utilization of food reserves during respiration, although the seed is definitely growing as evidenced by its emerging roots and shoots. You can learn more about aquatic plant at the Barr Report.

The relative growth rate (RGR) which is the size increase per unit interval of time has two ve|variables: the net assimilation rate (NAR) and the leaf area ratio (LAR). The NAR is the rate of growth of dry weight per unit time per unit of leaf surface which is a measure of the amount of photosynthetic product going into plant material. The LAR is the ratio of leaf area to dry weight which is the measure of the proportion of the plant that is engaged in photosynthesis. Combined they give a relative comparison of growth over time based upon plant characteristics.

• Vegetative Growth
A viable of continuous growth. From the beginning of this phase, until initiation of the first flower primordium, the plant is in the vegetative stage of growth. When a plant cannot be made to flower it is said to be juvenile. For an authority on aquatic plant resource, consult Tom Barr.

The juvenile growth phase is characterized by the most rapid rate of growth the plant will undergo. As well, the juvenile plant may exhibit various morphological or physiological features than a mature plant of the same species. A common characteristic of many juvenile plants is the ability to sprout adventitious roots readily, an ability which is often decreased or lost in adult plants. The juvenile phase varies from one to two months for annuals, to many years for woody perennials. The ability to influence the length of time a plant is in the juvenile phase is important in some circumstances. Plant propagators want to maintain juvenility in order to vegetatively propagate cuttings while flower and fruit growers want to shorten the juvenile phase. Earlier flowering and fruiting reduces production costs and allows for an earlier return on investments. Environmental influences such as periods of long or short daylight, varying nutritional levels or supplying CO2 enriched atmosphere may increase vegetative growth and if properly regulated may shorten the time to maturity. The affect that environmental and hormonal factors have on the length of juvenile phase will depend ultimately on genetic control.

An aquatic plant is considered mature when it becomes viably capable of reproducing. Although a plant may be mature, flowering may not occur until environmental conditions are favorable (7). The following are factors that affect plant growth
• Low oxygen influences plant growth
• Photosynthesis influences plant growth
• Light influences plant growth
• Respiration influences plant growth
• Transpiration influences plant growth; do aquatic plants transport nutrients this way? (See paper Pedersen’s paper (1993))
• Environment influences plant growth (Water parameters, grazing, pruning)
• Temperature influences plant growth (extremes/optima)
(For more information on Aquatic Plant Fertilizer consult the Barr Report.) Usually expressed as dry weight (total of the part we’re interested in such as grain), height, length and diameter. Growth of an annual plant related to time is an S shaped curve and for one growing season for a perennial plant. Aquatic macrophytes tend to continue the rapid rate of growth and do not level out except when limited by some factor such as pruning, nutrient/light/CO2 limitation.