Abstract:
Executive Summary
Bioregulators are vital in controlling plant growth and development. High temperature is a
severe environmental stressor that reduces crop yield. Tomato is one of the vegetable crops
whose growth, physiology, and yields are highly affected by high temperature. Despite the
importance of bioregulators in crop production, little information has been reported
concerning the effects of 4-Chlorophenoxyacetic acid (4-CPA), Naphthalene Acetic Acid
(NAA) and Gibberellic Acid (GA
) during the summer season in Bangladesh. As a result,
possible morpho-physiological and yield responses of summer tomato (BARI Hybrid
Tomato-10) to bioregulators were investigated at the Central Research Farm of Sher-eBangla
Agricultural University, Dhaka. In this study, the external application of 4-CPA,
NAA and GA
3
3
was used to find the response of summer tomato under field condition in the
summer season. The pot experiment was arranged under a Completely Randomized Design
(CRD) containing three replications. The bioregulator concentrations consisted of control, 20
ppm 4-CPA, 40 ppm 4-CPA, 60 ppm 4-CPA, 10 ppm NAA, 20 ppm NAA, 30 ppm NAA, 20
ppm GA
3
, 30 ppm GA
3
and 40 ppm GA
. The different concentrations of bioregulators
showed potential influence to enhance plant height (36.02%), number of branches plant-1
(50%), number of leaves plant-1 (50%), chlorophyll a content (46.95%), chlorophyll b
content (27.97%), total chlorophyll content (38.49%), number of flower cluster plant-1
(67.02%), number of flower plant-1 (50%), number of fruits plant-1 (48.72%) and fruit
weight plant-1 (64.18%) compared to control treatment. Among the bioregulators, 20 ppm
NAA showed better result to reduce flower and fruit dropping of summer tomato. The
findings of the study imply that bioregulators can be utilized as a protective agent to reduce
the negative effects of high temperature on tomato growth and physiology, resulting in
optimum yield.
