Materials 4 polyethylene tubes (5 cm diameter, 51

Materials
and Methods

Collection of Seaweed Materials

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Marine algae Ulva lactuca was collected
manually from Abu-Qir coast, Alexandria, Egypt during October 2015. The algae was then washed thoroughly with
filtered seawater many times to remove epiphytes and sands, then was brought to
the laboratory and washed thoroughly in tap water 3 to 4 times to remove excess
salt.

Preparation of Seaweed extract

The
washed and cleaned seaweed was shade-air dried for 2–4 days followed by oven drying for 12 h at 60 °C. The oven dried seaweed was hand
crushed and finely powdered with mixer-grinder. Of the dried material, 100 g
was extracted with 1000 mL of distilled water for 24 h. The contents were then
filtered through a double-layered muslin
cloth. The filtrate thus obtained was considered as 100% seaweed
aqueous extract. A 10%
extract concentration was prepared using double distilled
water and stored at 4 °C.

 

Plant material and experimental design

Zea
mays
grains (M10) were procured from the Crop Institute, Agricultural Research
Center, Giza, Egypt. The grains having the uniform size, shape, color and weight were selected for the study. Ten grains were arranged in 18-cm diameter Petri dishes
on two layers of filter paper (Whatman number 1) under normal laboratory
conditions at 20–23 °C day/14–16 °C night. Afterward, 15 mL
of distilled water was then added. Before sowing, the grains were surface
sterilized by soaking for 2 min in 4% sodium hypochlorite, then, rinsed four
times with double distilled water. Seven–day old seedlings were transferred to the
growth
units which consisted of 4 polyethylene tubes (5 cm diameter, 51 cm length).
Each tube had an out and inlet in order to circulate
the nutrient solution (Fig 1). The capacity
of each tube was 1500 mL with 31 pores (8 mm) distributed in two alternation
lines, where the seedlings should be settled. The micropipettes plastic tips
were used to support the seedlings during growth and when they were harvested.
An air pump terminal with a flow rate of 200
mL/min was used to aerate and circulate the
solution. The nutrient solution was completely renewed every three days.
The experiment was performed under normal laboratory conditions (20  ±2°C temperature, 75  ±2% relative humidity, and 14/10 h light/dark
photoperiod).

The
experimental design

Four
treatment groups were designed for the application of ULAE in the growth medium
of maize plant cultivated in the hydroponic system. The first group of
seedlings was grown in medium containing
50% of half-strength Hoagland’s solution
and 50% of ULAE (50% U + 50% H). The second group of seedlings was grown in a medium containing 25% of half-strength Hoagland’s solution and 75% of ULAE
(75% U + 25% H). Whereas, the third group of seedlings was grown in 100% half-strength Hoagland’s solution and were not treated with ULAE (control)
and seedlings of the fourth group were grown in ULAE alone (10%) served
as a positive control. In a parallel experiment,
four foliar applications consisting of
three different ULAE concentrations (0.5%, 1%, and 5%) and one control treatment (no spray) were given
to seedlings grown in the hydroponic system with half-strength Hoagland’s solution. About 50 mL of different
concentrations of the extract or water (for the control treatment) was given at
3 days intervals up to 14 days. After 14 days, the homogenous seedlings were
carefully collected from each treatment, and then gently blotted with filter
paper. The growth parameters such as root length, shoot length, fresh and dry
weight, and seedling length were recorded. The biochemical parameters including
chlorophyll a, b, and total chlorophyll content, carotenoid and Rubisco were
also analyzed. For the determination of seedlings, the dry weights samples were
dried at 65oC till constant weight. The experiment was carried out
in triplicate.

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